Acknowledgements

We would like to acknowledge the help we have received over the years from our general practitioner, medical student, and

ophthalmological colleagues for their probing questions that have helped us crystallise our thoughts on many topics. We are grateful

to Alan Lacey from the Department of Medical Illustration at Moorfields Eye Hospital for his superb artistry and the diagrams. We

would also like to thank Peggy Khaw for her tremendous work on the many drafts of the book from its inception, and Jennifer Murray

for her help with the 4th edition. In the past Jane Smith, Mary Evans, Mary Banks, Deborah Reece, Alex Stibbe, and currently Eleanor

Lines and Sally Carter have also been very supportive, steering us through the pitfalls of publishing. We also thank Steve Tuft for his

expert advice on the refractive surgery section and Marie Tsaloumas for the photographs of age-related macular degeneration. Jackie

Martin (supported by the Royal London Society for the Blind), Barbara Norton, and Jennifer Rignold guided us through the services

for the visually handicapped. We thank Pharmacia (now Pfizer) for permission to use their colour plates on cataract surgery

(page 48), Guide Dogs for the Blind for the picture of the guide dog (page 43), and Simon Keightley of the DVLA for his advice on

driving standards. We are grateful to many people and organisations for use of their photographs in Chapter 14. These include the

International Resource Centre for the Prevention of Blindness at the International Centre for Eye Health, London School of

Hygiene and Tropical Medicine, London; Sue Stevens; John DC Anderson; Pak Sang Lee; Murray McGavin; Hugh Taylor; the

Christoffel-Blindenmission (CBM); and the World Health Organization (the photograph of corneal melt on page 83 is from their

Primary Eye Care slide set). The map on page 83 showing areas affected by onchoceriasis is adapted from a slide from the Image

Bureau. Most of the photographs are copyright of Professor Peng Khaw. Some photographs are copyright of Moorfields Eye Hospital

NHS Trust. The photograph of postoperative glaucoma drainage bleb on page 85 is copyright of City Hospital NHS Trust,

Birmingham. We would like to acknowledge the support of the Michael and Ilse Katz Foundation.

PTK

A R E

2004

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vii

History and examination

History

Visual symptoms: details to establish

●

Monocular or binocular

As in all clinical medicine, an accurate history and examination

●

Type of disturbance

are essential for correct diagnosis and treatment. Most ocular

●

Rate of onset

conditions can be diagnosed with a good history and simple

●

Presence and type of field loss

examination techniques. Conversely, the failure to take a history

●

Associated symptoms—for example, flashing lights or floaters

and perform a simple examination can lead to conditions being

●

Effect on lifestyle

missed that pose a threat to sight, or even to life.

●

Specific worries

The history may give many clues to the diagnosis. Visual

symptoms are particularly important.

The rate of onset of visual symptoms gives an indication of

the cause. A sudden deterioration in vision tends to be vascular

in origin, whereas a gradual onset suggests a cause such as

cataract. The loss of visual field may be characteristic, such as

the central field loss of macular degeneration. Symptoms such

as flashing lights may indicate traction on the retina and

impending retinal detachment. Difficulties with work, reading,

watching television, and managing in the house should be

Vision

identified. It is particularly important to assess the effect of the

Working

visual disability on the patient’s lifestyle, especially as conditions

Reading

Watching television

such as cataracts can, with modern techniques, be operated on

at an early stage.

Drug history

Family history

The patient should also be asked exactly what is worrying

Chloroquine

Glaucoma

them, as visual symptoms often cause great anxiety. Appropriate

Squint

reassurance then can be given.

Questions about particular symptoms

Ophthalmic history

Some specific questions are important in certain circumstances.

Examples of specific questions

A history of ocular trauma or any high velocity injury—

particularly a hammer and chisel injury—should suggest an

intraocular foreign body. Other questions, for example about

the type of discharge in a patient with a red eye, may enable

Medical history

Ocular history

you to make the diagnosis.

Diabetes—

Shortsighted—

vitreous haemorrhage

retinal detachment

Previous ocular history

Special questions

Easily forgotten, but essential. The patient’s red eye may be

Hammer and chisel injury—

associated with complications of contact lens wear—for

foreign body

Discharge—

example, allergy or a corneal abrasion or ulcer. A history of

infection

severe shortsightedness (myopia) considerably increases the

risk of retinal detachment. A history of longsightedness

Answers to specific questions in the ophthalmic history will give

(hypermetropia) and typically the use of reading glasses before

clues to the diagnosis and help to exclude other problems

the age of 40 increases the risk of angle closure glaucoma.

Patients often forget to mention eye drops and eye operations

if they are asked just about “drugs and operations.” A purulent

conjunctivitis requires much more urgent attention if the

patient has previously had glaucoma drainage surgery, because

of the risk of infection entering the eye.

A history of a lazy eye (amblyopia) in a patient with a

problem with their effective “only” eye is extremely

Medical history

important, as disturbance of vision in the good eye would

Many systemic disorders affect the eye, and the medical history

result in definite functional impairment

may give clues to the cause of the problem; for instance,

diabetes mellitus in a patient with a vitreous haemorrhage or

sarcoidosis in a patient with uveitis.

Family history

A good example of the importance of the family history is in

A family history of glaucoma is a risk factor for the

primary open angle glaucoma. This may be asymptomatic until

development of glaucoma

severe visual damage has occurred. The risk of the disease may

be as high as 1 in 10 in first degree relatives, and the disease

may be arrested if treated at an early stage. For any disease that

ABC of Eyes

has a genetic component (for example, glaucoma), the age of

Assessment of vision

onset and the severity of disease in affected family members

●

Snellen chart at 6 m

can be very useful information.

●

Snellen chart closer

●

Counting fingers

Drug history

●

Hand movements

Many drugs affect the eye, and they should always be considered

●

Perception of light

as a cause of ocular problems; for example, chloroquine may

●

No perception of light

affect the retina. Steroid drugs in many different forms (drops,

ointments, tablets, and inhalers) may all lead to steroid induced

glaucoma.

Examination of the visual system

Vision

An assessment of visual acuity measures the function of the eye

and gives some idea of the patient’s disability. It may also have

considerable medicolegal implications; for example, in the case

of ocular damage at work or after an assault.

In the United Kingdom, visual acuity is checked with a

standard Snellen chart at 6 m. If the room is not large enough, a

mirror can be used with a reversed Snellen chart at 3 m. The

numbers next to the letters indicate the distance at which a

person with no refractive error can read that line (hence the 6/60

line should normally be read at 60 m). If the top line cannot be

discerned, the test can be done closer to the chart. If the chart

cannot be read at 1 m, patients may be asked to count fingers,

and, if they cannot do that, to detect hand movements. Finally, it

may be that they can perceive only light. From the patient’s point

of view, the functional difference between these categories may be

Testing reading vision

Visual acuity chart

the difference between managing at home on their own (count

fingers) and total dependence on others (perception of light).

In other areas of the world (for example, the United

States), visual acuity charts use a different nomenclature. Visual

acuity of 20/20 is equivalent to 6/6 and 20/200 is equivalent to

6/60. A logarithmic chart (LogMAR) is also used, especially for

large scale clinical trials and orthoptic childhood screening.

The LogMAR system offers increased sensitivity in acuity

testing, but the tests take longer to perform.

Vision should be tested with the aid of the patient’s usual

glasses or contact lenses. To achieve optimal visual acuity, the

patient should be asked to look through a pinhole. This

reduces the effect of any refractive error and particularly is

useful if the patient cannot use contact lenses because of a red

eye or has not brought their glasses. If patients cannot read

English, they can be asked to match letters; this is also useful

Ishihara colour plate. If a person is

for young children.

colour blind they cannot see the

number

Reading vision can be tested with a standard reading type

book or, if this is not available, various sizes of newspaper print.

There may be quite a difference in the near and distance

vision. A good example is presbyopia, which usually develops in

the late forties because of the failure of accommodation with

age. Distance vision may be 6/6 without glasses, but the patient

may be able to read only larger newspaper print.

Colour vision can be tested by using Ishihara colour plates,

which may give useful information in cases of inherited and

acquired abnormalities of colour vision. The ability to detect

relative degrees of image contrast (contrast sensitivity) is also

important and can be assessed with a Pelli-Robson chart. Some

eye problems (such as cataract, for example) may cause a

significant reduction in contrast sensitivity, despite good Snellen

visual acuity.

Field of vision

Testing the visual field. Ask the patient to cover the

Tests of the visual field may give clues to the site of any lesion

eye not being tested. Ensure that the eye is completely

and the diagnosis. It is important to test the visual field in any

covered by the palm

History and examination

patient with unexplained visual loss. Patients with lesions that

affect the retrochiasmal visual pathway may find it difficult to

verbalise exactly why their vision is “not right.”

Location of the lesion—Unilateral field loss in the lower nasal

field suggests an upper temporal retinal lesion. Central field

loss usually indicates macular or optic nerve problems.

A homonymous hemianopia or quadrantanopia indicates

problems in the brain rather than the eye, although the patient

may present with visual disturbance.

Diagnosis—A bitemporal field defect is most commonly

caused by a pituitary tumour. A field defect that arches over

central vision to the blind spot (arcuate scotoma) is almost

pathognomonic of glaucoma.

To test the visual field—The patient should be seated directly

opposite the examiner and then should be asked to cover the

eye that is not being tested and to look at the examiner’s face.

It is essential to make sure that the other eye is covered

properly to eliminate erroneous results. In case of a gross

defect, the patient will not be able to see part of the examiner’s

face and may be able to indicate this precisely: “I can’t see the

centre of your face.”

Using a readily available red target (for example, a tropicamide bottle top)

If no gross defect is present, the fields can be tested more

to test the visual field

formally. Testing the visual field with peripheral finger

movements will show severe defects, but a more sensitive test is

the detection of red colour, because the ability to detect red tends

to be affected earlier. A red pin is moved in from the periphery

An extremely sensitive test of the fields is the comparison

and the patient is asked when they can see something red.

of the red in different quadrants. A good example is a

patient who may have clinical signs of pituitary disease

The pupils

such as acromegaly; an early temporal defect can be

detected if the patient is asked to compare the “quality” of

Careful inspection of the pupils can show signs that are helpful

the red colour in the upper temporal and nasal fields

in diagnosis. A bright torch is essential. A pupil stuck down to

the lens is a result of inflammation within the eye, which always

is serious. A peaked pupil after ocular injury suggests

perforation with the iris trapped in the wound. A vertically oval

Abnormal pupil reactions in the presence of ocular

unreactive pupil may be seen in acute closed angle glaucoma.

symptoms always should be treated seriously

The pupil’s reaction to a good light source is a simple way

of checking the integrity of the visual pathways. When testing

the direct and consensual pupil reactions to light, the

illumination in the room should be reduced and the patient

should focus on a distant point. By the time pupils do not react

to direct light, the damage is very severe. A much more

sensitive test is the relative difference in pupillary reactions.

Move the torchlight to and fro between the eyes, not allowing

time for the pupils to dilate fully. If one of the pupils continues

to dilate when the light shines on it, there is a defect in the

visual pathway on that side (relative afferent pupillary defect).

Cataracts and macular degeneration do not usually cause an

afferent pupillary defect unless the lesions are particularly

advanced. Neurological disease must be suspected.

Other important and potentially life threatening conditions

in which the pupils are affected include Horner’s syndrome,

Torn peripheral iris

(iridodialysis)

where the pupil is small but reactive with an associated ptosis.

This condition may be caused by an apical lung carcinoma. The

well known Argyll Robertson pupils caused by syphilis (bilateral

small irregular pupils with light-near dissociation) are rare. In a

third nerve palsy there is ptosis and the eye is divergent. The

pupil size and reactions in such a case give important clues to

the aetiology. If the pupil is unaffected (“spared”), the cause is

likely to be medical—for example, diabetes or hypertension. If

the pupil is dilated and fixed, the cause is probably surgical—

for example, a treatable intracranial aneurysm.

Any differences in the colour of the two irides

(heterochromia iridis) should be noted as this may indicate

congenital Horner’s syndrome, certain ocular inflammatory

conditions (Fuch’s heterochromic cyclitis), or an intraocular

Distorted pupil after broad

foreign body.

iridectomy

ABC of Eyes

Eye position and movements

The appearance of the eyes shows the presence of any large

degree of misalignment. This can, however, be misleading if the

medial folds of the eyelids are wide. The position of the corneal

reflections helps to confirm whether there is a true “squint.”

Squints and cover tests are dealt with in Chapter 11.

Patients should be asked if they have any double vision. If

so, they should be asked to say whether diplopia occurs in any

particular direction of gaze. It is important to exclude palsies of

the third (eye turned out) or sixth (failure of abduction)

cranial nerves, as these may be secondary to life threatening

conditions. Complex abnormalities of eye movements should

Eye movements

lead you to suspect myasthenia gravis or dysthyroid eye disease.

The presence of nystagmus should be noted, as it may indicate

Test movements in all directions

significant neurological disease.

and also convergence

A protruding globe (proptosis) or a sunken globe

Ask about double vision: if present,

in which direction of gaze is it most

(enophthalmos) should be recorded. Proptosis is always an

pronounced?

Look for nystagmus

important finding: its rate of onset and progression may give

clues to the underlying pathology, and the direction of globe

displacement indicates the site of the pathology.

Convergence

Test eye movements in all directions and when

converging

The cornea should be stained with fluorescein eye drops.

Normal position of corneal light reflexes

If this is not done, many lesions, including large corneal

ulcers, may be missed

Eyelids, conjunctiva, sclera, and cornea

Examination of the eyelids, conjunctiva, sclera, and cornea

should be performed in good light and with magnification. You

will need:

●

a bright torch (with a blue filter for use with fluorescein) or

an ophthalmoscope with a blue filter

●

a magnifying aid.

The lower lid should be gently pulled down to show the

conjunctival lining and any secretions in the lower fornix.

Corneal abrasion stained with

The anterior chamber should be examined, looking

fluorescein and illuminated with

specifically at the depth (a shallow anterior chamber is seen in

blue light

angle-closure glaucoma and perforating eye injuries) and for

the presence of pus (hypopyon) or blood (hyphaema). All

these signs indicate serious disease that needs immediate

ophthalmic referral.

Eyelids—Compare both sides and note position, lid

If there are symptoms of “grittiness,” a red eye or any

lesions, and conditions of margins

history of foreign body, the upper eyelid should be everted.

Ectropion

Basal cell carcinoma

Blepharitis

History and examination

This should not be done, however, if there is any question of

ocular perforation, as the ocular contents may prolapse.

Conjunctiva and sclera—Look for local or generalised

inflammation and pull down the lower lid and evert upper lid.

Cornea—Look at clarity and stain with fluorescein.

Anterior chamber—Check for blood and pus; also check

chamber depth.

The drainage angle of the eye can be checked with a special

Scleritis: localised redness

lens (gonioscope).

Conjunctivitis: generalised

Blood in anterior chamber

redness

(hyphaema)

Intraocular pressure

Assessment of intraocular pressure by palpation is useful only

when the intraocular pressure is considerably raised, as in acute

closed angle glaucoma. The eye should be gently palpated

between two fingers and compared with the other eye or with

the examiner’s eye. The eye with acute glaucoma feels hard.

Consider acute angle closure in any person over the age of 50

with a red eye.

Special contact lens being used to view the drainage angle of the eye

(gonioscope)

Ophthalmoscopy

Good ophthalmoscopy is essential to avoid missing many

serious ocular and general diseases. A direct ophthalmoscope

can be used to allow intraocular structures to be seen. Specific

contact and non-contact lenses are used during the

examination, and the ophthalmologist should use a slit-lamp

microscope or head-mounted ophthalmoscope.

To get a good view, the pupil should be dilated. There is an

associated risk of precipitating acute angle closure glaucoma,

but this is very small. The best dilating drop is tropicamide 1%,

which is short acting and has little effect on accommodation.

However, the effects may still last several hours, so the patient

should be warned about this and told not to drive until any

blurring of vision has subsided.

The direct ophthalmoscope should be set on the “0” lens.

Measuring intraocular pressure

The patient should be asked to fix their gaze on an object in

by applanation tonometry

the distance, as this reduces pupillary constriction and

accommodation, and helps keep the eye still. To enable a

patient to fix on a distant object with the other eye, the

examiner should use his right eye to examine the patient’s

right eye, and vice versa. The light should be shone at the eye

until the red reflex is elicited. This red reflex is the reflection

from the fundus and is best assessed from a distance of about

50 cm. If the red reflex is either absent or diminished, this

indicates an opacity between the cornea and retina. The most

common opacity is a cataract.

The optic disc should then be located and brought into

Patients should always be warned to seek help immediately

focus with the lenses in the ophthalmoscope. If a patient has a

if they have symptoms of pain or haloes around lights,

high refractive error, they can be asked to leave their glasses on,

after having their pupils dilated

although this can cause more reflections. The physical signs at

the disc may be the only chance of detecting serious disease

in the patient. The retina should be scanned for abnormalities

such as haemorrhages, exudates, or new vessels. The green

filter on the ophthalmoscope helps to enhance blood vessels

and microaneurysms. Finally the macula should be examined

ABC of Eyes

for the pigmentary changes of age-related macular

degeneration and the exudates of diabetic maculopathy.

It is viewed using a slit-lamp microscope and lens or head

mounted indirect ophthalmoscope. However, these techniques

are specialised.

Slit-lamp and 78 dioptre lens used to examine the retina

Indirect ophthalmoscopy

Optic disc, retina, and macula

Physical signs of disease at the disc

●

A blurred disc edge may be the only sign of a cerebral tumour

●

Cupping of the optic disc may be the only sign of undetected

primary open angle glaucoma

●

New vessels at the disc may herald blinding proliferative

retinopathy in a patient without symptoms

●

A pale disc may be the only stigma of past attacks of optic

neuritis or of a compressive cerebral tumour

Normal optic disc with a healthy

New vessels on optic disc in diabetes

Optic atrophy—pale disc

pink rim

Glaucomatous cupping—displacement

Age-related macular degeneration—

Diabetic maculopathy—oedema,

of vessels and pale disc

deposits in macular area

exudates, and haemorrhages

Red eye

The “red eye” is one of the most common ophthalmic

Equipment for an eye examination

problems presenting to the general practitioner. An accurate

●

Snellen eye chart

history is important and should pay particular attention to

●

Bright torch or ophthalmoscope with blue

vision, degree, and type of discomfort and the presence of a

filter

discharge. The history, and a good examination, will usually

●

Magnifying aid—for example, loupe

permit the diagnosis to be made without specialist ophthalmic

●

Paper clip to help lid eversion

equipment.

●

Fluorescein impregnated strips or eye drops

Symptoms and signs

The most important symptoms are pain and visual loss; these

suggest serious conditions such as corneal ulceration, iritis,

and acute glaucoma. A purulent discharge suggests bacterial

conjunctivitis; a clear discharge suggests a viral or allergic

cause. A gritty sensation is common in conjunctivitis, but a

foreign body must be excluded, particularly if only one eye is

affected. Itching is a common symptom in allergic eye disease,

blepharitis, and topical drop hypersensitivity.

Corneal abscess (Pseudomonas) in contact

Corneal abrasions will be missed if fluorescein is not used

lens wearer

Ciliary flush

Papillae

Irregular

Vesicles

Follicles

pupil

Foreign body

Anterior uveitis with ciliary flush around

cornea and irregular stuck down pupil

Yellow

Hypopyon

Dilated

discharge

episcleral

vessels

Dilated

Corneal ulcer

Dendritic

conjunctival

ulcer

vessels

Scleritis—deeply injected and usually painful

Important physical signs to look for in a patient with a red eye

Acute angle closure glaucoma with red eye,

Bacterial conjunctivitis without discharge

Foreign body

semidilated pupil, and hazy cornea

ABC of Eyes

Conjunctivitis

Conjunctivitis is one of the most common causes of an

uncomfortable red eye. Conjunctivitis itself has many causes,

including bacteria, viruses, Chlamydia, and allergies.

Bacterial conjunctivitis

History—The patient usually has discomfort and a purulent

discharge in one eye that characteristically spreads to the other

eye. The eye may be difficult to open in the morning because

the discharge sticks the lashes together. There may be a history

of contact with a person with similar symptoms.

Examination—The vision should be normal after the

discharge has been blinked clear of the cornea. The discharge

Purulent bacterial conjunctivitis

usually is mucopurulent and there is uniform engorgement of

all the conjunctival blood vessels. When fluorescein drops are

instilled in the eye there is no staining of the cornea.

Management—Topical antibiotic eye drops (for example,

chloramphenicol) should be instilled every two hours for the

first 24 hours to hasten recovery, decreasing to four times a day

for one week. Chloramphenicol ointment applied at night may

also increase comfort and reduce the stickiness of the eyelids in

the morning. Patients should be advised about general hygiene

measures; for example, not sharing face towels.

Viral conjunctivitis

Viral conjunctivitis commonly is associated with upper

respiratory tract infections and is usually caused by an

adenovirus. This is the type of conjunctivitis that occurs in

epidemics of “pink eye.”

History—The patient normally complains of both eyes being

gritty and uncomfortable, although symptoms may begin in one

Adenovirus conjunctivitis of the right eye and enlarged

eye. There may be associated symptoms of a cold and a cough.

preauricular nodes

The discharge is usually watery.

Viral conjunctivitis usually lasts longer than bacterial

conjunctivitis and may go on for many weeks; patients need

to be informed of this. Photophobia and discomfort may be

severe if the patient goes on to develop discrete corneal

opacities.

Examination—Both eyes are red with diffuse conjunctival

injection (engorged conjunctival vessels) and there may be a

clear discharge. Small white lymphoid aggregations may be

present on the conjunctiva (follicles). Small focal areas of

corneal inflammation with erosions and associated opacities

may give rise to pronounced symptoms, but these are difficult

Viral conjunctivitis

to see without high magnification. There may be associated

head and neck lymphadenopathy with marked pre-auricular

lymphadenopathy.

Management—Viral conjunctivitis is generally a self limiting

condition, but antibiotic eye drops (for example,

chloramphenicol) provide symptomatic relief and help prevent

secondary bacterial infection. Viral conjunctivitis is extremely

contagious, and strict hygiene measures are important for both

the patient and the doctor; for example, washing of hands and

sterilising of instruments. The period of infection is often

longer than with bacterial pathogens and patients should be

warned that symptoms may be present for several weeks. In

some patients the infection may have a chronic, protracted

Chronic adenovirus infection

course and steroid eye drops may be indicated if the corneal

lesions and symptoms are persistent.

Steroids must only be prescribed with ophthalmological

Topical steroids should not be prescribed

supervision, because of the real danger of causing cataract or

or continued without continuous

irreversible glaucomatous damage. Furthermore, if long term

ophthalmological supervision—potentially

steroids are required, patients should remain under continuous

blinding complications may occur

ophthalmological supervision.

Red eye

Chlamydial conjunctivitis

History—Patients usually are young with a history of a chronic

bilateral conjunctivitis with a mucopurulent discharge. There

may be associated symptoms of venereal disease. Patients

generally do not volunteer genitourinary symptoms when

presenting with conjunctivitis; these need to be elicited through

questioning.

Examination—There is bilateral diffuse conjunctival

injection with a mucopurulent discharge. There are many

lymphoid aggregates in the conjunctiva (follicles). The cornea

usually is involved (keratitis) and an infiltrate of the upper

cornea (pannus) may be seen.

Management—The diagnosis is often difficult and special

Chlamydial conjunctivitis—exclude associated venereal

bacteriological tests may be necessary to confirm the clinical

disease

suspicions. Treatment with oral tetracycline or a derivative for

at least one month can eradicate the problem, but poor

compliance can lead to a recurrence of symptoms. Systemic

tetracycline can affect developing teeth and bones and should

not be used in children or pregnant women.

Associated venereal disease should also be treated, and it is

important to check the partner for symptoms or signs of

venereal disease (affected females may be asymptomatic). It

often is helpful to discuss cases with a genitourinary specialist

before commencing treatment, so that all relevant

microbiological tests can be performed at an early stage.

Trachoma—scarred tarsal plate

In developing countries, infection by Chlamydia trachomatis

results in severe scarring of the conjunctiva and the underlying

tarsal plate. These cicatricial changes cause the upper eyelids

to turn in (entropion) and permanently scar the already

damaged cornea. Worldwide, trachoma is still one of the major

causes of blindness.

Conjunctivitis in infants

Conjunctivitis in young children is extremely important

because the eye defences are immature and a severe

conjunctivitis with membrane formation and bleeding may

occur. Serious corneal disease and blindness may result.

Conjunctivitis in an infant less than one month old (ophthalmia

neonatorum) is a notifiable disease. Such babies must be seen

in an eye department so that special cultures can be taken and

appropriate treatment given. Venereal disease in the parents

must be excluded.

Infantile conjunctivitis—notifiable disease

Allergic conjunctivitis

History—The main feature of allergic conjunctivitis is itching.

Both eyes usually are affected and there may be a clear

discharge. There may be a family history of atopy or recent

contact with chemicals or eye drops. Similar symptoms may

have occurred in the same season in previous years. It is

important to differentiate between an acute allergic reaction

and a more long term chronic allergic eye disease.

Examination—The conjunctivae are diffusely injected and

may be oedematous (chemosis). The discharge is clear and

stringy. Because of the fibrous septa that tether the eyelid

Chemosis due to pollen allergy

(tarsal) conjunctivae, oedema results in round swellings

(papillae). When these are large they are referred to as

cobblestones.

Management—Topical antihistamine and vasoconstrictor eye

drops provide short term relief. Eye drops that prevent

degranulation of mast cells also are useful, but they may need

to be used for several weeks or months to achieve maximal

effect. Oral antihistamines may also be used, particularly the

newer compounds that cause less sedation. Topical steroids are

effective but should not be used without regular

ophthalmological supervision because of the risk of steroid

induced cataracts and glaucoma, which may irreversibly

Large papillae in allergic conjunctivitis

ABC of Eyes

damage vision. Cases of allergic eye disease in association with

severe eczema will often need careful combined

ophthalmological and dermatological management.

Sclera

Eyelid (tarsal)

Episcleritis and scleritis

conjunctiva

Cornea

Episcleritis and scleritis usually present as a localised area of

Ocular (bulbar)

conjunctiva

Episclera

inflammation. The episclera lies just beneath the conjunctiva

and adjacent to the tough white scleral coat of the eye. Both

the sclera and episclera may become inflamed, particularly in

Conjunctiva,

rheumatoid arthritis and other autoimmune conditions, but no

sclera, and

episclera

cause is found for most cases of episcleritis.

History—The patient complains of a red and sore eye that

may also be tender. There may be reflex lacrimation but usually

there is no discharge. Scleritis is much more painful than

episcleritis. The pain of scleritis often is sufficiently severe to

wake the patient at night.

Examination—There is a localised area of inflammation that

is tender to the touch. The episcleral and scleral vessels are

larger than the conjunctival vessels. The signs of inflammation

are usually more florid in scleritis.

Management—Any underlying cause should be identified.

Episcleritis

Episcleritis is essentially self limiting, but steroid eye drops

hasten recovery and provide symptomatic relief. Scleritis is

much more serious, and all patients need ophthalmological

review. Serious systemic disorders need to be excluded, and

systemic immunosuppressive treatment may be required.

Corneal ulceration

Corneal ulcers may be caused by bacterial, viral, or fungal

infections; these may occur as primary events or may be

secondary to an event that has compromised the eye—for

Scleritis

example, abrasion, wearing contact lenses, or use of topical

steroids.

History—Pain usually is a prominent feature as the cornea

is an exquisitely sensitive structure, although this is not so when

corneal sensation is impaired; for example, after herpes zoster

ophthalmicus. Indeed, this lack of sensory innervation may be

the cause of the ulceration. There may be clues such as similar

past attacks, facial cold sores, a recent abrasion, or the wearing

of contact lenses.

Eye with herpes simplex

Examination—Visual acuity depends on the location and size

ulcer (not visible without

fluorescein)

of the ulcer, and normal visual acuity does not exclude an ulcer.

There may be a watery discharge due to reflex lacrimation or

a mucopurulent discharge in bacterial ulcers. Conjunctival

injection may be generalised or localised if the ulcer is peripheral,

giving a clue to its presence. Fluorescein must be used or an ulcer

easily may be missed. Certain types of corneal ulceration are

characteristic; for example, dendritic lesions of the corneal

epithelium usually are caused by infection with the herpes

Same eye stained with

fluorescein and viewed with

simplex virus. If there is inflammation in the anterior chamber

blue light (ulcer visible)

there may be a collection of pus present (hypopyon). The upper

eyelid must be everted or a subtarsal foreign body causing corneal

ulceration may be missed. Patients with subtarsal foreign bodies

sometimes do not recollect anything entering the eye.

Management—Patients with corneal ulceration should be

referred urgently to an eye department or the eye may be lost.

Management depends on the cause of the ulceration. The

diagnosis usually will be made on the clinical appearance.

The appropriate swabs and cultures should be arranged to

Herpes simplex ulcers

try to identify the causative organism.

inadvertently treated with

Intensive treatment then is started with drops and ointment

steroids. Ulceration has

of broad spectrum antibiotics until the organisms and their

spread and deepened

Red eye

sensitivities to various antibiotics are known. Injections of

antibiotics into the subconjunctival space may be given to

increase local concentrations of the drugs.

Topical antiviral therapy should be used for herpetic

infections of the cornea. Cycloplegic drops are used to relieve

pain resulting from spasm of the ciliary muscle, and as they are

also mydriatics they prevent adhesion of the iris to the lens

(posterior synechiae). Topical steroids may be used to reduce

local inflammatory damage not caused by direct infection, but

the indications for their use are specific and they should not be

used without ophthalmological supervision.

Corneal abscess with pus in anterior chamber

(hypopyon)

Iritis, iridocyclitis, anterior uveitis,

and panuveitis

The iris, ciliary body, and choroid are similar embryologically

and are known as the uveal tract. Inflammation of the iris

(iritis) does not occur without inflammation of the ciliary body

(cyclitis) and together these are referred to as iridocyclitis or

Sclera

anterior uveitis. Thus the terms are synonymous. It is important

to consider diabetes mellitus in any patient with recent onset

Cornea

anterior uveitis.

Retina

Several groups of patients are at risk of developing anterior

uveitis, including those who have had past attacks of iritis and

Iris

those with a seronegative arthropathy, particularly if they are

positive for the HLA B27 histocompatibility antigen; for

example, a young man with ankylosing spondylitis. Children

Ciliary body

Choroid

with seronegative arthritis are also at high risk, particularly

if only a few joints (pauciarticular) are affected by the

(Anterior uvea)

(Posterior uvea)

arthritis.

Uveitis in children with juvenile chronic arthritis may be

Uveal tract

relatively asymptomatic and they may suffer serious ocular

damage if they are not screened. Sarcoidosis also causes

Different parts of the eye that may be affected by uveitis

chronic anterior uveitis, as do several other conditions

including herpes zoster ophthalmicus, syphilis, and tuberculosis.

In panuveitis both the anterior and posterior segments of

the eyes are inflamed and patients may have evidence of an

associated systemic disease (for example, sarcoidosis, Behçet’s

syndrome, systemic lupus erythematosus, polyarteritis nodosa,

Wegener’s granulomatosis, or toxoplasmosis).

History—The patient who has had past attacks can often feel

an attack coming on even before physical signs are present.

There is often pain in the later stages, with photophobia due to

inflammation and ciliary spasm. The pain may be worse when

the patient is reading and contracting the ciliary muscle.

Examination—The vision initially may be normal but later it

may be impaired. Accommodation, and hence reading vision,

may be affected. There may be inflammatory cells in the

Anterior uveitis or iritis with ciliary flush but

anterior chamber, cataracts may form, and adhesions may

pupil not stuck down

develop between the iris and lens. The affected eye is red with

the injection particularly being pronounced over the area that

covers the inflamed ciliary body (ciliary flush). The pupil is

small because of spasm of the sphincter, or irregular because of

adhesions of the iris to the lens (posterior synechiae). An

abnormal pupil in a red eye usually indicates serious ocular

disease. Inflammatory cells may be deposited on the back of

the cornea (keratitic precipitates) or may settle to form a

collection of cells in the anterior chamber of the eye

(hypopyon).

Management—If there is an underlying cause it must be

treated, but in many cases no cause is found. It is important to

ensure there is no disease in the rest of the eye that is giving

rise to signs of an anterior uveitis, such as more posterior

inflammation, a retinal detachment, or an intraocular tumour.

Anterior uveitis with ciliary flush and

Treatment is with topical steroids to reduce the inflammation

irregular pupil

ABC of Eyes

and prevent adhesions within the eye. The ciliary body is

paralysed to relieve pain, and the associated dilation of the

pupil also prevents the development of adhesions between the

iris and the lens that can cause “pupil block” glaucoma. The

intraocular pressure may also rise because inflammatory cells

block the trabecular meshwork, and antiglaucoma treatment

may be needed if this occurs. Continued inflammation

may lead to permanent damage of the trabecular

meshwork and secondary glaucoma, cataracts, and oedema of

the macula.

Keratic precipitates

Patients with panuveitis will need systemic investigation and

possibly systemic immunosuppression.

Acute angle closure glaucoma

Acute angle closure glaucoma always should be considered in a

patient over the age of 50 with a painful red eye. The diagnosis

must not be missed or the eye will be damaged permanently.

The mechanism is dealt with in Chapter 9.

History—The attack usually comes on quite quickly,

characteristically in the evening, when the pupil becomes

Hypopyon uveitis

semidilated. There is pain in one eye, which can be extremely

severe and may be accompanied by vomiting. The patient

Features of acute angle closure glaucoma

complains of impaired vision and haloes around lights due to

●

Pain

●

Hazy cornea

oedema of the cornea. The patient may have had similar

●

Haloes around lights

●

Age more than 50

attacks in the past which were relieved by going to sleep (the

●

Impaired vision

●

Eye feels hard

pupil constricts during sleep, so relieving the attack). The

●

Fixed semidilated pupil

●

Unilateral

patient may have needed reading glasses earlier in life. A

patient with acute angle closure glaucoma may be systemically

unwell, with severe headache, nausea, and vomiting, and can be

misdiagnosed as an acute abdominal or neurosurgical

emergency. Acute angle closure glaucoma also may present in

patients immediately postoperatively after general anaesthesia,

and in patients receiving nebulised drugs (salbutamol and

Acute angle closure

ipratropium bromide) for pulmonary disease.

glaucoma. Note the

Examination—The eye is inflamed and tender. The cornea is

corneal oedema (irregular

hazy and the pupil is semidilated and fixed. Vision is impaired

reflected image

of light on cornea) and

according to the state of the cornea. On gentle palpation the

fixed semidilated pupil

eye feels harder than the other eye. The anterior chamber seems

shallower than usual, with the iris being close to the cornea. If

the patient is seen after the resolution of an attack the signs may

Increased resistance

have disappeared, hence the importance of the history.

to flow between iris

and lens.

Management—Urgent referral to hospital is required.

Iris lax

Emergency treatment is needed if the sight of the eye is to be

preserved. If it is not possible to get the patient to hospital

straight away, intravenous acetazolamide 500 mg should be

given, and pilocarpine 4% should be instilled in the eye to

constrict the pupil.

First the pressure must be brought down medically and

Iris is taut

then a hole made in the iris with a laser (iridotomy) or

Build up of aqueous

pushes iris forward,

surgically (iridectomy) to restore normal aqueous flow. The

blocking trabecular

other eye should be treated prophylactically in a similar way. If

meshwork

treatment is delayed, adhesions may form between the iris and

Small pupil

Semidilated pupil

the cornea (peripheral anterior synechiae) or the trabecular

meshwork may be irreversibly damaged necessitating a full

Acute angle closure glaucoma

surgical drainage procedure.

Subconjunctival haemorrhage

History—The patient usually presents with a red eye which is

comfortable and without any visual disturbance. It is usually the

appearance of the eye that has made the patient seek attention.

If there is a history of trauma, or a red eye after hammering or

chiselling, then ocular injury and an intraocular foreign body

must be excluded. Subconjunctival haemorrhages are often

Subconjunctival

seen on the labour ward post partum.

haemorrhage

Red eye

Examination—There is a localised area of subconjunctival

blood that is usually relatively well demarcated. There is no

discharge or conjunctival reaction. Look for skin bruising and

evidence of a blood dyscrasia.

Management—It is worth checking the blood pressure to

exclude hypertension. If there are no other abnormalities the

patient should be reassured and told the redness may take several

weeks to fade. If patients are anticoagulated with warfarin then

the coagulation profile (international normalised ratio, INR)

should be checked. If abnormal bruising of the skin is present

then consider checking the full blood count and platelets.

Inflamed pterygium and pingueculum

Extensive subconjunctival haemorrhage

History—The patient complains of a focal red area or lump in

the interpalpebral area. There may have been a pre-existing

lesion in the area that the patient may have noticed before.

Examination—Pinguecula are degenerative areas on the

conjunctiva found in the 4 and 8 o’clock positions adjacent to,

but not invading, the cornea. These common lesions may be

related to sun and wind exposure. Occasionally they become

inflamed or ulcerated. A pterygium is a non-malignant

fibrovascular growth that encroaches onto the cornea.

Management—If the pingueculum is ulcerated, antibiotics

may be indicated. For a pterygium, surgical excision is

indicated if it is a cosmetic problem, causes irritation, or is

encroaching on the visual axis. Symptomatic relief from the

Pterygium

associated tear-film irregularities are often helped by the use of

topical artificial tear eye drops.

Red eye that does not get better

Red eyes are so common that every doctor will be faced with

a patient whose red eye does not improve with basic

management. It is important to be aware of some of the more

common differential diagnoses.

Bilaterial thyroid eye disease with exophthalmos and

Many of the conditions described below will need a detailed

conjunctival oedema (chemosis)

ophthalmic assessment to make the diagnosis. Consider early

ophthalmic referral when patients present with red eyes and

atypical clinical features or fail to improve with basic

management.

Orbital problems

It is easy to miss someone with early thyroid eye disease and

patients can present with one or both eyes affected. Look for

associated ocular (for example, lid retraction) and systemic

features of thyroid disease. There are several rare but

important orbital causes of chronic red eyes, including carotico-

cavernous fistula, orbital inflammatory disease, and

lymphoproliferative diseases.

Acute dacrocystitis

Eyelid problems

Malpositions of the eyelids such as entropion and ectropion

often cause chronic conjunctival injection. Nasolacrimal

obstruction presents with a watery eye but there can be chronic

ocular injection if the cause is lacrimal canaliculitis or a

lacrimal sac abscess. A periocular lid malignancy such as basal

cell carcinoma or sebaceous (meibomian) gland carcinoma

may rarely present as a unilateral chronic red eye.

Conjunctival problems

If a patient has a history of an infective conjunctivitis that does

not improve, then you should always exclude chlamydial

conjunctivitis, particularly if there are also genitourinary

Chlamydial conjunctivitis

ABC of Eyes

symptoms. Giant papillary conjunctivitis may occur in patients

with ocular allergic disease or in contact lens wearers. If

someone is on long term topical drug therapy (for example,

for glaucoma) then drug hypersensitivity should be considered,

especially if drug instillation causes marked itching or the

eyelids have an eczematous appearance. Other causes of

chronic red eyes include a subtarsal foreign body, dry eyes, and

cicatricial ocular pemphigoid.

Corneal problems

Corneal causes of a chronically red and irritated eye include

Drug hypersensitivity

loose corneal sutures (previous cataract or corneal graft

surgery), herpetic keratitis, exposure keratitis (for example, in

Bell’s palsy), contact lens related keratitis, marginal keratitis

(for example, in patients with blepharitis or rosacea), and

corneal abscess. Fluorescein drops will reveal corneal staining

in patients whose red eye syndrome is caused by a corneal

problem.

Viral infection

Adenoviral keratoconjunctivitis may lead to a red, painful eye

for many weeks and patients should be warned of this. Patients

with refractory adenoviral keratitis may occasionally need

topical steroid therapy. This should only be undertaken with

Subtarsal foreign body

close ophthalmological supervision as it can be hard to wean

patients off steroids.

Scleral problems

Episcleritis and scleritis present with red eyes that do not

respond to topical antibiotic therapy. Think of scleritis in any

patient presenting with marked ocular pain and injection.

Anterior chamber problems

Failure to consider uveitis in a patient with a red eye,

photophobia, and pain can result in delays that make

subsequent management more difficult. Angle closure

Chronic adenovirus

glaucoma has a very characteristic clinical presentation that is

infection

easy to miss.

Refractive errors

Indistinct vision most commonly is caused by errors of

refraction. Doctors do not often have to deal with this problem

because patients usually are prescribed glasses by an

Distance

optometrist. However, if a patient presents complaining of

visual problems, it is extremely important to ask the question:

“Is this patient’s poor vision caused by a refractive error?”

The use of a simple “pinhole” made in a piece of card will

help to determine whether or not there is a refractive error. In

Lens flat

the absence of disease the vision will improve when the pinhole

Light focussed

is used—unless the refractive error is extremely large.

on retina

Eye with no refractive error

Near

In an eye with no refractive error (emmetropia) light rays from

infinity are brought to a focus on the retina by the cornea and

lens when the eye is in a “relaxed” state. The cornea

Out of focus

on retina

contributes about two thirds and the lens about one third to

the eye’s refractive power. Disease affecting the cornea (for

example, keratoconus) may cause severe refractive problems.

Eye with no refractive error. Light rays from distant objects are focused on

The rays of light from closer objects, such as the printed

to the retina without the need for accommodation. Light rays from a close

page, are divergent and have to be brought to a focus on the

object (for example, a book) are focused behind the retina. The eye has to

accommodate to focus these rays

retina by the process of accommodation. The circular ciliary

muscle contracts, allowing the naturally elastic lens to assume a

more globular shape that has a greater converging power.

In young people the lens is very elastic, but with age the

lens gradually hardens and even when the ciliary muscle

contracts the lens no longer becomes globular. Thus from the

age of 40 onwards close work becomes gradually more difficult

(presbyopia). Objects may have to be held further away to

reduce the need for accommodation, which leads to the

complaint “my arms don’t seem to be long enough.” Fine detail

cannot be discerned.

Convex lenses in the form of reading glasses therefore are

needed to converge the light rays from close objects on to the

retina.

Conical cornea (keratoconus) indenting

lower lid on down gaze

All emmetropic people need reading glasses for close work

in later life

No accommodation

Accommodation

People who wear glasses to see clearly in the distance may

Ciliary muscle

relaxes

contracts

find it convenient to change to bifocal lenses in their glasses

when they become presbyopic. In bifocal lenses the reading

lens simply is incorporated into the lower part of the lens.

Therefore, the person does not have to change his or her

glasses to read. However, details at an intermediate distance

such as the prices of items on supermarket shelves are not

Suspensory

clear. A third lens segment can be incorporated between that

ligament taut

ligament lax

for distance above and that for reading below, creating a

trifocal lens. However, many people cannot cope with the

“jump” in magnification inherent in the use of these lenses.

This has led to the introduction of multifocal lenses in which

the lens power increases progressively from top to bottom.

People may also have problems adapting to this type of lens, as

Lens flat

Lens becomes

peripheral vision may be distorted.

globular

Refractive errors do not get worse if a person reads in bad

light or does not wear their glasses. The exceptions are young

children, however, who may need a refractive error corrected to

Accommodation: adjustment of the lens of the eye for

prevent amblyopia.

viewing objects at various distances

ABC of Eyes

Myopic or shortsighted eye

In the myopic eye, light rays from infinity are brought to a

focus in front of the retina because either the eye is too long or

the converging power of the cornea and lens is too great. To

Parallel rays

achieve clear vision the rays of light must be diverged by a

from infinity

concave lens so that light rays are focused on the retina.

No accommodation

Out of focus

on retina

For near vision, light rays are focused on the retina with

little or no accommodation depending on the degree of

myopia and the distance at which the object is held. This is the

reason why shortsighted people can often read without glasses

even late in life, when those without refractive errors need

Concave lens

reading glasses.

diverges rays

A certain type of cataract (nuclear sclerosis) increases the

Focused

on retina

refractive power of the lens, making the eye more myopic.

Patients with these cataracts may say their reading vision has

improved. Patients with an extreme degree of shortsightedness

are more susceptible to retinal detachment, macular

Close object

degeneration, and primary open angle glaucoma.

Little or no

Focused

accommodation

on retina

Myopic or shortsighted eye. Light rays from distant

objects are focused in front of the retina, and the lens

cannot compensate for this. A concave lens has to be

placed in front of the eye to focus the rays on the

retina. Light rays from close objects are focused on the

retina with little or no accommodation. Thus, even

with loss of accommodation, the myopic eye can read

without glasses

Myopic glasses: the face and eyes

seem smaller behind the lenses

Retinal detachment

Macular degeneration with myopic

crescent temporal to disc

Retinal tear (about 0.5 mm)

Nuclear sclerosis

Refractive errors

Hypermetropic or longsighted eye

Typically, the longsighted person needs reading glasses at

about 30 years of age. If a high degree of hypermetropia is

In the hypermetropic eye, light rays from infinity are brought

present, accommodation may not be adequate, and glasses

to a focus behind the retina, either because the eye is too short

may have to be worn for both distant and near vision from

or because the converging power of the cornea and lens is too

an earlier age

weak. Unlike the young shortsighted person, the young

longsighted person can achieve a clear retinal image by

accommodating. Extremely good distance vision can often be

achieved by this “fine tuning”—for example, 6/4 on the

Snellen chart—and this has given rise to the term

“longsighted.” For near vision the longsighted person has to

accommodate even more. This may be possible during the first

two to three decades of life, but the need for reading glasses

arises earlier than in the normal person.

As the ability to accommodate (and thus compensate for

the hypermetropia) fails with advancing years, the longsighted

person may require glasses for both distant and near vision

No accommodation

Out of focus

when none were needed before. This may result in the

complaint of a deterioration in eyesight because the patient has

gone from not needing glasses to needing them for both

distance and near vision.

Longsighted people are more susceptible to closed angle

glaucoma because their smaller eyes are more likely to have

Accommodation

Focused

on retina

shallow anterior chambers and narrow angles.

Astigmatic eye

Astigmatism occurs when the cornea does not have an even

No accommodation

curvature. A good analogy is that of a soccer ball (no

Out of focus

object

astigmatism) and a rugby ball (astigmatism). The curvature of a

normal cornea may be likened to that of the back of a ladle

and that of the astigmatic eye to the back of a spoon. This

uneven curvature results in an uneven focus in different

Considerable

meridians, and the eye cannot compensate by accommodating.

accommodation

Astigmatism can be corrected by a lens that has power in

In focus

only one meridian (a cylinder). Alternatively, an evenly curved

surface may be achieved by fitting a hard contact lens.

Hypermetropic or longsighted eye. Light rays from close

objects are focused behind the retina. The considerable

Astigmatism can be caused by any disease that affects the shape

accommodation required is possible in a young person, but

of the cornea; for example, a meibomian cyst may press hard

reading glasses are needed in later life

enough on the cornea to cause distortion.

Astigmatism can be measured by analysing the image of a

series of concentric rings reflected from the cornea

Contact lenses

Contact lenses have become increasingly popular in recent

years. There are several types, which can be grouped into three

categories.

Reflections of concentric

●

Hard lenses are made of polymethylmethacrylate (plastic

circles showing distortion

by astigmatic cornea

material) and are not permeable to gases or liquids. They

cannot be worn continuously because the cornea becomes

hypoxic and they are the most difficult lenses to get used to.

Because of their rigidity, however, they correct astigmatism

well and are durable. Infection and allergy are less likely with

this type of lens. They are now less commonly prescribed, but

there are still many people who have been using this type of

lens for a long time with no problems.

●

Gas permeable lenses have properties between those of hard

and soft lenses. They allow the passage of oxygen through to

the tear film and cornea, and they are better tolerated than

hard lenses. Being semi-rigid they correct astigmatism better

than soft lenses. They are, however, more prone to the

Gas permable lenses to

accumulation of deposits and are also less durable than hard

correct myopia

ABC of Eyes

lenses. Gas permeable lenses usually are used as daily wear

lenses.

●

Soft lenses have a high water content and are permeable to

both gases and liquids. They are tolerated much better than

hard or gas permeable lenses and they can be worn for much

longer periods. Both infection and allergy, however, are more

common. The lenses are less durable, are more prone to the

accumulation of deposits, and do not correct astigmatism as

well as the harder lenses. Nevertheless, because they are so

well tolerated, they are the most commonly prescribed

lenses.

Soft contact lens fitted after cataract extraction

Certain types of gas permeable and soft lenses can be worn

continuously for up to several months because of their high

oxygen permeability, but the risk of sight threatening

complications is higher than with daily wear lenses.

Disposable lenses are soft lenses that are designed to be

thrown away after a short period of continuous use. They are

popular because no cleaning is required during this period.

However, it is important that the lenses are used as

recommended, or the risk of complications, such as corneal

infection, rise substantially.

Indications for prescribing contact lenses

Personal appearance and the inconvenience of spectacles are

common reasons for prescribing contact lenses. They also may

considerably reduce the optical aberrations that are associated

with the wearing of glasses, particularly those with high power

that are sometimes prescribed for patients who have had

cataracts removed. The brain cannot resolve the large

difference in the size of the retinal images that occurs when

the refractive power of the two eyes differs considerably.

For example, this occurs when a cataract has been

removed from one eye and a spectacle lens has been prescribed

but the other eye is normal. A contact lens brings the image

Normal size

size closer to “normal,” permitting the brain to fuse the two

image with

Image with

intraocular lens

contact lenses

images. If a person is very myopic, the use of contact lenses

Image with

rather than spectacles may increase the image size on the retina

cataract glasses

and improve the visual acuity.

A contact lens can also neutralise irregularities in the

Different sized images with different types of optical correction after

cornea and correct the effects of an irregularly shaped

cataract surgery

cornea (for example, keratoconus or that which occurs after

corneal graft surgery).

Relative contraindications to contact lens wear

Contact lens wear—relative contradictions

Contraindications include a history of atopy, “dry eyes,”

●

Atopy

previous glaucoma filtration surgery, and an inability to handle

●

Dry eyes

or cope with the management of lenses. These are, however,

●

Inability to insert, remove, and care for lenses

relative contraindications; a trial of lenses may be the only way

to determine whether it is feasible for a particular patient to

wear contact lenses.

Complications of wearing contact lenses

The most serious complication of contact lens wear is a corneal

abscess. This is most common in elderly patients who have

worn soft contact lenses for an extended period. Certain

bacterial pathogens such as pneumococci or Pseudomonas

species can cause severe corneal damage and even perforation.

Other pathogens such as acanthamoebae can contaminate

contact lenses or contact lens cases and can produce a chronic

corneal infection with severe pain. Acanthamoebae live in

tap water and it is important to instruct all contact lens wearers

to avoid rinsing their lens cases with tap water. Corneal

Corneal abscess associated with contact lens

wear

abrasions are also fairly common. Chronic lens overuse can

lead to ingrowth of blood vessels into the normally avascular

cornea.

Refractive errors

Any contact lenses wearer with a red eye should have

the contact lens removed and the eye stained with fluorescein

Myopic (shortsighted) eye

Light rays focus in front

of retina

to show up any corneal abrasion or abscess. As fluorescein

stains soft contact lenses, the eye should be washed out with

saline before the lens is replaced. If there is an abrasion or

infection the appropriate treatment should be given, and the

contact lens should not be worn again until the condition has

resolved. The wearing time may have to be built up again,

Radial keratotomy

particularly if hard or gas permeable lenses are worn.

Cuts made in the

Peripheral cornea steepens

Good hygiene is essential for contact lens wearers, to

periphery of the cornea

and central cornea flattens

focusing light on the retina

minimise the risks of infection. Lenses should never be licked

and replaced in the eye. Non-sterile solutions may contain

contaminants such as amoebae, which can lead to intractable

ocular infection.

Refractive surgery

Photorefractive keratectomy

Central cornea

Central cornea flattened

There has been much interest in operations to alter the

reshaped by laser

focusing light on retina

refractive state of the eye, particularly operations to treat

myopia. The technique called radial keratotomy entails making

deep radial incisions in the peripheral cornea, which results in

flattening of the central cornea and refocusing of light rays

nearer the retina. It is only of use in short sight, and possible

disadvantages include weakening of the cornea (particularly if

Laser assisted in situ keratomileusis

the eye subsequently sustains trauma), infection, glare, and

(LASIK)

fluctuation of the refractive state of the eye. If contact lenses

Laser applied to central

Flap repositioned to cover

cornea under a flap

laser treated area

are still required after radial keratotomy has been performed,

they are much more difficult to fit.

Surface-photorefractive keratectomy (S-PRK)

A special (excimer) laser has been used to reprofile the surface

of the cornea. This laser works by vaporising a very thin layer of

the corneal stroma after the corneal epithelium has been

Different types of

debrided (photoablation), which reshapes the front surface of

refractive surgery to

the cornea, changing its focusing power. This technique,

correct myopia

known as surface-photorefractive keratectomy (S-PRK), is safer

than radial keratotomy, as it does not involve deep cuts into the

eye. Side effects include:

●

pain for a few days after the laser treatment

●

haze-regression reactions (a period when the vision becomes

Edge of the

hazy, along with a tendency for the refraction to regress back

debrided

corneal

towards myopia again)

epithelium

●

overcorrection with a hypermetropic shift (often poorly

tolerated)

●

corneal opacification caused by scarring of the treated zone,

which may result in a reduction of best corrected visual acuity

(usually transient) and glare.

Edge of the

Predictability of the final refractive result is poorer if the

treated area

patient is very shortsighted. (This is particularly the case if the

patient has more than 6 dioptres of myopia.)

Surface-photorefractive keratectomy—the corneal

epithelium has been removed and the laser has

Laser assisted in situ keratomileusis (LASIK)

remodelled a precise area of the corneal stroma

More recently, a technique called laser assisted in situ

keratomileusis (LASIK) has been introduced. This entails

cutting a superficial hinged flap in the cornea (about 160 to

200 m thick) with an automated microkeratome, carrying out

excimer laser reshaping of the underlying corneal stroma, and

then replacing the flap. Advantages of the technique over

surface laser treatment include more rapid stabilisation of

vision, reduced corneal scarring (with a definite reduction in

haze-regression reactions), and much better correction of

higher degrees of myopia. Accuracy of LASIK is optimal up to

Radial keratotomy—the

6.00 dioptre sphere (DS), good up to

8.00 DS, and starts to

cornea is flattened by

multiple radial incisions

become increasingly less accurate over

10.00 DS.

reducing the myopia

ABC of Eyes

Disadvantages include complications associated with the

technical difficulties of cutting and replacing the thin surface

flap, which occur in 1-5% of patients.

A recent modification of LASIK is LASEK, in which an

epithelial flap is raised prior to stromal ablation and then

replaced. Other methods of altering the refractive status of the

eye include corneal intrastromal rings, phakic intraocular

lenses (intraocular lenses when the natural lens remains), and

small incision clear lensectomy. Laser techniques can also be

Grey scar in the

used to correct astigmatism and hypermetropia, although these

corneal area

are used much less commonly.

treated by the

laser

Possible complications of surgery

Patients who are contemplating any type of refractive surgery

should be fully informed of the risks by the operating surgeon

and given time to evaluate the advantages and disadvantages

before undergoing a procedure that may cause irreversible

change. This is especially important as many patients will have

pre-operative best corrected visual acuities of 6/6 or better

(although they will need glasses or contact lenses to achieve

this vision). It should be emphasised that the risk of

complications is low, but complications are potentially

devastating to vision. Complications that may occur include:

●

infection—corneal infection is a rare problem associated with

all refractive procedures and can substantially reduce vision.

●

corneal perforation—this may very rarely occur in association

with technical problems with the microkeratome in LASIK.

●

corneal flap problems—there may occasionally be problems in

cutting or replacing the corneal flap in LASIK. Flap

irregularites, subflap foreign bodies, unstable flaps, and flap

Microkeratome

melts all have been reported. Epithelial ingrowth under the

corneal flap is a rare complication.

●

corneal ectasia—photoablative procedures all reduce the

corneal thickness. If too much corneal stroma is removed

then the cornea can progressively thin and become ectatic.

●

regression of refractive outcome—in some patients the cornea

undergoes a period of remodelling after refractive surgery,

with a tendency to drift back towards the original refractive

status.

●

refractive under- or overcorrection—this occurs where the

anticipated refractive correction does not occur.

Overcorrection of myopia to produce hypermetropia often is

tolerated poorly by the patient.

●

corneal stromal scarring—postoperative corneal stromal scarring

produces corneal haze, which produces optical aberrations

(reduced best acuity, glare, reduced contrast, and problems

with night vision).

●

optic neuropathy—very rarely, patients have been reported to

Microkeratome

on eye

lose vision as a result of optic nerve damage after refractive

procedures involving cutting a corneal flap. Optic nerve

damage may be related to the transient but very high rise in

intraocular pressure that occurs when the microkeratome is

applied to the eye.

●

retinal detachment—this serious complication may possibly be

caused by tractional forces exerted on the eye when the

microkeratome is used during refractive surgery.

Eyelid, orbital, and lacrimal disorders

Lumps in the lid

Importance of lumps in the eyelid

●

May need disfiguring operations if left

The most common lump found in the eyelid is a chalazion, but

●

May be life threatening

the accurate diagnosis of a lid lump is important because the

●

May be the cause of visual disturbance

lump may:

●

May cause blindness in children

●

May indicate systemic disease

●

necessitate a disfiguring operation if not treated early—basal cell

carcinoma

●

be life threatening—a deeply invading basal cell carcinoma

●

be the cause of visual disturbance—a chalazion pressing on the

cornea and causing astigmatism

●

indicate systemic disease—xanthelasmas in a patient with

hyperlipidaemia

●

cause amblyopia—if it obstructs vision in a young child.

Chalazion

A chalazion (meibomian cyst) is a granuloma of the lipid-

secreting meibomian glands that lie in the lid. It is probably the

result of a blocked duct, with local reaction to the

accumulation of lipid.

Chalazion

The patient may initially complain of a lump in the lid that

is hard and inflamed. This settles and the patient is left with a

discrete lump in the lid that may cause astigmatism and

consequent blurring of vision. Clinically there is a hard lump in

the lid, which is clearly visible when the lid is everted.

Many chalazia settle on conservative treatment. This

comprises warm compresses (with a towel soaked in warm

water) and the application of chloramphenicol ointment.

However if the chalazion is uncomfortable, excessively large,

persistent, or disturbs vision, it can be incised and curetted

under local anaesthesia from the inner conjunctival side of the

eyelid.

Recurrent chalazia may indicate an underlying problem

Incised chalazion

such as blepharitis, a skin disorder such as acne rosacea, or

even, though very rarely, a malignant tumour of the meibomian

glands.

Stye

A stye and chalazion are often confused. A stye is an infection

of a lash follicle, which causes a red, tender swelling at the lid

margin. Unlike a chalazion, a stye may have a “head” of pus at

the lid margin. It should be treated with warm compresses to

help it to discharge, and chloramphenicol ointment should be

used.

Marginal cysts

Marginal cysts may develop from the lipid and sweat secreting

Stye

glands around the margins of the eyelids. They are dome shaped

with no inflammation. The cysts of the sweat glands are filled

with clear fluid (cyst of Moll) and the cysts of the lipid secreting

glands are filled with yellowish contents (cyst of Zeiss).

No treatment is indicated for marginal cysts that cause no

problems. If they are a cosmetic blemish they can be removed

under local anaesthesia.

Papilloma

Papillomas are often pedunculated and multilobular. They are

common and may be caused by viruses. They should be

removed if they are large and the diagnosis is uncertain, or if

Cyst of sweat secreting

they are disfiguring.

gland (cyst of Moll)

ABC of Eyes

Xanthelasma

Xanthelasmas may be an incidental finding, or the patient may

complain of yellow plaques on the nasal sides of the eyelids;

these contain lipid. Associated hyperlipidaemia must be

excluded and the lesions may be removed under local

anaesthesia if they are a cosmetic problem.

Basal cell carcinoma

Basal cell carcinoma (rodent ulcer) is the most common

malignant tumour of the eyelid. It occurs mainly in the lower

Xanthelasmas and corneal arcus in a young

lid, which is particularly exposed to sunlight. The tumour does

patient

not metastasise but may be life threatening if allowed to

infiltrate locally. Tumours in the medial canthal region may

infiltrate the orbit extensively if they are not detected and

dealt with. If the tumour is large when the patient is referred,

an extensive and often disfiguring operation may be necessary.

The classical basal cell carcinoma has a pearly rounded

edge with a necrotic centre, but it may be difficult to

diagnose if it presents as a diffuse indurated lesion. It is

particularly easy to miss the invasive form that occurs in

a skin crease, which may be invading deeply with few

cutaneous signs.

The patient should be referred urgently if there is any

suspicion of a basal cell carcinoma. It usually is excised under

Basal cell carcinoma. Recently enlarging,

local anaesthesia, unless complicated plastic reconstructive

with some bleeding

surgery is required. Radiotherapy may also be used as palliative

therapy in periorbital disease. Patients with basal cell carcinomas

around the eye will often have other facial skin tumours.

Squamous cell carcinomas are rare in the periorbital region, but

are much more locally invasive and may also metastasise.

Inflammatory disease of the eyelid

Blepharitis

Blepharitis is a common condition but is often not diagnosed.

It is a chronic disease; the patient complains of persistently sore

eyes. The symptoms may be intermittent and include a gritty

sensation and sore eyelids. The patient may present with a

Basal cell carcinoma with classic pearly rolled

edge

chalazion or stye, which are much more common in patients

with blepharitis, and these may be recurrent. Physical signs

include inflamed lid margins, blocked meibomian gland

orifices, and crusts round the lid margins. The conjunctiva may

be inflamed, and punctate staining of the cornea may be visible

on staining with fluorescein. Associated skin diseases include

rosacea, eczema, and psoriasis. The aims of treatment are to:

●

keep the lids clean—the crusts and coagulated lipid should be

gently cleaned with a cotton wool bud dipped in warm water.

This can be combined with baby shampoo to help remove

lipid

Blepharitis. Left: inflamed lid margin. Right: crust around lid margin

●

treat infection—antibiotic ointment should be smeared on the

lid margin to help kill the staphylococci in the lid that may

be aggravating the condition. This may be done for several

months

●

replace tears—the tear film in patients with blepharitis is

abnormal, and artificial tears may provide considerable relief

of symptoms

●

treat sebaceous gland dysfunction—in severe cases, or those

associated with sebaceous gland dysfunction, such as rosacea,

oral tetracycline may be invaluable. Indications for referral

are poor response to treatment and corneal disease.

Acute inflammation of the eyelid

It is important to achieve a diagnosis in a patient with an

acutely inflamed eyelid, as some conditions may be blinding—

for example, orbital cellulitis (see page 25).

Rosacea with associated blepharitis

Eyelid, orbital, and lacrimal disorders

Chalazion and stye

Routine treatment should be given for these conditions.

If infection is spreading, prescribe systemic antibiotics.

Spread of local infection

Infection may have spread from a local lesion such as a

“squeezed” comedo. Again, if there is spread of infection,

Chalazion with associated

systemic antibiotics are needed.

inflammation of the lower

eyelid

Acute dacryocystitis

The site of the inflammation is medial, over the lacrimal sac.

There may be a history of previous watering of the eye as a

result of a blocked lacrimal system that has since become

infected. Treatment is with topical chloramphenicol and

systemic antibiotics until the infection resolves. Recurrent

attacks of dacryocystitis or symptomatic watering of the eye are

indications for operation.

Allergy

There may be a history of contact with an allergen, including

animals, plants, chemicals, or cosmetics. Itching is an indicator

Inflammation of upper

of allergy. Treatment may include weak topical steroid

eyelid after expression

ointment (hydrocortisone 1%) applied to the eyelid for a short

of blackhead

period. The use of steroid ointments in the periorbital area

should be monitored very closely, because of the potentially

serious complications of even short term usage (glaucoma,

cataract, herpes simplex keratitis, and atrophy of the skin).

Herpes simplex

This may present as a vesicular rash on the skin of the eyelid.

There may be associated areas of vesicular eruption on the face.

An “experienced” patient may be able to discern the prodromal

tingling sensation. Early application of aciclovir cream will

shorten the length and severity of the episode. Associated ocular

herpetic disease should be considered if the eye is red, and the

patient should then be referred immediately.

Dacryocystitis with

associated lid inflammation

Herpes zoster ophthalmicus (shingles)

This presents as a vesicular rash over the distribution of the

ophthalmic division of the fifth cranial nerve. There may be

associated pain and the patient usually feels unwell.

The eye is often affected, particularly if the side of the

nose is affected (which is innervated by a branch of the

nasociliary nerve that also innervates the eye). Common

ocular problems include conjunctivitis, keratitis, and uveitis.

The eye is often shut because of oedema of the eyelid, but an

attempt should be made to inspect the globe. If the eye is red

or if there is visual disturbance the patient should be referred

straight away. The ocular complications of herpes zoster may

occur after the rash has resolved and even several months

Herpes simplex with

after primary infection, so the eye should be examined at

associated conjunctivitis

each visit. Serious ophthalmic complications include

glaucoma, cataract, uveitis, choroiditis, retinitis, and

oculomotor palsies.

Treatment includes application of a wetting cream to the

skin after crusting to prevent painful and disfiguring scars. If

the eye is affected, topical antibiotics may prevent secondary

infection, and aciclovir ointment is used. Oral antiviral therapy

(for example, aciclovir) given early in the course of the disease

may reduce the incidence of long term sequelae such as

postherpetic neuralgia.

Proptosis and enophthalmos

Globe protrusion (proptosis) and sunken globe

(enophthalmos) result in an asymmetrical position of the

Herpes zoster ophthalmicus

globes, which can often be best appreciated by standing behind

with swollen eyelids

ABC of Eyes

the patient and looking from above their head (comparing the

Orbital cellulitis can cause blindness if not treated

position of the eyes relative to the brows). The degree of

immediately—particularly in children

proptosis or enophthalmos can be quantified by using an

exophthalmometer. All patients with proptosis or

enophthalmos need full ophthalmic and systemic investigation.

There are many causes of proptosis and enophthalmos: some of

the more common and important diseases are listed below.

Causes of proptosis

Orbital cellulitis—This is a potentially life threatening and

blinding condition and must not be missed. Orbital cellulitis

usually results from the spread of infection from adjacent

Orbital cellulitis:

paranasal sinuses. It is particularly important in children, in

swollen eyelids,

whom blindness can ensue within hours, because the orbital

conjunctival

swelling,

walls are so thin. The patient usually presents with unilateral

displaced eyeball,

swollen eyelids that may or may not be red. Features to look

and restricted eye

for include:

movements

●

the patient is systemically unwell and febrile

●

there is tenderness over the sinuses

●

there is proptosis, chemosis, reduced vision, and restriction

of eye movements.

The possibility of orbital cellulitis should always be kept in

mind, especially in children, and patients should be referred

immediately without any delay.

Orbital inflammatory disease—Non-specific orbital

inflammatory disease can occur as an isolated finding or in

association with a number of systemic vasculitides, including

Wegener’s granulomatosis.

Thyroid eye disease—See Chapter 12.

Orbital lymphoma—Deposits of lymphoma in the orbit need

confirmation by orbital biopsy and should alert the clinician to

the need for a full systemic work up for lymphoma elsewhere.

Lacrimal gland tumour—These tumours in the upper outer

part of the orbit displace the globe inferiorly and medially.

Orbital invasion from paranasal sinus infection or tumour—Look

Computed tomogram of head/orbits showing enlarged extraocular muscles

for features of nasal or sinus disease in the history and examine

and optic nerve compression in thyroid eye disease

the nose, oropharynx, and lymph nodes.

Causes of enophthalmos

Blowout orbital fracture—See Chapter 5.

Microphthalmos—If one eye is smaller than the other due to

developmental problems in embryogenesis, then the eye will

appear enophthalmic. Microphthalmic eyes often have other

problems including cataract and refractive errors.

Cicatrising metastatic breast carcinoma—This rare form of

progressive enophthalmos is associated with very poor

prognosis for survival.

Malpositions of the eyelids and

eyelashes

Malpositions of the eyelids and eyelashes are common and give

rise to various symptoms, including irritation of the eye by lashes

rubbing on it (entropion and ingrowing eyelashes) and watering

of the eye caused by malposition of the punctum (ectropion).

Blowout fracture of the orbit with fluid in the maxillary sinus

The eyelids are folds of skin with fibrous plates in both the

upper and lower lids, and the circular muscle (orbicularis)

controls the closing of the eye. Any change in the muscles or

supporting tissues may result in malposition of the lids.

Main symptoms of lid and lash malposition

Entropion

●

Irritation of the eye by lashes rubbing on it (entropion)

Entropion is common, particularly in elderly patients with some

●

Watering of the eye caused by malposition of the punctum

spasm of the eyelids. The patient may present complaining of

(ectropion)

irritation caused by eyelashes rubbing on the cornea. This may

Eyelid, orbital, and lacrimal disorders

be immediately apparent on examination but may be

intermittent, in which case the lid may be in the normal

position. The clue is that the eyelashes of the lower lid are

pushed to the side by the regular inturning. The entropion can

be brought on by asking the patient to close their eyes tightly,

and then open them.

The great danger of entropion is ulceration and scarring of

the cornea by the abrading eyelashes. The cornea should be

examined by staining with fluorescein.

Temporary treatment of entropion consists of taping

Entropion: inturning eyelashes may scratch

down the lower lid and applying chloramphenicol ointment.

and damage the cornea

An operation under local anaesthesia is required to correct

the entropion permanently. Scarring of the cornea,

associated with entropion of the upper eyelid resulting from

trachoma, is one of the most common causes of blindness

worldwide.

Trichiasis

Sometimes the lid may be in a normal position, but aberrant

eyelashes may grow inwards. Trichiasis is more common in the

presence of diseases of the eyelid such as blepharitis or

Temporary treatment of entropion

trachoma. The eyelashes can be seen on examination,

especially with magnification. They can be pulled out, but they

frequently regrow.

The application of chloramphenicol ointment helps to

prevent corneal damage, and electrolysis of the hair roots

or cryotherapy may be necessary to stop the lashes

regrowing.

Ectropion

The initial complaint may be of a watery eye. The tears

drain mainly via the lower punctum at the medial end of

the lower lid. If the eyelid is not properly apposed to the eye,

tears cannot flow into the punctum and the result is a

Trichiasis

watery eye.

The patient may also complain about the unsightly

appearance of the ectropion. The most common reason for

ectropion is laxity of tissues of the lid as a result of ageing, but

it also occurs if the muscles are weak, as in the case of a facial

nerve palsy. Scarring of the skin of the eyelid may also pull the

lid margin down.

Ectropion can be rectified by an operation under local

anaesthesia. Use of a simple lubricating ointment before the

operation will help to protect the eye and prevent drying of the

exposed conjunctiva.

Ectropion with resulting epiphora

Ptosis

Ptosis or drooping of the eyelid may:

Ptosis may occasionally:

●

indicate a life threatening condition—such as a third nerve palsy

●

Indicate a life threatening disease

secondary to aneurysm or a Horner’s syndrome secondary to

●

Indicate a systemic disease

●

Cause amblyopia in children

carcinoma of the lung

●

indicate a disease that needs systemic treatment—such as

myasthenia gravis

●

cause irreversible amblyopia in a child as a result of the lid

obstructing vision. If there is any question of a ptosis

obstructing vision in a child, he or she should be referred

urgently.

●

be easily treated by a simple operation—as in senile ptosis.

The patient will usually complain of a drooping eyelid. The

upper eyelid is raised by the levator muscle, which is controlled

by the third nerve. There is also Müller’s muscle, which is

controlled by the sympathetic nervous system. These muscles

are attached to the fibrous plate in the eyelid and other lid

structures. The ptosis can occur because of tissue defects, as

Ptosis caused by lid haemangioma; exclude amblyopia

described below.

in a child

ABC of Eyes

Lid tissues

With ageing, the tissues of the eyelid become lax and the

connections loosen, resulting in ptosis; this is common in the

elderly. The eye movements and pupils should be normal.

A pseudoptosis may occur when the skin of the upper lid

sags and droops down over the lid margin. Both these

conditions are amenable to relatively simple operations

under local anaesthesia.

Muscle tissue

It is important not to miss a general muscular disorder such as

myasthenia gravis or dystrophia myotonica in a patient who

presents with ptosis. Any diplopia, worsening symptoms

throughout the day, and other muscular symptoms should lead

Left ptosis caused by pupil sparing third nerve palsy:

note the divergent eye

one to suspect myasthenia. The patient’s facies and a “clinging”

handshake may give clues to the diagnosis of dystrophia

myotonica.

Nerve supply

A third nerve palsy may present as a ptosis. This, together with

an abducted eye and dilated pupil, indicates the diagnosis. The

patient should be referred urgently, as causes of third nerve

palsy include a compressive lesion of the third nerve such as an

aneurysm. Diabetes should be excluded.

Horner’s syndrome resulting from damage to the sympathetic chain

The pupil will be small but reactive, and sweating over the

affected side of the face may be reduced. The eye movements

should be normal. Causes of Horner’s syndrome include

lesions of the brain stem and spinal cord, dissection of the

carotid artery and apical lung tumours, so the patient should

Clinical thyroid eye disease

be referred.

Lid retraction

Lid retraction and associated lid lag are features of thyroid eye

disease. These signs can occur in patients who are

hyperthyroid, euthyroid, or hypothyroid.

Blepharospasm

In essential blepharospasm there is episodic bilateral

involuntary spasm of the orbicularis oculi muscles, which leads

to unwanted forced closure of both eyes. Treatment options for

this disabling condition include muscle relaxants, botulinum

toxin injection, and surgical stripping of some of the

orbicularis fibres.

Spread by

Secreted by

blinking

Lacrimal system

tear gland

Watering eye

Into canaliculii

at puncta

Tears are produced by the lacrimal glands that lie in the

upper lateral aspect of the orbits. They flow down across the

eye along the lid margins and are spread across the eye by

blinking. They then flow through the upper and lower puncta

Flow along

to the lacrimal sac and down the nasolacrimal duct into the

eyelid margin

nose.

Although rare, it is important to remember that children

with congenital glaucoma may present with watery eyes. A

watering eye may occur for several reasons.

Nasolacrimal duct

Excessive production of tears

This is rare, but can occur paradoxically in a patient with “dry

eyes.” Basal secretion of tears is inadequate and this results in

Normal tear flow

drying of the eye. This gives rise to a reactive secretion of tears

that causes epiphora. The patient may have a history of

intermittent discomfort followed by watering of the eye.

Eyelid, orbital, and lacrimal disorders

Punctal malposition secondary to lid malposition

The punctum must be well apposed to the eye to drain tears.

Even mild ectropion can result in pooling of tears and

overflow. Careful examination of the lid will usually show any

malposition, which may be remedied by performing a minor

operation.

Punctal stenosis

The punctum may close up and this will result in watering.

If this is the case, the punctum cannot be seen easily on

Watering eye caused by punctal ectropion

examination with a magnifying loupe. It can be surgically

dilated or opened by a minor operation under local

anaesthesia.

Blockage of the lacrimal sac or nasolacrimal duct

If the nasolacrimal duct is blocked and cannot be freed by

syringing, an operation may be required. A common operation

to bypass the obstruction is a dacryocystorhinostomy (DCR), in

Blockage bypassed by

making new channel

which a hole is made into the nose from the lacrimal sac.

into the nose

Sometimes plastic tubes are left in for several months to create

a fistula. This major operation usually is performed under

general anaesthesia.

A recent addition to the range of procedures for the

surgical treatment of watery eyes is endoscopic DCR, in which

the operation is performed through the nasal cavity. Good

Blockage

results are reported for this procedure, although external DCR

still has the higher success rate.

In children the lacrimal drainage system may not be

patent, particularly in the first few years of life. The child

will present with a watering eye or sometimes with recurrent

conjunctivitis. Treatment is usually with chloramphenicol

eye drops for episodes of conjunctivitis, and the parents

Dacryocystorhinostomy

should massage the lacrimal sac daily to encourage flow. Most

cases in childhood will resolve spontaneously. If the

watering persists, the child may have to have the sac and duct

syringed and probed under general anaesthesia. This

procedure is generally best done between 12 and 24 months

of age. If the blockage persists, a dacryocystorhinostomy may

be performed when the child is older, but this is not often

necessary.

Dry eye

Dry eye is common in the elderly, in whom tear secretion is

reduced. The patient usually presents complaining of a chronic

gritty sensation in the eye, which is not particularly red.

Sjögren’s syndrome is an autoimmune disease, with features of

dry eyes and dry mouth, which can occur with certain

Blocked left nasolacrimal system in a child

with recurrent discharge

connective tissue diseases such as rheumatoid arthritis. Drugs

such as diuretics and agents with anticholinergic action (for

example, certain drugs used in the treatment of depression,

Parkinson’s disease, and bladder instability) may also

exacerbate the symptoms of dry eye.

Staining of the cornea may be apparent with fluorescein

and rose bengal eye drops. (If rose bengal eye drops are used

the eyes must be washed out very thoroughly, as these drops are

a potent irritant.) A Schirmer’s test can be carried out. A strip

of filter paper is folded into the fornix and the advancing edge

of tears is measured.

Treatment includes:

●

artificial tear drops, which may be used as frequently as

necessary (it may be necessary to use preservative free

artificial tears in severe cases)

Dry eye in rheumatoid arthritis, stained with

●

simple ointment, which helps to give prolonged lubrication,

rose bengal drops, which stain damaged

particularly at night when tear secretion is minimal

epithelium

Injuries to the eye

An injury to the eye or its surrounding tissues is the most

common cause for attendance at an eye hospital emergency

Abnormal eye movements:

Foreign body

always refer

Distorted pupil:

department.

beware penetrating injury

Basal tear

Deep laceration of orbit:

of iris always refer

beware intraorbital and intraocular

penetration and retained

History

foreign bodies

The history of how the injury was sustained is crucial, as it gives

clues as to what to look for during the examination. If there is

a history of any high velocity injury (particularly a hammer and

chisel injury) or if glass was involved in the injury, then a

penetrating injury must be strongly suspected and excluded.

If there has been a forceful blunt injury (such as a punch),

signs of a “blowout” fracture should be sought. The

circumstances of the injury must be elicited and carefully

recorded, as these may have important medicolegal

implications. It may not be possible to get an accurate and

reliable history from children if an injury is not witnessed by an

Hyphaema:

adult. Such injuries should be treated with a high index of

Marginal laceration:

always refer

Subconjunctional

always refer

haemorrhage: if it tracks

suspicion, as a penetrating eye injury may be present.

Epithelial loss—may

be missed

posteriorly beware orbital

without fluorescein

fracture

Examination

The injured eye

A good examination is vital if there is a history of eye injury.

Specific signs must be looked for or they will be missed. It is

vital to test the visual acuity, both to establish a baseline value

Common types of eye injury

and to alert the examiner to the possibility of further problems.

● Corneal abrasions

However, an acuity of 6/6 does not necessarily exclude serious

● Foreign bodies

problems—even a penetrating injury. The visual acuity may also

● Radiation damage

have considerable medicolegal implications. Local anaesthetic

● Chemical damage

may need to be used to obtain a good view, and fluorescein

● Blunt injuries with hyphaema

must be used to ensure no abrasions are missed.

● Penetrating injuries

Corneal abrasions

Corneal abrasions are the most common result of blunt injury.

They may follow injuries with foreign bodies, fingernails, or

twigs. Abrasions will be missed if fluorescein is not instilled.

The aims of treatment are to ensure healing of the defect,

prevent infection, and relieve pain.

Small abrasions can be treated with chloramphenicol

ointment twice a day or eye drops four times a day until the eye

has healed and symptoms are gone. Ointment blurs the vision

more but provides longer lasting lubrication compared with eye

drops. This will help prevent infection, lubricate the eye

surface, and reduce discomfort.

For larger or more uncomfortable abrasions a double eye pad

can be used with chloramphenicol ointment for a day or so until

symptoms improve. If the eye becomes uncomfortable with the

pad, it can be removed and the eye treated as per a small

Corneal abrasion stained with fluorescein and

illuminated with white light

abrasion. The pad must be firm enough to keep the eyelid shut.

Ointment or drops can then continue. If there is significant pain

cycloplegic eye drops (cyclopentolate 1% or homatropine 2%)

may help, although this will further blur the vision. Oral analgesia

such as paracetamol or stronger non-steroidal anti-inflammatory

drugs can also be used. Patients should be told to seek futher

ophthalmological help if the eye continues to be painful, vision is

blurred, or the eye develops a purulent discharge.

Recurrent abrasions—Occasionally the corneal epithelium

may repeatedly break down where there has been a previous

injury or there is an inherently weak adhesion between

the epithelial cells and the basement membrane. These

Corneal abrasion stained with fluorescein and

recurrences usually occur at night when there is little secretion

illuminated with blue light

ABC of Eyes

of tears and the epithelium may be torn off. Treatment is long

term and entails drops during the day and ointment at night to

lubricate the eye. Occasionally, a surgical procedure (such as

epithelial debridement or corneal stromal puncture) may be

carried out to enhance the adhesion between the epithelium

and the underlying basement membrane.

Foreign bodies

It is important to identify and remove conjunctival and corneal

foreign bodies. A patient may not recall a foreign body having

entered the eye, so it is essential to be on the lookout for a

foreign body if a patient has an uncomfortable red eye. It may

be necessary to use local anaesthetic both to examine the eye

and to remove the foreign body. Although patients often

request them, local anaesthetics should never be given to

patients to use themselves, because they impede healing and

further injury may occur to an anaesthetised eye.

Small loose conjunctival foreign bodies can be removed

with the edge of a tissue or a cotton wool bud or they can be

washed out with water. The upper lid must be everted to

exclude a subtarsal foreign body, particularly if there are

corneal scratches or a continuing feeling that a foreign body is

present. However, this should not be done if a penetrating

injury is suspected. Corneal foreign bodies are often more

difficult to remove if they are metallic, because they are often

“rusted on.” They must be removed as they will prevent healing

Removal of a foreign body

and rust may permanently stain the cornea. A cotton wool bud

from the eye

or the edge of a piece of cardboard can be used. If this does

not work, a needle tip (or special rotary drill) can be used, but

great care must be taken when using these as the eye may easily

be damaged. If there is any doubt, these patients should be

referred to an ophthalmologist. When the foreign body has

been removed any remaining epithelial defect can be treated as

an abrasion.

Lower lid gently pulled

down to show a conjunctival

Removal of a foreign body

foreign body. The cornea

has also been perforated

●

Use local anaesthetic

●

If the foreign body is loose, irrigate the eye

●

If the foreign body is adherent, use a cotton wool bud or the

edge of a piece of cardboard

Radiation damage

The most common form of radiation damage occurs when

welding has been carried out without adequate shielding of the

eye. The corneal epithelium is damaged by the ultraviolet rays

Subtarsal foreign body

and the patient typically presents with painful, weeping eyes

some hours after welding. (This condition is commonly known

as “arc eye.”)

Radiation damage can also occur after exposure to large

amounts of reflected sunlight (for example, “snow blindness”)

or after ultraviolet light exposure in tanning machines.

Treatment is as for a corneal abrasion.

Cornea after welding damage,

stained with fluorescein and

illuminated with blue light

Chemical damage

All chemical eye injuries are potentially blinding injuries. If

chemicals are splashed into the eye, the eye and the

conjunctival sacs (fornices) should be washed out immediately

with copious amounts of water. Acute management should

consist of the three “Is”: Irrigate, Irrigate, Irrigate. Alkalis are

particularly damaging, and any loose bits such as lime should

be removed from the conjunctival sac, with the aid of local

Chemical injury to the eye

Injuries to the eye

anaesthetic if necessary. The patient should then be referred

Dealing with chemical damage to the eye

immediately to an ophthalmic department. If there is any

●

Immediately wash out eye with water

doubt, irrigation should be continued for as long as possible

●

Remove loose particles

with several litres of fluid.

●

Refer patient to ophthalmic department

●

Beware alkalis

Blunt injuries

If a large object (such as a football) hits the eye most of the

impact is usually taken by the orbital margin. If a smaller object

(such as a squash ball) hits the area the eye itself may take most

of the impact.

Haemorrhage may occur and a collection of blood may be

plainly visible in the anterior chamber of the eye (hyphaema).

Patients who sustain such injuries need to be reviewed at an eye

unit as the pressure in the eye may rise, and further

haemorrhages may require surgical intervention. Haemorrhage

may also occur into the vitreous or in the retina, and this may

be accompanied by a retinal detachment. All patients with

Large object :

Small object :

visual impairment after blunt injury should be seen in an

impacts on orbital

eye and orbit take

margin

impact

ophthalmic department.

The iris may also be damaged and the pupil may react

poorly to light. This is particularly important in a patient with

an associated head injury, as this may be interpreted as (or

mask) the dilated pupil that is suggestive of an acute extradural

Dislocated

lens

haematoma. The lens may be damaged or dislocated and a

Vitreous

cataract may develop. Damage to the drainage angle of the eye

haemorrhage

(which cannot be seen without a mirror contact lens and a slit

lamp microscope) increases the chances of glaucoma

developing in later life.

Damage to angle

If the force of impact is transmitted to the orbit, an orbital

(risk of subsequent

fracture may occur (usually in the floor, which is thin and has

glaucoma)

Retinal tear

little support). Clues to the presence of an inferior “blowout”

fracture include diplopia, a recessed eye, defective eye

Complications of blunt trauma to the eye

movements (especially vertical), an ipsilateral nose bleed, and

diminished sensation over the distribution of the infraorbital

nerve. These patients need to be seen in an ophthalmic

department for assessment and treatment of eye damage, and a

maxillofacial department for repair of the orbital floor.

Hyphaema

Peripheral

Enlarged pupil:

tear in iris

damaged sphincter

Signs of damage to the eye itself

Hyphaema

Restricted vertical

movement

Subconjunctival

haemorrhage

Swollen lid

Loss of sensation

Ipsilateral nose bleed

Radiograph showing blowout fracture of the left orbit with fluid in the

Signs of a left orbital blowout fracture (patient looking upwards)

maxillary sinus

ABC of Eyes

Penetrating injuries and eyelid

Penetrating eye injuries—beware:

lacerations

●

Hammer and chisel

●

Glass

Lacerations of the eyelids need specialist attention if:

●

Knives

●

Thorns

●

the lid margins have been torn—these must be sewn together

●

Darts

accurately

●

Pencils

●

the lacrimal ducts have been damaged—the laceration may

involve the medial ends of the eyelids and it is likely that the

lacrimal canaliculi will have been damaged, and these may

need to be reapposed under the operating microscope

●

there is any suspicion of a foreign body or penetrating eyelid injury—

objects may easily penetrate the orbit and even the cranial

cavity through the orbit.

Penetrating injuries of the eye can be missed because

they may seal themselves, and the signs of abnormality are

subtle. Any history of a high velocity injury (particularly a

hammer and chisel injury) should lead one strongly to suspect

a penetrating injury. In that case, the eye should be examined

very gently and no pressure should be brought to bear on the

globe. It is possible to cause prolapse of intraocular contents

and irreversible damage if the eye and orbit are not examined

with great care.

Lacerated eyelid

Signs to look for include a distorted pupil, cataract,

prolapsed black uveal tissue on the ocular surface, and vitreous

haemorrhage. The pupil should be dilated (if there is no head

injury) and a thorough search made for an intraocular foreign

body. If there is a suspicion of an intraocular or orbital foreign

body then orbital x ray photographs, with the eye in up and

down gaze, should be taken.

If the eye is clearly perforated it should be protected from

any pressure by placing a shield over the eye, and the patient

should be sent immediately to the nearest eye department.

Sympathetic ophthalmia, in which chronic inflammation

develops in the normal fellow eye, is a potentially serious

complication of any severe penetrating eye injury. The risk of

this increases if a penetrating eye injury is left untreated. All

penetrating eye injuries should receive immediate specialist

ophthalmic management without delay.

Penetrating eye injury

Acute visual disturbance

Acute disturbance of vision in a non-inflamed eye demands an

accurate history, as the patient may have only just noticed a

longstanding visual defect. Acute visual disturbance of

unknown cause requires urgent referral.

History and examination of a

patient with acute visual

disturbance

Symptoms and signs

History

In many cases the diagnosis can be made from the history.

●

Floaters

Symptoms of floaters or flashing lights suggest a vitreous

●

Field loss

●

Zigzag lines

detachment, a vitreous haemorrhage, or a retinal detachment.

●

Flashing lights

Horizontal field loss usually indicates a retinal vascular

●

Headache

problem, whereas a vertical defect suggests a neuro-ophthalmic

●

Pain on moving eye

abnormality at or posterior to the optic chiasm. If there is

Examination

central field loss (“I can’t see things in the centre of my vision”

●

Acuity

or “I can’t see people’s faces”) there may be a disorder at the

●

Pupil reactions

macula or within the optic nerve. Associated systemic

●

Appearance of retina, macula, and

symptoms should be elicited. Severe headache and jaw

optic nerve

claudication in an older person may suggest giant cell arteritis.

●

Red reflex

A previous history of migraine, diabetes mellitus,

●

Field loss

cerebrovascular disease, valvular heart disease, carotid artery

disease, or multiple sclerosis may give clues to the underlying

aetiology of the acute visual loss. It is important to take a

careful history regarding the onset of acute visual loss, as a

patient may sometimes only notice that one eye has

(longstanding) reduced vision when they inadvertently cover

the good eye.

The visual acuity gives a strong clue to the diagnosis. Poor

visual acuity such as count fingers (CF), hand movements

(HM), perception of light only (PL) or no perception of light

(NPL) suggest a severe insult to the retina or optic nerve (for

example, a vascular occlusive event).

Retinal detachment

Optic neuritis

Migraine

Floaters

Young woman

Youth

Flashing lights

Pain on moving eye

Headache

Shadow

Central scotoma

Zigzag lines

Multicoloured lights

Vascular occlusions

Field loss

Diabetes

Cerebrovascular disease

Posterior vitreous detachment

Age > 50 years

Hypertension

Elderly

Floaters

Bilateral loss

Flashing lights

Disciform macular degeneration

Sudden disturbance of central vision

Vitreous haemorrhage

Floaters

Causes and features of acute visual disturbance (in a non-inflamed eye)

ABC of Eyes

Obstruction of the red reflex on ophthalmoscopy suggests a

vitreous haemorrhage, although the patient may have a pre-

Normal vitreous

filling eye

existing cataract. The appearance of the macula, remaining

retina, and head of the optic nerve will indicate the diagnosis if

there has been haemorrhage or arterial or venous occlusion in

these areas.

If there is any uncertainty about the cause of acute visual

loss, then the patient should be referred to an eye specialist

immediately. Many of the causes are treatable if detected at an

early stage.

Retinal traction causes

Posterior vitreous detachment

flashing lights

Posterior vitreous detachment is the most common cause of the

acute onset of floaters, particularly with advancing age, and is

one of the most common causes of acute visual disturbance.

History—The patient presents complaining of floaters. In

posterior vitreous detachment, the vitreous body collapses and

detaches from the retina. If there are associated flashing lights

it suggests that there may be traction on the retina, which may

result in a retinal hole and a subsequent retinal detachment.

Examination—The visual acuity is characteristically normal,

and there should be no loss of visual field.

Management—Patients with an acute posterior vitreous

Posterior vitreous detachment causing retinal

traction and a “flashing lights” sensation

detachment should have an urgent (same day) ophthalmic

assessment, so that any retinal breaks or detachment can be

identified and treated at an early stage. The patient may

require a further visit one to two months later to exclude

subsequent development of a retinal hole.

Vitreous haemorrhage

History—The patient complains of a sudden onset of floaters,

or “blobs,” in the vision. The visual acuity may be normal or, if

the haemorrhage is dense, it may be reduced. Flashing lights

indicate retinal traction and are a dangerous symptom.

Haemorrhage may occur from spontaneous rupture of vessels,

avulsion of vessels during retinal traction, or bleeding from

abnormal new vessels. If the patient is shortsighted, retinal

detachment is more likely. If there is associated diabetes

mellitus the patient may have bled from new vessels and the

Vitreous haemorrhage

vitreous haemorrhage may herald potentially sight threatening

diabetic retinopathy.

Examination—The visual acuity depends on the extent of

the haemorrhage. Projection of light is accurate unless the

haemorrhage is extremely dense. Ophthalmoscopy shows the

red reflex to be reduced; there may be clots of blood that move

with the vitreous.

Management—The patient should be referred to an

ophthalmologist to exclude a retinal detachment. Ultrasound

examination of the eye may be useful, particularly if the

haemorrhage precludes a view of the retina. Underlying causes

Scleral coat

such as diabetes must also be excluded. If a vitreous

haemorrhage fails to clear spontaneously the patient may

Detached retina

benefit from having the vitreous removed (vitrectomy).

Traction on retina

Retinal detachment

Retinal detachment should be suspected from the history. It is

only when the detachment is advanced that the vision and the

Vascular choroid

visual fields are affected and the detachment becomes readily

visible on direct ophthalmoscopy.

Retinal detachment. Only visible on direct

History—The patient may complain of a sudden onset of

ophthalmoscopy when detachment is advanced

floaters, indicating pigment or blood in the vitreous, and

Acute visual disturbance

flashing lights caused by traction on the retina. These, however,

are not invariable and the patient may not present until there is

field loss when the area of detachment is sufficiently large or

a deterioration in visual acuity if the macula is detached.

Retinal detachment is more likely to occur if the retina is thin

(in the shortsighted patient) or damaged (by trauma) or if the

ocular dynamics have been disturbed (by a previous cataract

operation). Traction from a contracting membrane after

vitreous haemorrhage in a patient with diabetes can also cause

a retinal detachment.

Detached retinal folds—inferior detachment

Examination—Visual acuity is normal if the macula is still

attached, but the acuity is reduced to counting fingers or hand

movements if the macula is detached. Field loss (not complete

in the early stages) is dependent on the size and location of the

detachment. Direct ophthalmoscopy will not detect the

abnormality if the detachment is small; detached retinal folds

may be seen in larger detachments.

Management—The patient should be referred urgently. Only

small retinal holes with no associated fluid under the retina can

be treated with a laser, which causes an inflammatory reaction

that seals the hole. True detachments usually require an

operation to seal any holes, reduce vitreous traction, and if

necessary drain fluid from beneath the neuroretina.

A vitrectomy may be required, which is carried out using fine

microsurgical cutting instruments inserted into the eye with

fibreoptic illumination. This may be combined with the use of

special intraocular gases (for example, sulphur hexafluoride)

Retinal tear

or silicone oil to keep the retina flat. If gas is used the patient

may have to posture face down for several weeks after surgery

in cases of retinal detachment, and must not travel by air (the

intraocular gas expands at altitude) until most of the gas in the

eye has been absorbed.

Cryotherapy is used to treat the retinal

Cryotherapy (freezing treatment) is applied

Cryotherapy causes scarring, which seals the

hole causing the retinal detachment

to the sclera overlying the retinal tear

retinal hole

Infusion line

Light pipe

Ocutome

Pars plana

A piece of silicone is stitched to the scleral

Microsurgical instruments can be inserted inside

surface causing indentation, which closes the

the eye to remove the vitreous gel in

retinal hole and relieves vitreous traction

complicated retinal detachment surgery

ABC of Eyes

Arterial occlusion

Two main arterial systems that may occlude in the posterior

segment of the eye

History—The patient complains of a sudden onset of visual

●

Central or branch retinal arteries—occlusion leads to retinal

disturbance, often described as a “greyout” of the vision or as a

infarction

“curtain” descending over the vision, in one or both eyes. This

●

Posterior ciliary arteries—occlusion leads to optic nerve head

may be temporary (amaurosis fugax) if the obstruction

infarction (arteritic and non-arteritic anterior ischaemic optic

dislodges or permanent if tissue infarction occurs.

neuropathy)

Examination—In retinal artery occlusion the visual acuity

depends on whether the macula or its fibres are affected. There

may be no direct pupillary reaction if there is a complete

occlusion with a dense relative afferent pupil defect. The extent

of visual field loss depends on the area of retina affected. The

retinal artery and its branches supply the inner two thirds of

the neuroretina, and the outer third is supplied by the choroid.

The arteries may be blocked by atherosclerosis, thrombosis, or

emboli, and the attacks may be associated with a history of

Inner retina supplied

transient ischaemic attacks if the aetiology is embolic. When

by retinal vessels

Retina

the retina infarcts it becomes oedematous and pale and masks

the choroidal circulation except at the macula, which is

extremely thin—hence the “cherry red spot” appearance.

Ophthalmoscopy may be normal initially, before oedema is

established, and indeed the retinal appearance may return to

Choroid

Outer retina supplied

normal after the oedema resolves. Plaques of cholesterol or

by choroid

calcium occasionally may be seen in the vessels. In posterior

ciliary artery occlusion there is infarction of the optic nerve

Retinal

vessels

head, which has a pale swollen appearance with peripapillary

haemorrhage. This appearance may be mistaken for

papilloedema. Papilloedema, however, is usually bilateral and

the visual acuity is not affected until late in its development.

Blood supply of retina

Arterial occlusion—infarction of lower half of

Arterial occlusion—embolus

retina

Arterial occlusion—ischaemic optic nerve

Central retinal artery occlusion (CRAO) and

head pale and swollen

cherry red spot at the macula

Acute visual disturbance

Management—Giant cell arteritis must be excluded by the

history and examination, and by checking the erythrocyte

sedimentation rate. Rapid onset of second eye involvement can

occur in giant cell arteritis and this condition is an ophthalmic

Superficial temporal artery

and medical emergency. Immediate high dose intravenous

steroid therapy is indicated. Emboli from the carotid arteries

and heart should be excluded. Attempts may be made to open

up the arterial circulation in acute cases by ocular massage,

rapid reduction in intraocular pressure medically, anterior

chamber paracentesis, or by carbon dioxide rebreathing to

cause arterial dilatation. Factors predisposing to vascular

disease (for example, smoking, diabetes, and hyperlipidaemia)

should be identified and dealt with.

Venous occlusion

Temporal arteritis

History—The visual acuity will be disturbed only if the occlusion

affects the temporal vascular arcades and damages the macula.

Patients may otherwise complain only of a vague visual

disturbance or of field loss. The arteries and veins share a

Sheath

common sheath in the eye, and venous occlusion most

Artery

commonly occurs where arteries and veins cross, and in the

Sheath

head of the nerve. Thus raised arterial pressure can give rise to

Vein

venous occlusion. Hyperviscosity (for example, in myeloma)

and increased “stickiness” of the blood (as in diabetes mellitus)

Vein

will also predispose to venous occlusion. This leads to

haemorrhages and oedema of the retina. Occlusion of the

Raised blood pressure causes thickening of the arteries, which leads to

central retinal vein within the head of the nerve leads to

compression of veins

swelling of the optic disc.

Examination—Visual acuity will not be affected unless the

macula is damaged. There may be some peripheral field loss if

a branch occlusion has occurred. Ophthalmoscopy shows

characteristic flame haemorrhages in the affected areas, with a

swollen disc if there is occlusion of the central vein. An afferent

pupillary defect and retinal cotton wool spots imply an

ischaemic, damaged retina and are a bad prognostic sign.

New vessels grow on

the iris and into the

drainage angle and

cause glaucoma

Branch retinal vein

occlusion

Neovascularisation of the iris induced by

vasoproliferative factors released from the

Management—Hypertension, diabetes mellitus,

ischaemic retina

hyperviscosity syndromes, and chronic glaucoma must be

identified and treated if present. It is important to consider

systemic investigation for inherited and acquired

coagulopathies in young patients with retinal venous occlusive

disease. Antiplatelet therapy should be considered if there are

no contraindications. There is evidence that involvement of a

physician in the care of patients with retinal occlusive disease

can reduce the chance of second eye involvement and serious

systemic vascular disease.

If the retina becomes ischaemic it stimulates the formation

of new vessels on the iris (rubeosis) and subsequent

neovascularisation of the angle may lead to secondary

glaucoma. This may occur several months after the initial

venous occlusion. Such rubeotic glaucoma is a serious

condition and has the potential to render the eye both blind

and painful. Fluorescein angiography may be useful. This

involves the injection of intravenous fluorescein and sequential

Central retinal vein occlusion (CRVO)

ABC of Eyes

fundus photography with light filters to identify areas of poor

perfusion and fluorescein leakage. Laser treatment is used to

ablate the ischaemic retina in an attempt to prevent new vessel

Central dot on

Area of visual

which patient fixates

formation.

disturbance

Disciform macular degeneration

History—The patient notices a sudden disturbance of central

vision. Straight lines may seem wavy and objects may be

Distortion of

distorted, even seeming larger or smaller than normal.

straight lines

Eventually, central vision may be lost completely. This central

area of visual distortion or loss moves as the patient tries to

look around it. The layer under the neuro retina is the black

retinal pigment epithelium. Most commonly with increasing

age (the patient is normally over 60) and in certain conditions

Amsler chart: distortion seen by patient with age-related macular

(for example, high myopia) neovascular membranes may

degeneration

develop under this layer in the macular region. These

membranes may leak fluid or bleed and cause an acute

disturbance of vision.

Examination—Visual acuity depends on the extent of macular

involvement. If the patient looks at a grid pattern (Amsler chart)

the lines may seem distorted in the central area, although the

peripheral fields are normal. On fundal examination the macula

may look normal or there may be a raised area within it.

Haemorrhage in the retina is red but it appears black if it is

under the retinal pigment epithelium. There may be associated

deposits of yellow degenerative retinal products (drusen).

Management—Some cases are treatable with a laser that

occludes these neovascular membranes. The abnormal areas of

Leakage of fluid at macula (right eye)

leaking blood vessels are identified by the use of intravenous dye

injection in combination with fundus photography (fluorescein

angiography and indocyanine green angiography). A patient

who has had a subretinal neovascular membrane in one eye that

has destroyed central vision is at risk of the same thing

occurring in the other eye. The problem with laser treatment is

that it may cause immediate worsening of vision, with benefit

only in the long term. Trials are still underway to determine the

role of radiation therapy in preventing the progression of the

neovascular membranes. A recent development in the treatment

of choroidal neovascularisation is the use of photodynamic

therapy (PDT). This technique is described in Chapter 10.

Macular haemorrhage (left eye)

Optic or retrobulbar neuritis

History—The patient is usually a woman aged between

20 and 40, who complains of a disturbance of vision of one eye.

There is usually pain that worsens on movement of the eye.

There may have been previous attacks.

Examination—The visual acuity may range from 6/6 to

perception of light. Despite a “normal” visual acuity, the patient

usually has an afferent pupillary defect and may notice that the

colour red looks faded when viewed with the affected eye (red

desaturation). The field defect is usually a central field loss

(central scotoma). It is extremely important to test the field of

the other eye, as a field defect in the “good” eye may suggest a

lesion of the optic chiasm or tract (for example, a pituitary

adenoma). If the “inflammation” is anterior in the nerve, the

optic disc will be swollen. Accompanying symptoms of general

demyelinating disease such as pins and needles, weakness, and

Red as seen by

Red desaturation

incontinence suggest multiple sclerosis.

normal eye

Management—Most patients recover spontaneously, but they

may be left with diminished acuity and optic atrophy.

Treatment with steroids does not alter the visual

Treatment with systemic steroids does not alter the long term

prognosis, but it may hasten recovery in

visual prognosis but may hasten recovery. Systemic steroids may,

retrobulbar neuritis

in selected patients, reduce the incidence of subsequent

Acute visual disturbance

multiple sclerosis. Referral to a neurologist is necessary.

Debate continues regarding the use of systemic steroids and

other disease modifying agents such as interferon. If there is

doubt about the diagnosis, with atypical clinical features or

history, then the patient may need further investigation to

exclude a space occupying lesion.

Damage

Cardiovascular and cerebrovascular

disease

History—Intermittent episodes of transient visual loss

(amaurosis fugax) and bilateral permanent visual field loss may

be caused by either cardiovascular or cerebrovascular disease.

The characteristic feature of a posterior visual pathway lesion is

Damage

a homonymous nature to the hemianopic or quadrantanopic

visual field defect, which respects the vertical midline. The

patient may have a hemiparesis or hemisensory disturbance on

the same side as the visual field loss. Patients sometimes

complain of “the beginning or end of a line of print

Posterior damage

disappearing,” and some may complain of a decrease in acuity.

The visual pathways pass through a large area of the

cerebral hemispheres, and any vascular occlusion in these areas

will affect these pathways. This is in contrast to vascular lesions

in the eye or optic nerve, which either affect the whole field of

one eye or if partial tend to respect the horizontal meridian in

that eye. More posteriorly placed lesions in the brain tend to

spare the macular vision in the affected fields.

Loss of vision in one eye

Examination—The visual acuity should be preserved,

although patients may say half (either the left or right hand

side) of the Snellen chart is missing.

Management—It is important to make the diagnosis and

exclude any underlying cause for the visual pathway damage.

The following conditions should be excluded:

Homonymous hemianopia

●

Hypertension

●

Diabetes mellitus

●

Abnormal serum lipid profile

●

Hyperviscosity syndromes

●

Cardiac arrhythmias

●

Cardiac embolic disease

"Macular sparing"

Homonymous hemianopia

●

Carotid artery disease

●

Giant cell arteritis.

Damage to visual pathways from vascular lesions

The visual field defects sometimes improve with time, and

patients should be taught to compensate for their field defect

with appropriate head and eye movements. These techniques

can be taught in low vision assessment clinics.

Migraine

History—Migraine may present initially with symptoms of visual

Migraine—particular visual features

loss. The features are well known and include:

●

Zigzag lines

●

a family history of migraine

●

Multicoloured flashing lights

●

attacks set off by certain stimuli—for example, particular foods

●

fortification spectra in both eyes—these include zigzag lines and

multicoloured flashes of light

●

associated headache and nausea—although these symptoms may

not be present.

However, if patients present for the first time after 40 years

of age with migraine and associated neurological symptoms or

signs, consider the need for further investigation.

Examination—The patient may have a bilateral field defect

but this usually resolves within a few hours.

Management—Conventional treatment with analgesics and

antiemetics may be necessary. Long term prophylaxis may be

required if attacks occur often.

Gradual visual disturbance, partial sight,

and “blindness”

Causes of gradual visual loss

Retinal

degeneration

Refractive errors

The pinhole test is a most useful test for identifying refractive

Glaucoma

errors. If there is a refractive error, the vision will improve

Macular

degeneration

when the pinhole is used. A patient with thick glasses should

wear them for the pinhole test. Once other causes of visual loss

Refractive

have been excluded, the patient can be sent to an optometrist

error

Drugs

for refraction and correction of refractive error (for example,

glasses).

Corneal disease

Compressive

Cataract

lesions

Various disorders can cause gradual loss of the corneal

endothelial cells and increasing oedema of the cornea (for

example, Fuch’s endothelial dystrophy). This leads to a gradual

Causes of gradual visual loss

decrease in visual acuity that does not improve substantially

with a pinhole. If the damage is advanced the cornea may

appear opaque. A corneal graft from a donor may be required.

Cataract

This is probably the most common cause of gradual visual loss.

It can be diagnosed through testing the red reflex. The patient

should be referred if the visual disturbance interferes

appreciably with their lifestyle. If a patient with a cataract

cannot project light or has an afferent pupillary defect,

however, other diseases such as a retinal detachment must be

Cataract

excluded.

Primary open angle glaucoma

Unfortunately, the patient may not complain of visual

disturbance until late in the course of the disease; hence the

need for screening. Primary open angle glaucoma should,

however, be excluded in any patient complaining of gradual

visual loss. Establish whether there is any family history of

glaucoma. The vision may still be 6/6, so the visual field should

be checked with a red pin. Also check for cupping of, or

asymmetry between, the optic discs.

Glaucomatous cupping of the

Age-related macular degeneration

optic disc

This may occur gradually and is typified by loss of the central

field. There are usually pigmentary changes at the macula. The

disease occurs in both eyes, but it may be asymmetrical, and it

is more common in shortsighted people. The gradual

deterioration is not treatable, but if acute visual distortion

develops this may indicate a leaking area under the retina

(choroidal neovascularisation), which may respond to laser

photocoagulation or photodynamic therapy.

Macular hole

A macular hole is a full thickness absence of neural tissue at the

centre of the macula. Between 10 and 20% of full thickness

macular holes (FTMH) will become bilateral. Patients usually

present with painless loss of central vision or distortion of the

central visual field, although early macular holes may be

asymptomatic. Patients with established FTMH can be treated

with vitrectomy and instillation of intraocular gas (to provide

retinal tamponade), which have a high chance of closing the

hole successfully.

Macular hole

Gradual visual disturbance, partial sight, and “blindness”

Diabetic maculopathy

Diabetic retinopathy occurs in both insulin dependent and

non-insulin dependent diabetics and affects all age groups. The

patient may or may not give a history of diabetes, although the

longer the duration of the diabetes, the more likely the patient

is to have retinopathy. Remember that although the patient

may describe the onset of visual loss as gradual, sight

threatening diabetic retinopathy may still be present.

Non-proliferative diabetic retinopathy is typified by

microaneurysms, dot haemorrhages, and hard yellow exudates

with well defined edges. There also may be oedema of the

Background retinopathy with macular

macula, which is less easily identified but can lead to a fall in

changes and good vision: refer

visual acuity. Non-proliferative diabetic retinopathy at the

macula (diabetic maculopathy) is the major cause of blindness

in maturity onset (type 2) diabetes, but it also occurs in

younger, insulin dependent (type 1) diabetic patients. Some

forms of diabetic maculopathy may be amenable to focal laser

photocoagulation. Proliferative retinopathy, typified by the

presence of new vessels, requires urgent referral for

treatment.

Hereditary degeneration of the retina

These conditions are relatively rare (for example, retinitis

pigmentosa) but should be suspected if there is a family history

of visual deterioration. Symptoms include night blindness and

intolerance to light. Most types of retinal degeneration are not

yet treatable, but some are associated with metabolic disorders

that can be treated. These patients need to be referred to an

ophthalmologist, preferably with a special interest in these

Retinitis pigmentosa: pigmentation and

attenuated vessels

conditions, for diagnosis and any possible treatments.

Patients with severe visual impairment may develop visual

hallucinations and sleep disturbance. It is particularly

important for these patients to have an opportunity to discuss

their diagnosis and prognosis and to have genetic counselling.

Patients can be helped through psychosocial counselling (see

below, Management of gradual visual loss).

Compressive lesions of the optic pathways

These are relatively rare, but should always be considered.

Clues in the history and examination include headaches, focal

neurological signs, or endocrinological abnormalities such as

acromegaly. There should not be an afferent pupillary defect in

most patients with cataract, macular degeneration, or refractive

error. Therefore if an afferent defect is seen, suspect a

compressive or other lesion of the optic pathways. Testing of

the visual fields may show a bitemporal field defect due to a

pituitary tumour. The optic discs should be checked for optic

atrophy and papilloedema.

Drugs

Several drugs may cause gradual visual loss. In particular, a

history of excessive alcohol intake or smoking; methanol

ingestion; or the taking of chloroquine, hydroxychloroquine,

Radiograph showing calcified meningioma. Note that a plain skull

isoniazid, thioridazine, isotretinoin, tetracycline, or ethambutol

radiograph will not show most intracranial tumours

should lead to the suspicion of drug induced visual

deterioration. Systemic, inhaled, or topical corticosteroids may

cause cataracts and glaucoma.

Management of gradual visual loss

Patients with unexplained visual loss always

The initial management of gradual visual loss depends on the

should be referred

cause. Refractive errors usually require no more than a pair of

glasses. Cataracts can be removed and an artificial lens

implanted. Glaucoma requires treatment to lower the

intraocular pressure.

Cataracts

Cortical lens opacity

Cortical cataract

Nuclear sclerotic cataract

Congenital cataract

Causes of acquired cataract include:

A change in the appearance of the lens

●

Age

If you shine a bright light on the eye the lens may appear

●

Diabetes

●

Inflammation

brown, or even white if the cataract is more advanced.

●

Trauma

●

Steroids

Causes

Many conditions are associated with cataracts, but changes

within the lens associated with ageing are the most common

cause. Cataracts also occur more often in patients with diabetes,

uveitis, or a history of trauma to the eye. Prolonged courses of

steroids, both oral and topical, can also give rise to cataracts.

Children with cataracts need to be investigated to exclude

treatable metabolic conditions such as galactosaemia.

Surgery

There is no effective medical treatment for established

cataracts. The treatment is surgical.

Indications for cataract surgery

Whether or not to operate depends primarily on the effect of

the cataracts on the patient’s vision. Many years ago surgeons

waited until the cataract was mature or “ripe” (when the

contents became liquefied) because this made aspiration of the

contents of the lens easier. With advances in microsurgery,

however, there is now no longer any need to wait for the

cataract to mature, and cataract surgery can be performed at

any stage, with minimal risk.

There is no set level of vision for which an operation is

essential, but most patients with a vision of 6/18 or worse in

both eyes because of lens opacities benefit from cataract

extraction. Some elderly patients, however, may be

perfectly happy with this level of vision. Simple advice

such as the recommendation to use a good reading light that

provides illumination from above and behind, may be

adequate.

A younger patient, with more exacting visual demands, may

opt for an operation much earlier. (The minimum standard for

driving is about 6/10; equivalent to a line between 6/9 and

6/12.) With certain types of cataract, such as an opacity at the

Binocular operating microscope in position at the start of surgery

ABC of Eyes

back of the lens (posterior subcapsular cataract) the vision may

be 6/6 in dim conditions when the pupil is dilated. However, in

bright sunlight the pupil constricts and most of the light

entering the eye has to pass through the opacity, causing glare

and a fall in acuity. In this case, surgery would usually be

performed even though the tested vision was 6/6. Generally,

the surgeon’s advice is tailored to the individual patient.

Surgical techniques

“Phacoemulsification” method

Most cataract surgery in the United Kingdom is now performed

with this method. A very small tunnel incision (about 3 mm

wide) is made in the eye and a circular hole (diameter

about 5 mm) is made in the anterior capsule of the lens

Removal of the anterior capsule of the lens

(capsulorrhexis). A fine ultrasonic probe is then used to liquefy

(capsulorrhexis)

the hard lens nucleus (phacoemulsification) through this hole.

Any remaining soft lens fibres then are aspirated. A folded

replacement lens is then inserted into the empty lens capsular

bag and allowed to unfold. A high viscosity gel substance

(viscoelastic) often is used to protect the delicate endothelial

cells that line the posterior surface of the cornea during the

operation. This is then washed out at the end of the procedure.

Sutures often are not required as the tunnel incision is self

sealing. These advances in technique have considerably

improved the speed of recovery and visual rehabilitation after

cataract surgery.

Liquefaction of lens nucleus with an ultrasonic probe

Phacoemulsification equipment

through a 2-3 mm incision (phacoemulsification)

Extracapsular method

This was, until recently, the most popular method of cataract

extraction. An incision is made in the eye (about 10 mm in

length) and the anterior capsule is cut open with the tip of a

sharp needle. The large nucleus is then expressed whole and

the remaining soft lens fibres aspirated. A non-folding lens is

then inserted into the empty lens capsular bag and the incision

closed with fine sutures. The need for a larger wound in

extracapsular surgery may lead to problems with wound

security and postoperative astigmatism in some patients.

Plastic lens being inserted into the remaining clear

capsular bag of the natural lens

Extracapsular iris prolapse

Cataracts

Intracapsular method

In this method, the entire lens is removed within its capsule,

usually with a cryoprobe, after the suspensory ligaments of the

lens have been dissolved by the enzyme chymotrypsin. As there is

no remaining lens capsule, the vitreous gel in the eye can move

forward and block the flow of aqueous through the pupil. A hole

cut in the iris (iridectomy) allows the aqueous to bypass the

pupil. This method is now usually used only in special situations.

Enzyme dissolves

Anaesthesia

zonule

For most patients, cataract surgery is carried out under local

anaesthesia as a day case. Local anaesthetic can be injected

around the eye (peribulbar anaesthesia or sub-Tenon’s

anaesthesia), or, with modern, closed system, small incision,

cataract surgery, the operation can be carried out safely in

selected patients with just topical (eyedrop) anaesthesia.

Occasionally, intraocular (intracameral) local anaesthesia is

used. In certain situations general anaesthesia may be needed

because of anticipated technical difficulties or because of

patient factors (for example, in patients with Down’s syndrome

or young patients who are not cooperative).

Cryoprobe

Intraocular lens implants

The final refractive state of the eye after operation can be

chosen by measuring the curvature of the cornea

(keratometry) and the length of the eye (ultrasound biometry)

and then implanting a lens of appropriate power. An

intraocular lens implant can be more effective in correcting

refractive error than glasses and contact lenses, as it is placed in

Whole lens

the eye in the same position as the natural lens.

including capsule removed

Myopia and hypermetropia can be corrected during

cataract surgery by inserting an appropriately powered

intraocular lens. However, patients usually still require glasses

for reading or distance, as most implanted lenses have a fixed

focus. Multifocal intraocular lenses have two principal points of

focus and in theory enable the patient to have both good

Iridectomy

distance and reading vision without glasses. However, some

patients experience optical aberrations and a reduction in

contrast sensitivity with this type of intraocular lens.

Most lenses implanted nowadays are posterior chamber

lenses, which are placed in the empty lens capsular bag after

the lens contents have been removed from the eye. With this

type of lens the lens implant sits in a natural position. These

Vitreous

lenses can be folded and inserted through a minute incision

face

(2-3 mm). If the lens capsule is not present or cannot support a

posterior chamber lens unaided, the lens can be sutured in

Intracapsular cataract surgery

place. Alternatively, an anterior chamber lens, which is

supported in the anterior chamber angle, can be used. In the

past, iris clip lenses were used, but they are not used now. The

pupil should not be dilated if the iris clip type of lens has been

used, as the lens may dislocate.

Cataract surgery with lens implantations can be

combined with other intraocular surgery if necessary,

including glaucoma drainage or corneal graft surgery

Complications of cataract surgery

Over 200 000 cataract operations are performed annually in the

United Kingdom, and although modern surgical techniques

have exceptional levels of safety, complications still occur.

Patient expectations of cataract surgery are very high.

All patients should be made aware of the possible risks

of the surgery before they give their consent for the

Left: large perspex lens for extracapsular surgery. Middle: silicone foldable

operation.

lens. Right: small perspex lens, both for photoemulsification

ABC of Eyes

Infective endophthalmitis

This devastating infection occurs very rarely (about 1 in 1000

Postoperative infective

operations) but can cause permanent severe reduction of

endophthalmitis is an

vision. Most cases of postoperative infection present within two

ophthalmic emergency

weeks of surgery. Typically patients present with a short history

of a reduction in their vision and a red painful eye. This is an

ophthalmic emergency. Low grade infection with pathogens

such as Propionibacterium species can lead patients to present

several weeks after initial surgery with a refractory uveitis.

Suprachoroidal haemorrhage

Severe intraoperative bleeding can lead to serious and

permanent reduction in vision.

Ocular perforation

Sharp needles are used for many forms of ocular anaesthesia,

and globe perforation is a rare possibility. Modern forms of

ocular anaesthesia have replaced many sharp needle

techniques.

Retinal detachment

This serious postoperative complication is, fortunately, rare but

is more common in myopic (shortsighted) patients after

intraoperative complications.

Postoperative refractive error

Most operations aim to leave the patient emmetropic or slightly

myopic, but in rare cases biometric errors can occur or an

intraocular lens of incorrect power is used. Despite all efforts to

produce accurate biometry, in occasional cases the desired

Retinal detachment

refractive outcome is not achieved.

Posterior capsular rupture and vitreous loss

If the very delicate capsular bag is damaged during surgery or

the fine ligaments (zonule) suspending the lens are weak (for

example, in pseudoexfoliation syndrome), then the vitreous gel

may prolapse into the anterior chamber. This complication may

mean that an intraocular lens cannot be inserted at the time of

surgery. Patients are also at increased risk of postoperative

retinal detachment.

Uveitis

Postoperative inflammation is more common in certain types of

eyes for example in patients with diabetes or previous ocular

inflammatory disease.

Cystoid macular oedema

Accumulation of fluid at the macula postoperatively can

reduce the vision in the first few weeks after successful cataract

surgery. In most cases this resolves with treatment of the

post-operative inflammation.

Opaque posterior capsule has been cut away with a laser to clear the

visual axis

Glaucoma

Persistently elevated intraocular pressure may need treatment

postoperatively.

Posterior capsular opacification

Scarring of the posterior part of the capsular bag, behind the

intraocular lens, occurs in up to 20% of patients. Laser

capsulotomy may be needed (see Thickening of the lens

capsule, below).

Postoperative care

Most patients are treated for several weeks with steroid drops to

Postoperative care after cataract surgery

reduce inflammation and with antibiotic drops to prevent

●

Steroid drops (inflammation)

infection. Patients have traditionally been advised to avoid

●

Antibiotic drops (infection)

activities that may considerably raise the pressure in the eyeball,

●

Avoid very strenuous exertion and ocular

such as strenuous exercise or heavy lifting, for a few weeks after

trauma

the operation. However, with modern small incision surgery

Cataracts

patients can return to normal activities within a few weeks. If

sutures have been necessary, these often need to be taken out

before glasses can be prescribed because of the changes they

induce in the shape and refractive state of the eye.

Thickening of the lens capsule

The remaining lens capsule may thicken (usually over months

or years) and this may need to be cut open. In patients who

have had previous cataract surgery, capsular thickening is the

most common cause of gradually worsening vision. Division of

this thickened capsule (capsulotomy) is usually done with a

special laser (called the Q-switched neodymium yttrium-

aluminium-garnet or Nd-YAG laser), which creates microscopic

focused explosions that dissect tissue rather than burn it. This

avoids the need to open the eye surgically, and it can be

performed painlessly (the capsule has no pain fibres) on an

outpatient basis, under topical anaesthesia, with the patient

sitting at a slit-lamp microscope. This treatment has given rise

in part to patients’ commonly held misconception that

cataracts can be removed by laser alone.

Optical correction after surgery

Cataract glasses—thick, heavy, expensive, with magnified

image and reduced field of vision—are now rarely

necessary because of intraocular lens implants

Removal of the crystalline lens results in an eye with a large

hypermetropic refractive error. This refractive error is usually

corrected with an intraocular lens implant at the time of

surgery. If the implant results in clear vision for distance,

glasses usually will be required for reading fine print, as the

new lens has a fixed focus. If the patient had a cataract

extraction before intraocular lenses were used commonly,

optical correction has to be achieved with glasses or a

contact lens.

Glasses

The natural lens has great refractive power and consequently

the glasses required to correct the refractive error after cataract

extraction are thick and heavy, even when they are made of

plastic. The corrected image is about 30% larger than that seen

by the normal eye. This means that the image from an eye that

has had a cataract removed, with subsequent glasses correction,

cannot be fused with the image from the other eye, unless the

lens in the other eye is also removed. Objects are also perceived

to be closer than they are, often resulting in accidents—for

example, pouring tea into the lap rather than into the cup. The

field of vision is restricted, and there is a “blind ring” (scotoma)

within this field because of the optical aberrations inherent in

such powerful lenses. These optical problems do not occur with

contact lenses or an intraocular lens implant.

Contact lenses

The size of an image with a contact lens is only 10% larger than

the image in the normal eye. The brain can fuse this disparity

and thus both an operated eye and an unoperated eye may be

used simultaneously. However, most patients with cataracts are

elderly and problems may arise in using the contact lens

because of an inadequate tear film, difficulties with handling,

and infection.

Peripheral image distortion that may be present with

cataract glasses

Secondary intraocular lens implantation

If the problems posed by using glasses or contact lenses are too

great, secondary implantation of an intraocular lens can be

considered. However, this procedure has associated risks,

particularly in patients who have had intracapsular cataract

extraction. Complications may occur, including secondary

glaucoma. The potential advantages and disadvantages of the

various options need to be fully considered by the patient and

the ophthalmologist before a final decision is made.

Glaucoma

The glaucomas are a range of disorders with a characteristic

type of optic nerve damage. The glaucomas are the second

commonest cause of blindness in the world, and the

Block in flow

commonest cause of irreversible blindness. The most effective

through meshwork

way of preventing this damage is to lower the intraocular

pressure.

Raised episcleral

venous pressure

Normally the ciliary body secretes aqueous, which flows into

the posterior chamber and through the pupil into the anterior

chamber. It leaves the eye through the trabecular meshwork,

flowing into Schlemm’s canal and into episcleral veins. The

flow and drainage can be obstructed in several ways.

Symptoms and signs

A patient with primary open angle glaucoma (also known as

chronic open angle glaucoma) may not notice any symptoms

Flattening of iris against

Block in flow between

trabecular meshwork

until severe visual damage has occurred. This is because the

iris and lens

rise in intraocular pressure and consequent damage occurs so

slowly that the patient has time to compensate. In contrast, the

Normal aqueous drainage and possible sites of obstruction

clinical presentation of acute angle closure glaucoma is well

known, as the intraocular pressure rises rapidly and results in

a red, painful eye with disturbance of vision.

The clinical signs of raised intraocular pressure depend on

both the rate and degree of the rise in pressure

Raised intraocular pressure

Most patients with raised intraocular pressure (IOP) are

unaware that they have a problem. Raised IOP is detected most

commonly through screening as part of a routine eye test by an

optometrist. The IOP is determined by the balance between

aqueous production inside the eye and aqueous drainage out

of the eye through the trabecular meshwork. Each normal eye

makes about 2 l of aqueous a minute—that is, about 70 litres

during the course of a lifetime. In a British Caucasian

population, 95% of people have an IOP between 10 and

21 mm Hg, but IOP can drop as low as 0 mm Hg in hypotony

and can exceed 70 mm Hg in some glaucomas.

The rate at which raised IOP causes optic nerve damage

depends on many factors, including the level of IOP and

whether glaucomatous damage is early or advanced. In general,

raised IOPs in the 20-30 mm Hg range usually cause damage

over several years, but very high IOPs in the 40-50 mm Hg

range can cause rapid visual loss and also precipitate

retinovascular occlusion.

Haloes around lights and a cloudy cornea

Measuring intraocular pressure by applanation

The cornea is kept transparent by the continuous removal of

tonometry

fluid by the endothelial cells. If the pressure rises slowly, this

process takes longer to fail. When the pressure rises quickly

(acute closed angle glaucoma) the cornea becomes

waterlogged, causing a fall in visual acuity and creating

haloes around lights (like looking at a light through frosted

glass).

Pain

If the rise in pressure is slow, pain is not a feature of

glaucoma until the pressure is extremely high. Pain

is not characteristically a feature of primary open angle

Cloudy cornea after sudden rise in intraocular

glaucoma.

pressure (acute angle closure glaucoma)

Glaucoma

Visual field loss

Pressure on the nerve fibres and chronic ischaemia at the optic

nerve head cause damage to the retinal nerve fibres and usually

results in characteristic patterns of field loss (arcuate scotoma).

However, this spares central vision initially, and the patient

does not notice the defect. Sophisticated visual field testing

techniques are required to detect early visual field defects.

The terminal stage of glaucomatous field loss is a severely

contracted field, because only a few fibres from the more richly

innervated macula area survive. Even at this stage (tunnel

vision) the vision may still be 6/6.

Optic disc changes

The optic disc marks the exit point of the retinal nerve fibres

Normal distribution of nerve fibres in the retina

from the eye. With a sustained rise in IOP the nerve

fibres atrophy, leaving the characteristic sign of chronic

glaucoma—the cupped, pale optic disc.

Venous occlusion

Raised IOP can impede blood flow in the low pressure venous

system, increasing the risk of retinal venous occlusion.

Enlargement of the eye

In adults no significant enlargement of the eye is possible

Glaucomatous cupping of

because growth has ceased. In a young child there may be

the optic nerve

enlargement of the eye (buphthalmos or “ox-eye”). This tends

to occur with raised IOP in children under the age of three

years. These children may also be photophobic and have

watering eyes and cloudy corneas.

Nerve fibres

Disc

Cup

Disc

diameter

Enlarged

watering eyes

Normal Cup/Disc

with cloudy

ratio (0.3)

corneas in a child

with glaucoma

Normal disc

Atrophy

Pale disc

Primary open angle glaucoma

Primary open angle glaucoma is the most common form of

Kinked vessels

glaucoma and is the third most common cause of registration

Disc

at edge of disc

of blindness in the United Kingdom. The resistance to outflow

haemorrhages

through the trabecular meshwork gradually increases, for

‘Baring’ of

Cup

Disc

vessels

diameter

reasons not fully understood, and the pressure in the eye

(loss of support)

slowly increases, causing damage to the nerve. The level

of IOP is the major risk factor for visual loss. There may be

Increased Cup/Disc

other damage mechanisms, particularly ischaemia of the optic

ratio (0.9)

vertical > horizontal

nerve head.

Optic disc

Glaucomatous disc

changes in

Symptoms

glaucoma

Because the visual loss is gradual, patients do not usually

present until severe damage has occurred. The disease can

be detected by screening high risk groups for the signs

of glaucoma. At present most patients with primary open

Risk factors for primary open angle

angle glaucoma are detected by optometrists at routine

glaucoma

examinations.

●

Level of intraocular pressure

●

Increasing age

●

African-Caribbean origin

Groups at risk

●

Family history

The prevalence increases with age from 0.02% in the 40-49 age

●

Thin corneas

group to 10% in those aged over 80. Those with an increased

ABC of Eyes

risk include first degree relatives of patients (1 in 10), patients

with ocular hypertension (particularly those with thin corneas,

larger cup to disc ratios and higher IOPs), people with myopia,

and people of African-Caribbean origin (

5 risk in

Caucasians). Recently, genetic mutations have been identified

that account for 3-4% of primary open angle glaucomas.

Signs

The eye is white and on superficial examination looks normal.

The best signs for the purpose of detection are the optic disc

changes. The cup to disc ratio increases as the nerve fibres

atrophy. Asymmetry of disc cupping is also important, as the

disease often is more advanced in one eye than the other.

Haemorrhages on the optic disc are a poor prognostic sign.

Longer term changes in disc cupping are best detected by serial

photography, and the more recently introduced scanning laser

ophthalmoscope may be able to detect structural changes in

the nerve at an early stage of the disease.

Visual field loss is difficult to pick up clinically without

specialised equipment until considerable damage (loss of up to

Computerised visual field test print out showing

50% of the nerve fibres) has occurred. Computerised field

“tunnel” vision

testing equipment may detect nerve fibre damage earlier,

particularly if certain types of stimuli such as fine motion or

blue on yellow targets are used. Computer assisted field testing

is also the best method for detecting long term change and

deterioration of visual fields.

The classical signs of glaucoma (field loss and optic disc

cupping) often are seen in patients who have pressures lower

than the statistical upper limit of normal (21 mm Hg).

However, many clinicians now feel that these two glaucomas are

part of the same spectrum of pressure dependent optic

neuropathies, although these patients are sometimes referred

to as having normal tension glaucoma. For an accurate

measurement of IOP, intraocular pressure phasing, taking

multiple measurements throughout the day is useful, so that

any spikes can be detected.

Normal optic disc

In normal tension glaucoma there may be a significant

component of vascular associated damage at the optic

nerve head (ischaemia or vasospasm). Management of

progressive normal tension glaucoma involves lowering IOP.

Drug induced nocturnal hypotension should be considered in

progressive normal tension glaucoma.

Cupped optic disc

Visual field

testing with

computerised

field testing

equipment

Acute angle closure glaucoma

Acute angle closure glaucoma is probably the best known

type of glaucoma, as the presentation is acute and the affected

Advanced scanning laser image of cupped optic nerve head

Glaucoma

Increased resistance

to flow between iris

and lens.

Iris lax

Iris is taut

Build up of aqueous

pushes iris forward,

blocking trabecular

meshwork

Small pupil

Semidilated pupil

Acute angle closure glaucoma

eye becomes red and painful. In angle closure glaucoma,

apposition of the lens to the back of the iris prevents the

flow of aqueous from the posterior chamber to the anterior

chamber. This is more likely to occur when the pupil is

semi dilated at night. Aqueous then collects behind the iris

and pushes it on to the trabecular meshwork, preventing the

drainage of aqueous from the eye, so the IOP rises rapidly.

Symptoms

The eye becomes red and painful because of the rapid rise in

IOP, and there is often vomiting. Vision is blurred because the

cornea is becoming oedematous; patients may notice haloes

around lights due to the dispersion of light through the

waterlogged cornea. They may have a history of similar attacks in

the past that were aborted by going to sleep. During sleep the

pupil constricts and may pull the peripheral iris out of the angle.

Acute angle closure glaucoma

Groups at risk

This type of glaucoma usually occurs in longsighted people

(hypermetropes), who tend to have shallow anterior chambers

and shorter axial length eyes. With increasing age the lens tends

to increase in size and crowd the anterior segment structures in

For acute angle closure glaucoma,

these eyes. Women have shallower anterior chambers and live

emergency treatment is required to

longer and therefore are more at risk of this type of glaucoma.

preserve the sight of the eye

Signs

Visual acuity is impaired, depending on the degree of corneal

oedema. The eye is red and tender to touch. The cornea is hazy

because of oedema, and the pupil is semidilated and fixed to

light. The attack begins with the pupil in the semidilated

position and the rise in pressure makes the iris ischaemic and

fixed in that position. On gentle palpation the affected eye feels

much harder than the other. Patients often are systemically

unwell with nausea, vomiting, and severe pain or headache.

If the patient is seen shortly after an attack has resolved,

none of these signs may be present, hence the importance of

the history.

Management

Emergency treatment is required to preserve the sight of the eye.

If it is not possible to get the patient to hospital immediately,

acetazolamide 500 mg should be given intravenously, and

pilocarpine 4% instilled in the eye to constrict the pupil.

Hole made in the iris (iridotomy) with the

The IOP must first be brought down medically, and a hole

Neodymium yttrium-aluminium-garnet

(peripheral iridotomy) subsequently must be made in the

(Nd-YAG) laser without having to cut into

peripheral iris, either with a laser or surgically, in order to

the eyeball

ABC of Eyes

restore aqueous flow. The other eye should be treated similarly,

Effects of topical steroids

as a prophylactic measure.

●

Topical steroids may cause a change in the

If the treatment is delayed, adhesions may form between

drainage meshwork, resulting in a slow rise in

the iris and the cornea (peripheral anterior synechiae) and the

intraocular pressure

trabecular meshwork itself may be damaged. A surgical

●

Patients may not complain of visual symptoms until

drainage procedure may then be required. Angle closure

severe damage has occurred

glaucoma is a very serious condition and even with optimum

management the patient may need multiple surgical

procedures and have impaired vision. Sometimes laser burns

can be made on the iris (iridoplasty) without creating a full

thickness hole in the iris. This treatment causes the iris to

contract away from the occluded drainage angle.

Other types of glaucoma

If there is inflammation in the eye (anterior uveitis), adhesions

may develop between the lens and iris (posterior synechiae).

These adhesions will block the flow of aqueous between the

posterior and anterior chambers and result in forward

New vessels on the iris causing rubeotic

ballooning of the iris and a rise in the IOP. Adhesions may also

glaucoma

develop between the iris and cornea (peripheral anterior

synechiae), covering up the trabecular drainage meshwork.

Inflammatory cells may also block the meshwork. Topical

steroids may cause a gradual asymptomatic rise in IOP that can

lead to blindness. (Patients taking topical steroids over a long

period should always be under ophthalmological supervision.)

The growth of new vessels on the iris (rubeosis) occurs both

in diabetic patients and after occlusion of the central retinal

vein resulting from retinal ischaemia. These vessels also block

the trabecular meshwork causing rubeotic glaucoma, which is

extremely difficult to treat.

The trabecular meshwork itself may have developed

abnormally (congenital glaucoma) or been damaged by trauma

to the eye. Patients who have had eye injuries have a higher

chance than normal of developing glaucoma later in life. If

there is a bleed in the eye after trauma, the red cells may also

Keratic precipitates

block the trabecular meshwork.

Medical treatment

The main aim of therapy in glaucoma management is

reduction of IOP. There is now good evidence from multiple

It is important to remember that drops

large randomised trials that reducing IOP is effective in

used to treat glaucoma contain powerful

preventing disease progression in ocular hypertension, primary

drugs that can have marked systemic side

open angle glaucoma, and even in so-called normal tension

effects, despite the low topical doses used

glaucoma. Target pressures in the low teens are associated with

the lowest progression rates.

blockers ( for example, timolol, levobunolol, carteolol, betaxolol, and

metipranolol)

These reduce the secretion of aqueous and are still the most

commonly prescribed topical treatment. Contraindications to

their use include a history of lung or heart disease, as the drops

may cause systemic blockade. It is important to be aware that

topical blockers can unmask latent and previously

undiagnosed chronic obstructive airway disease in elderly

people. Systemic effects from eye drops can be reduced by

occlusion of the punctum (finger pressed on the caruncle,

which can be felt as a lump at the inner canthus of the eye) or

shutting the eyes for several minutes after putting in the drops.

This reduces the lacrimal pumping mechanism and stops the

eyedrops running down the lacrimal passages and being

absorbed systemically via the nasal mucosa or by inhalation

directly into the lungs. This may also enhance ocular

Eye closure to reduce systemic side effects

absorption of the drugs. These drops are usually given twice a

after instilling drops

Glaucoma

day, but long acting forms now available can be given once

a day, either alone or in combination with other drops.

Prostaglandin analogues ( for example, latanoprost,

travoprost, and bimatoprost)

These reduce the IOP by increasing aqueous outflow from the

eye via an alternative drainage route called the uveoscleral

pathway. It is possible to get reductions in IOP of up to 30-35%

with these drugs. This ability to achieve larger reductions in

IOP with improved systemic safety profiles has been a major

therapeutic advance in glaucoma. Systemic side effects are

minimal but an unusual side effect in a few patients with light

irides is a gradual, permanent darkening of the iris. Patients

often notice that their eyelashes increase in length and darken.

Longer, thicker lashes on right eyelid after prostaglandin

For optimum effect, these drops are used once daily (at night).

treatment

Sympathomimetic agents

Topical adrenaline, once commonly prescribed, is now rarely

used because of lack of efficacy compared with blockers and

adverse effects on the conjunctiva. A newer generation of agents

that stimulate the receptors of the sympathetic system is now

used—for example, brimonidine (used twice a day) or

apraclonidine. Contraindications include cardiovascular disease,

because of the potential systemic sympathomimetic effects.

Parasympathomimetic agents ( for example, pilocarpine)

These constrict the pupil and “pull” on the trabecular

meshwork, increasing the flow of the aqueous out of the eye.

The small pupil may, however, cause visual problems if central

lens opacities are present. Constriction of the ciliary body

Small pupil with pilocarpine drops

causes accommodation and blurred vision in young patients.

Pilocarpine should not be used if there is inflammation in the

eye, as the pupil may stick to the lens close to the visual axis

(posterior synechiae) and affect vision. Pilocarpine is usually

administered four times a day but can be used twice daily in

a combined form with a blocker, or once at night in a gel

preparation, which reduces side effects. When patients first

instill pilocarpine they often experience a marked brow ache,

which tends to reduce with longer term use of the drug.

Pilocarpine therapy can increase the risk of retinal detachment.

Carbonic anhydrase inhibitors

These are available as topical (for example, dorzolamide,

brinzolamide) or oral (for example, acetazolamide) agents.

They reduce the secretion of aqueous, and the systemic form,

administered orally, is the most powerful agent for reducing

IOP, although unfortunately it may have side effects, including

Mild allergy to the active drug component of

nausea, lassitude, paraesthesiae, electrolyte disturbances, and

a glaucoma medication

renal stones. The topical form has minimal systemic side

effects. Carbonic anhydrase inhibitors should not be used in

patients with sulphonamide allergy.

Neuroprotective agents

Experimental evidence exists that some neuroprotective agents

may reduce intraocular pressure induced glaucomatous

damage. However, at present there is no conclusive evidence

that these agents are helpful in glaucoma, but large scale

clinical trials are currently being carried out in this area.

Allergy to glaucoma drops

The main symptoms of drop allergy are intense itching

and irritation of the eyes and eyelids, which are exacerbated

by instillation of the drops. The characteristic signs of drop

hypersensitivity include red injected eyes, red swollen

eyelids, and ezcema like excoriation of the eyelids and

Severe allergy: bilateral allergic dermatitis secondary to

periocular skin.

the preservation component in a glaucoma drop

ABC of Eyes

The patient may be hypersensitive to the active glaucoma

drug or one of the preservative agents used to stabilise the

Trabecular

Cornea

preparation (usually benzalkonium chloride).

meshwork

The diagnostic test for drop hypersensitivity is controlled

Iris

cessation of therapy. Symptoms and signs should rapidly

improve on withdrawal of the topical therapy. When patients

are on multiple topical agents it can be difficult to isolate the

agent responsible for the allergic reaction. In cases of allergy to

Laser beam

the preservative agent in the drugs, some topical

drugs used in glaucoma management are available in

preservative free form.

Contact lens

Laser treatment

Laser beam

Laser trabeculoplasty

Argon or diode laser “burns” are applied to the trabecular

meshwork. How this treatment works is uncertain. It was

thought to contract one part of the meshwork, so stretching

and opening up adjacent areas, but a more recent hypothesis is

that it rejuvenates the cells in the trabecular meshwork. This

treatment is used only in the types of glaucoma where the

drainage angle is open. Its effect is relatively short term, so this

Laser trabeculoplasty

treatment is mainly used for more elderly patients.

Laser iridotomy

Peripheral laser iridotomy (PI) can be performed in cases of

angle closure glaucoma with the Nd-YAG laser, which (unlike

argon or diode lasers) actually cuts holes in tissue rather than

just burning. This procedure can be performed without

incising the eye.

Diode laser with

Laser iridoplasty

transillumination to locate

Argon laser iridoplasty is a useful procedure in some forms of

ciliary body

angle closure glaucoma. A ring of laser burns is applied to the

peripheral iris, causing contraction of tissue. This pulls the

peripheral iris away from the drainage angle and helps to

reduce angle occlusion.

Laser ciliary body ablation

Lasers can be used to burn the circular ciliary body that

produces the aqueous humour. At the correct wavelength the

laser radiation passes through the white sclera and is only

Surgical peripheral

absorbed by the pigmented ciliary body (transcleral ciliary

iridotomy

body cycloablation). This treatment is now commonly

performed with a diode laser and usually has to be repeated to

maintain lowering of IOP. Most patients undergoing laser

Conjuctiva

ciliary body ablation need to continue medical therapy. Laser

and Tenon‘s capsule

destruction of the ciliary body usually is used only in advanced

Subconjuctival space

refractory glaucomas or where other surgical options are

Ciliary body

limited.

Scleral flap

Peripheral iridectomy

Aqueous draining through

fistula

Surgical treatment

Iris

Surgery was traditionally used only when treatment had

failed to halt the progress of glaucoma, but there is some

evidence that earlier surgical intervention is beneficial for

selected patients.

Iridectomy

Peripheral iridectomy is performed in cases of angle

closure glaucoma, both in the affected eye and prophylactically

in the other eye. Most of these cases can be treated with the

Nd-YAG laser. Surgery is reserved for difficult or refractory

cases.

Trabeculectomy

Glaucoma

Drainage surgery

When it is not possible to achieve the target IOP with medical

(or laser) therapy in glaucoma, then the next line of

management is surgical. The most effective glaucoma filtration

procedure is trabeculectomy. In this procedure a guarded

channel is created, which allows aqueous to flow from the

anterior chamber inside the eye into the sub-Tenon’s and

subconjunctival space (bypassing the blocked trabecular

meshwork). A drainage “bleb” (aqueous under the conjunctiva

and Tenon’s capsule) can often be seen under the upper lid.

Conjunctivitis in a patient with a drainage bleb should always

Bleb

be treated promptly, as there is an increased risk of the

infection entering the eye (endophthalmitis).

Possible complications

The main cause of surgical failure is postoperative scarring of

the drainage channel and drainage bleb. Scarring can be

reduced by using adjuvant antiscarring therapy. Various

antiscarring agents are used, including drugs used in

anticancer therapy. These are delivered by short applications

during surgery to the drainage bed on a sponge or by

postoperative injections. The most commonly used drugs

are 5-fluorouracil and mitomycin-c.

Glaucoma filtration procedures do carry some risk and the

Sponges soaked in 5-fluorourcil to prevent

patient should be advised of the risk of postoperative cataract

postoperative scarring

and hypotony (low pressure) and the possibility of a reduction

in postoperative best corrected visual acuity.

Although trabeculectomy remains the gold standard

Support group

glaucoma filtration procedure, several alternative filtration

The International Glaucoma Association is the major support

operations also exist. Non-penetrating deep sclerectomy and

group for patients with glaucoma in the United Kingdom. This

viscocanalostomy have good safety profiles but have tended to

organisation provides information pamphlets and support for

produce less dramatic reductions in IOP in all published trials.

people with different forms of glaucoma

For certain patients with refractory glaucoma, a tube

International Glaucoma Association

drainage device may be considered. A drainage tube is inserted,

King’s College Hospital

Denmark Hill, London SE5 9RS

connecting the anterior chamber of the eye with a reservoir in

Tel/fax: 020 7737 3265

the posterior orbit. This has a good chance of controlling IOP,

Email: iga@kcl.ac.uk

but also has moderately high risk of serious complications.

Age-related macular degeneration

Age-related macular degeneration (ARMD) is the late stage of

age-related maculopathy and the most common cause of

blindness in developed countries. The condition is characterised

by progressive, bilateral atrophic changes in the choriocapillaris,

Bruch’s membrane, and the retinal pigment epithelium. The

incidence of blinding ARMD increases sharply with increasing

age, and it is present in about 15% of all people over the age of 85.

ARMD can be divided clinically into dry (atrophic) and wet

(exudative) forms.

Dry (atrophic, non-exudative) ARMD

This is the common form of ARMD; about 85% of all ARMD is

of this type. It is characterised by widespread atrophic changes

in the macular area and is bilateral. Dry ARMD usually

progresses only slowly and with great variability and may result

in severe visual impairment over five to ten years in some

Dry age-related macular degeneration with drusen in the macula area

patients.

Wet (exudative, neovascular) ARMD

Wet ARMD is a more aggressive disease and although only

15% of all ARMD cases are of this type, the exudative form is

responsible for 90% of all severe visual loss in ARMD. The

clinical course of the disease is much more rapid than dry

ARMD and 75% of patients will have a marked reduction in

vision over about three years. The chance of second eye

involvement in wet ARMD is very high.

In wet ARMD the problem stems from an abnormal growth of

new blood vessels (choroidal neovascularisation) that invade the

retina from the choroid. These abnormal blood vessels leak fluid

and are associated with bleeding in the macular region.

Various associated risk factors for the

development and progression of ARMD

Risk factors for ARMD

have been suggested, including:

●

female sex

The aetiology of ARMD is multifactorial and currently is not

●

positive smoking history

fully understood. The main risk factor for the development of

●

positive family history

this degenerative condition seems to be increasing age.

●

hypertension

●

raised cholesterol

●

history of previous high exposure to

ultraviolet light

●

hypermetropia

●

cataract surgery

Central dot on

Area of visual

which patient fixates

disturbance

Distortion of

straight lines

Amsler chart to assess patients who have distortion

Amsler grid: distortion seen by patient with age-related macular

of their central vision

degeneration

Age-related macular degeneration

Clinical presentation

Most patients with dry, atrophic ARMD present with a gradual

reduction in the central vision of both eyes, which affects their

Drusen

Photoreceptors

ability to read, to recognise faces, and to see clearly in the

distance. Patients may notice mild distortion of their central

vision (metamorphopsia) but characteristically retain a good

peripheral visual field.

In the wet, exudative form of ARMD, patients present more

acutely with a sudden change in their central vision (usually in

one eye initially). They often experience marked central

distortion (“straight lines have a bend in the middle”) or

a precipitous fall in their vision.

Signs in dry ARMD

Bruch‘s membrane

Choroid

The earliest clinically detectable sign of dry ARMD is the

appearance of drusen in the macular region of both eyes.

Sclera

Retinal pigment

epithelium

Drusen are tiny pinpoint, discrete yellow deposits, which

correspond histopathologically to focal accumulations of

abnormal hyaline material located specifically at the interface

of Bruch’s membrane and the retinal pigment epithelium

(RPE). Later atrophic changes occur in the macular area,

causing a diffuse pale, mottled appearance. This appearance

corresponds histopathologically to atrophy of the RPE and

choroid, with some areas of secondary RPE hyperplasia. In

advanced geographical atrophy of the macula there is a large,

well demarcated area of atrophy and it is possible to see clearly

the underlying choroidal vessels.

Signs in wet ARMD

Dry macular degeneration

As in dry ARMD, there are drusen and atrophic changes at the

macula, but the distinctive signs of wet ARMD relate to the

abnormal growth of new blood vessels and leakage of serous

fluid and blood into the macula region. Choroidal

neovascularisation appears as a small, focal, pale pink-yellow or

grey-green elevation at the macula. There may be associated

exudation of serous fluid or blood in the subretinal or sub-RPE

space.

Blood and

Drusen

fluid exudation

Photoreceptors

Investigation

Fundus fluorescein angiography (FFA), sometimes augmented

with indocyanine green angiography (ICG), is used to confirm

the presence of an area of choroidal neovascularisation at the

macula. In both techniques, intravenous administration of

a dye allows assessment of the retinal and choroidal circulations

and highlights areas of macular pathology (particularly the

presence of abnormal, leaking blood vessels). Fundus

Choroidal

fluorescein angiography is a safe and commonly performed

Bruch‘s membrane

Choroid

neovascularisation

investigation in ophthalmic practice. However, very rarely a

patient may experience a serious episode of laryngeal oedema,

Retinal pigment

Sclera

bronchospasm, or anaphylactic shock as a result of the

epithelium

fluorescein injection. On the basis of fluorescein angiography,

choroidal neovascularisation can be divided into classic

(neovascularisation fully delineated) and occult (full extent of

neovascularisation not visible). The classic form usually

progresses faster than the occult form.

Management of ARMD

The ophthalmologist has a very important role in managing

patients with ARMD, even though very little can be done at

present to influence the natural progression of the disease in

Wet macular degeneration

the majority of patients. When told that they have ARMD, most

patients will immediately worry about the risk of total

ABC of Eyes

blindness. Although ARMD will almost certainly cause

On the basis of FFA findings subfoveal choroidal

a progressive reduction in central visual acuity in many patients,

neovascularisation can be divided into four categories

the rate of deterioration is extremely variable, and most

●

Classic with no occult—lesions that are composed of classic

patients will continue to lead active independent lives with full

choroidal neovascularisation with no evidence of an occult

preservation of their peripheral visual fields. The

component

ophthalmologist has a key role here in demonstrating to the

●

Predominantly classic with occult—lesions in which 50% or more of

patient that the peripheral visual fields (to confrontation) are

the entire area is classic choroidal neovascularisation but some

full. Together with appropriate information about ARMD and

occult choroidal neovascularisation is present

●

Minimally classic—lesions in which less that 50% but more than

self help groups, this reassurance is the essential component of

0% of the area is classic choroidal neovascularisation

the consultation.

●

Occult only—lesions in which there is occult choroidal

The patient can be offered visual rehabilitation (refraction

neovascularisation with no evidence of classic choroidal

and low vision assessment) and registration as partially sighted

neovascularisation

or blind (see Chapter 7). Specific advice about diet and lifestyle

At present the main treatment effect of PDT is seen in classic

measures can be offered, based on recent research findings in

lesions with no occult

this field. Much interest in recent years has focussed on the

From Guidance on the use of photodynamic therapy for age-related

possible role of dietary supplementation in ARMD, and recent

macular degeneration. London: NICE, 2003

evidence suggests that the progression of ARMD in some

patients can be reduced by vitamin supplementation. A

balanced diet (rich in fresh fruit and green leafy vegetables) is

important and this can be supplemented by preparations

containing multivitamins, vitamin C, vitamin A and

beta-carotene, zinc, omega 3 fatty acids (found in fish), lutein,

and xeaxanthin.

Specific management of wet ARMD

Treatments specifically for wet ARMD aim to close off blood

flow through the area of choroidal neovascularisation, to allow

resolution of the exudative changes at the macula and the

restoration of central visual function. The first stage is to

determine whether the patient is in the subgroup of ARMD

patients for whom ablation of the choroidal neovascularisation

is effective. Patients with severe secondary fibrotic changes in

the delicate tissues of the macula are less likely to regain visual

function through this treatment. The pattern of choroidal

neovascularisation, determined using fundus fluorescein

angiography and indocyanine green angiography, is also very

important. Monitoring of patients who have been treated for

wet ARMD is essential, because the choroidal

Subfoveal choroidal neovascularisation—classic with no occult. Increasing

neovascularisation can recur.

“lacy” hyperfluorescent dye leakage from the abnormal blood vessels is

Several different methods of ablation of choroidal

clearly demarcated

neovascularisation are available for treating wet ARMD.

Laser photocoagulation

The neovascularisation is occluded by direct laser

photocoagulation. In the process of destroying the deeper

abnormal vessel leakage, the overlying retina also sustains

significant damage. This type of treatment is often used for

extrafoveal and juxtafoveal choroidal neovascularisation that

does not lie directly beneath the fovea. In subfoveal disease

laser photocoagulation will result in an immediate reduction in

vision.

Photodynamic therapy (PDT)

This new technique uses a light activated photosensitiser

(verteporfin), given intravenously. An ophthalmic laser

delivery system is used to generate the specific wavelength of

light to activate the photosensitiser, which causes

photochemical damage and vessel occlusion in the selected

target area. This makes it possible to cause vessel occlusion

without damage to the retina, which has the advantage of

preserving visual function, particularly with choroidal

neovascularisation in the subfoveal region. PDT has become

Subfoveal choroidal neovascularisation—occult. Increasing diffuse

the treatment of choice in subfoveal choroidal

hyperfluorescent dye leakage with the source of leakage unable to be

neovascularisation.

clearly defined

Age-related macular degeneration

External beam radiation

Precisely focused radiotherapy is used to ablate the neovascular

membrane. This treatment is currently undergoing evaluation

in certain centres.

Agents that inhibit choroidal neovascularisation

A variety of agents that may inhibit subfoveal choroidal

neovascularisation are being investigated. These include

novel molecules such as antibodies and aptamers (RNA-like

molecules). The molecules neutralise growth factors such as

vascular endothelial growth factor, which stimulates new vessel

growth. Anti-angiogenic steroids are also being tested.

Submacular surgery

This is an operation involving microsurgical vitrectomy to

remove the vitreous gel, combined with a retinal incision and

then removal of the choroidal neovascularisation. This

technique may be appropriate for selected cases.

Subfoveal choroidal neovascularisation—predominantly classic with occult

Macular rotation or transposition surgery

This is a complex surgical technique in which the macular

region of the retina is physically moved to overlie another area

of healthy retinal pigment epithelium elsewhere in the adjacent

retina. Subsequent strabismus surgery is need to rotate the

macula back into the primary position. This complicated

operation is still under development and carries significant risk

at present.

Retinal transposition with macular rotation

Squint

Many practitioners approach the subject of squint (strabismus)

with great trepidation, sometimes with justification. However, if

it is approached systematically, much of the myth and mystery

can be dispelled.

What is a squint?

The word is used in many different ways. It is often used to

describe the narrowing of the gap between the upper and lower

eyelids (interpalpebral fissure), usually carried out by patients to

create a pinhole effect. This reduces the consequences of any

refractive error, and improves the clarity of the image. However,

the true definition of squint is that one of the eyes is not

directed towards the object under scrutiny. Note that if the eyes

Abnormal eye

Normal eye

converge for close work, this does not indicate a squint.

Blurred image

Clear image

Image suppressed

Clear image

resulting in

amblyopia

One eye not directed

towards the object of

regard

The true definition of squint

Eye wanders

Eye stays straight

A squint may be a sign of impaired visual acuity

Why is a squint important?

A squint may show that the acuity of the eye is impaired

because of ocular disease. The eyes are kept straight by the

drive to keep the image of the object being viewed in the

centre of the macular area, where highest definition and colour

vision is located. The tone in the extraocular muscles is

constantly being readjusted to maintain this fixation. If the

vision is impaired in one or both eyes this constant

A squint is important

readjustment cannot occur and one eye may wander.

●

A squint may show that the acuity of the eye is impaired

The squint is an important sign, as the cause of impaired

●

A squint may itself cause amblyopia in a child

vision may be eminently treatable, such as a cataract or a

●

A squint may be a sign of a life threatening condition

refractive error. It is especially important in a child because,

Squint

unlike the vision of an adult, a child’s vision may be irreversibly

impaired if treatment is not given in time. The visual pathways

in the brain that receive information from an abnormal eye fail

to develop normally. The resulting depressed cortical function

leads to amblyopia, commonly called a “lazy” eye. The child

does not usually complain that the sight of one eye is poor.

A pair of glasses to correct a refractive error may prevent a

permanently impaired acuity.

Congenital cataract

A squint may itself cause amblyopia in a child. Misalignment

of the eyes may be the primary problem, with resulting double

vision. Young children do not normally complain of double

vision. In a young child the vision of one eye may be suppressed

to avoid this diplopia and the visual pathways then fail to

develop properly. This leads to amblyopia of the eye that is

otherwise organically sound.

A squint may be a sign of a life threatening condition.

Squint is a common presentation in a child with a

retinoblastoma. The resulting squint is non-paralytic and

therefore the angle of deviation is the same, irrespective of the

direction of gaze. The eye deviates because vision is impaired

and this may occur in any eye with visual impairment.

A squint can also be caused by a sixth nerve palsy resulting

from a tumour causing raised intracranial pressure. In this case

the squint will be paralytic and the angle of squint will vary

depending on the direction of gaze. Patients with myasthenia

Retinoblastoma in a child presenting with a

gravis may present with a squint and diplopia.

squint

Clinical detection and assessment

Adults may complain of deviation of the eyes or of diplopia. For

children, parents usually notice either one or both eyes turning

Patients with myasthenia gravis may present

in or out, or there may be a family history of squint. Children

with squint and diplopia

may also be referred from vision screening clinics.

History

A family history of squint is a strong risk factor in the

development of squint, and if there is any doubt the child

should be referred. Children with disorders of the central

nervous system such as cerebral palsy have a higher incidence

of squint. Squint is more common in preterm infants. Problems

during birth and retarded development also increase the

likelihood of a squint. The parents’ visual problems should be

ascertained, particularly large refractive errors.

The earlier the age of onset, the more likely it is that an

operation will be needed. A constant squint has a worse visual

prognosis than one that is intermittent.

Examination

Check the visual acuity

Left convergent squint: note position of light reflexes

If the visual acuity does not correct with glasses or a pinhole,

ocular disease or amblyopia must be suspected. This is

particularly important in children, as the amblyopia or ocular

problems must be treated immediately if sight is to be preserved.

Visual acuity in infants is difficult to assess. A history from the

parents is useful to find out whether the baby looks at them and

Infant vision testing is a time consuming procedure, but

at objects. However, if only one eye is affected the visual problem

with patience it is possible to quantify the visual acuity

may not be apparent. If the sight is poor in only one eye, covering

even in young children by using matching techniques for

the good eye may make the child try to push the cover away.

pictures and optotypes (for example, LogMAR Kays

picture matching cards)

Look at the position of the patient’s eyes

Large squints will be obvious. Wide epicanthic folds may give

the impression of a squint (pseudosquint), but children with

wide epicanthic folds may still have true squints.

ABC of Eyes

Look at the corneal reflections of a bright light held in front of the eyes

Note the position of the reflections; they should be

symmetrical. This test gives a rough estimate of the angle of any

deviation.

Cover test

Two types of cover test help to reveal a squint, especially if it is

small and the examiner is unsure about the position of the

corneal reflections.

●

In the cover and uncover test, one eye is covered and the

other eye is observed. If the uncovered eye moves to fix on

the object there is a squint that is present all the time—a

manifest squint. The test should then be carried out on the

other eye. A problem arises when the vision in the squinting

eye is reduced, and the eye may not be able to take up

fixation. This emphasises the need to test the vision of any

patient with squint. If the cover and uncover test is normal

(indicating no manifest squint) the alternate cover test

should be done.

Fixing eye covered

Other eye moves

●

In the alternate cover test, the occluder is moved to and fro

to take up fixation

between the eyes. If the eye that has been uncovered moves,

then there is a latent squint.

Cover and uncover test

Test eye movements in all directions of gaze

If there is a paralytic squint, the degree of deviation will vary

with the direction of gaze. An adult will often say that the

separation of the images varies and that it increases in the

direction of action of the weakened muscles.

Examination of the eye with a pupil dilating agent (mydriatic) and a

ciliary muscle relaxing agent (cycloplegic)

Any overt abnormalities of the eye should be noted. Dilating

the pupil allows you to check for retinal disease, such as a

retinoblastoma, and the cycloplegic allows a check for any

refractive error. Adequate examination of the peripheral

fundus and refraction require dilation of the pupil and special

One eye covered

equipment. Cataracts and other opacities in the media, and the

white reflex suggestive of retinoblastoma, may be checked

without dilating the pupil, by observing the red reflex.

Eye moves to take

Cover moves across

up fixation

White reflex of retinoblastoma

Alternate cover test

Management

Paralytic squints

Paralytic squints usually occur in adults. Underlying conditions

such as raised intracranial pressure; compressive lesions; and

diseases such as diabetes, hypertension, myasthenia gravis, and

dysthyroid eye disease should be excluded.

If diplopia is a problem, one eye may need to be occluded

temporarily, for example, by a patch stuck to the patient’s glasses.

Alternatively, temporary prisms may be stuck on to the glasses to

eliminate the diplopia. An operation on the ocular muscles may

be indicated if the squint stabilises. If an operation on the

muscles is either inappropriate or proves inadequate, permanent

prisms may be incorporated into the glasses’ prescription.

Test eye movements in all directions of gaze

Squint

Botulinum toxin is a recent addition to the diagnostic and

therapeutic options in squint management. When injected into

an extraocular muscle (under electromyographic control), the

toxin produces a temporary reversible paralysis of the muscle.

This technique can be used to alter extraocular muscle balance

and correct squint, and it can be used to help predict the

outcome of extraocular muscle squint surgery.

Non-paralytic squints

Non-paralytic squints usually occur in children. If the squint is

caused by disease in the eye that is causing reduced vision and

subsequent deviation of the eye (for example, cataract) this

needs to be treated. Treatments for non-paralytic squints are

Abnormal eye

Normal eye

described below.

Spectacles

There are two main indications for prescribing glasses for

children.

●

A child who is hypermetropic (longsighted) and has a

convergent squint. Normally when the ciliary muscle

contracts the lens becomes more globular to allow the eye to

focus on close objects (accommodation). This is linked to

Blurred image

Clear image

convergence so that both eyes can fix on the close object. If

the child is hypermetropic the ciliary muscle has to contract

strongly for the child to be able to focus on a near object.

This excessive accommodation may cause overconvergence so

that a squint occurs. This type of squint is called an

accommodative convergent squint. The use of hypermetropic

glasses in this case relaxes the ciliary muscles and removes

the drive to overconverge.

Image suppressed

Clear image

resulting in

amblyopia

Hypermetropic eye viewing object at a distance

Child accommodates to focus, leading to convergence

and squint

Eye wanders

Eye stays straight

Correcting lens (no accommodation required)

no convergence hence no squint

Use of spectacles to treat an accommodative convergent

squint in a longsighted child

●

A child who has a refractive error, particularly if this is

unilateral. Because of the refractive error the image on the

Hypermetropic eye

Normal eye

retina will be indistinct. The visual pathways will then not

with spectacle correction

develop properly (resulting in amblyopia). Children with a

refractive error may not develop a squint until the vision is

poor in one eye, which emphasises the need to check the

visual acuity. Glasses may prevent a child from developing

severe visual loss in an otherwise “normal” eye—hence the

need to refract every child with a squint or impaired vision.

Clear image

Occlusion

No amblyopia

No squint

This is the well known patching of one eye to encourage the

development of the visual pathway of the “bad” eye. If the

development of one pathway has been retarded by a squint or

Amblyopia and squint caused by refractive error, and the use of

refractive error this pathway can be stimulated if the “good” eye

spectacles to treat the refractive error and prevent amblyopia

ABC of Eyes

is patched. However, this can only be done for a limited period,

and there is a danger of the good eye itself becoming

amblyopic. Most clinicians feel that after the age of about

seven, occlusion therapy is unlikely to be helpful. In the

meantime, the underlying problem must, of course, be

corrected.

The vision of the good eye may also be “blurred” with drops

such as atropine. Although there is much debate about the

value of occlusion therapy, this therapy is useful for many

children with specific types of amblyopia.

Orthoptic treatment

Occlusion of a child’s good eye to stimulate the amblyopic

A series of visual exercises may encourage the simultaneous

eye

use of both eyes.

Surgery

The ocular muscles can be repositioned to straighten the eyes.

Glasses are prescribed and occlusion performed before surgery,

because an eye is more likely to stay straight if the vision is

good. In adults “adjustable” surgery can be carried out. The

muscle position is adjusted by altering the tension on the

sutures postoperatively.

Botulinum toxin

Very small amounts of botulinum toxin can be injected into

Muscle

overacting muscles to paralyse them for a few months. The

moved

treatment can then be repeated. It can also permit the

back

assessment of the effect of prospective surgery before

permanent surgery is carried out.

Muscle

shortened

In the older child

The effectiveness of treatment in reversing amblyopia decreases

as the child gets older. Once the child is about 8 or 9 years old

Operation for squint

the visual system is no longer flexible and amblyopia cannot be

reversed. However, the child may still need glasses to correct

any refractive error, and an operation may be required if the

squint poses a cosmetic problem.

General medical disorders and the eye

Most serious medical conditions affect the eye. It is important

Systemic diseases with ocular manifestations

to know the ocular manifestations of systemic diseases for

●

Diabetes mellitus

several reasons.

●

Hypertension

●

Thyroid eye disease

●

Screening can detect early ocular changes that may require

●

Rheumatoid arthritis

treatment to prevent blindness. A good example is a diabetic

●

Seronegative arthritides

patient with new vessels on the optic disc, which signal an

●

Giant cell arteritis

exceptionally high risk of visual loss unless treatment is

●

Rosacea

given in time.

●

Sarcoid

●

Knowledge of the ocular complications of other diseases may help in

●

Behçet’s syndrome

the diagnosis of an ocular problem. A red, locally injected, and

●

Tuberculosis

●

Congenital rubella

tender eye in a patient with rheumatoid arthritis suggests

●

AIDS

scleritis, which may progress to perforation of the eye. Iritis

should be strongly considered in a young man with

ankylosing spondylitis who presents with a red eye.

●

Ocular symptoms may suggest the systemic disease (for example,

prominent eyes and lid lag in hyperthyroidism) or confirm it

(for example, the Kayser-Fleischer ring of copper in Wilson’s

disease).

●

Ocular signs may have prognostic value. For example,

if cottonwool spots occur in the eyes of an

otherwise asymptomatic patient with AIDS, the prognosis

may be poor.

Diabetes mellitus

Diabetes mellitus is the most common cause of blindness

Cataract in a diabetic patient

among people of working age in the Western world. Two per

cent of the diabetic population are blind, many of them in the

younger age groups. Much of this eye disease can be treated,

which makes early identification and referral crucial.

Cataract and primary open angle glaucoma are more

common in diabetic than in non-diabetic patients. Cataract

can be treated by surgical removal, and primary open angle

glaucoma can be treated by drugs and operations that lower

the intraocular pressure. Cataract can often be detected by

viewing the red reflex; glaucoma by examining the optic

disc. It is only too easy to forget to look for glaucomatous

cupping of the disc when looking for signs of diabetic

retinopathy.

Background retinopathy: hard

exudates, microaneurysms, and

Blinding diabetic retinopathy occurs in both insulin

haemorrhages

dependent and non-insulin dependent diabetic patients of all

ages. For all categories of patient, the longer the duration of

the diabetes, the more likely the patient is to have retinopathy

(about 80% are affected after 20 years). However, the better the

control of blood sugar levels, the lower the incidence of

diabetic retinopathy. To avoid missing important signs, diabetic

patients should have their fundi examined annually, by dilating

the pupils with tropicamide 1%.

Classification of diabetic retinopathy

The current classification of diabetic retinopathy was introduced by

the Early Treatment Diabetic Retinopathy Study (ETDRS):

●

Non-proliferative diabetic retinopathy (NPDR) mild, moderate,

and severe

Proliferative retinopathy: new

●

Proliferative diabetic retinopathy (PDR)

vessels, fibrosis, and haemorrhage

●

Diabetic maculopathy

ABC of Eyes

Non-proliferative diabetic retinopathy

This is typified by microaneurysms, dot haemorrhages, and

hard yellow exudates with well defined edges (called

background diabetic retinopathy in some classifications). These

changes do not have much effect on vision when they occur in

the peripheral retina. However, there is a spectrum of changes

in NPDR, some of which are associated with more ischaemic

damage. These changes were previously classified as

“pre-proliferative” retinopathy. The features of this more

Fluorescein angiogram

ischaemic moderate to severe NPDR are:

showing areas of leakage

●

Intraretinal microvascular abnormalities (IRMA)

●

Cottonwool spots

●

Deeper blotch and cluster haemorrhages

●

Venous dilatation, beading and looping.

NPDR may coexist with diabetic maculopathy. The more

ischaemic NPDR changes should alert the clinician to the

possibility of progression to blinding proliferative diabetic

Non-proliferative diabetic

retinopathy.

retinopathy with macular

changes and good vision:

Proliferative diabetic retinopathy

refer

Typified by the growth of new vessels on the retina or into the

vitreous cavity and thought to result from the ischaemic

diabetic retina producing vasoproliferative factors that cause

the growth of abnormal new vessels. These vessels may bleed,

causing a sudden decrease in vision because of a vitreous

haemorrhage. Worse still, this blood often results in the

production of contractile membranes that gradually pull off the

retina (tractional retinal detachment), causing blindness. This

may occur in any diabetic patient, but more commonly is seen

Proliferative retinopathy:

in young, insulin dependent patients. The vision may be 6/6

refer immediately

right up to the moment of a bleed, so early detection of new

vessels by adequate fundal examination is crucial. Fluorescein

angiography may help to identify areas of retinal ischaemia and

new vessel formation. New vessels may also grow at the front of

the eye on the iris and occlude the drainage angle of the

anterior chamber causing glaucoma (rubeotic glaucoma).

Laser treatment (or any other method of photocoagulation)

is used to treat proliferative retinopathy. The laser, however, is

not usually used to coagulate new vessels as these may bleed or

Diabetic vitreous

recur. When a patient has new vessels at the disc, the entire

haemorrhage

retina is treated with laser, except for the macula area, which

preserves the central vision. This treatment, often called

“panretinal photocoagulation” or “pattern bombing,” destroys

much of the ischaemic peripheral retina and stops it producing

the vasoproliferative factors that induce the growth of new

vessels, and often the new vessels regress. New blood vessels on

the iris that block the outflow of aqueous and cause rubeotic

glaucoma may also regress. However, thousands of laser burns

and repeated treatments may be needed to achieve this. This

treatment may substantially reduce peripheral vision and night

Diabetic retinopathy: recent

vision and means that the patient may have to give up driving.

and old laser burns

There is much current research in the development of

clinically applicable antagonists to the vasoproliferative growth

factors (for example, vascular endothelial growth factor

(VEGF) antagonists).

Diabetic maculopathy

Diabetic maculopathy may be divided into four types:

●

Focal exudative macular oedema

Measures to improve prognosis in diabetic

●

Diffuse exudative macular oedema

retinopathy

●

Ischaemic maculopathy

●

Control blood sugar

●

Mixed types.

●

Control hypertension

●

Control hyperlipidaemia

When diabetic retinopathy causes vessel leakage and ischaemia

●

Stop smoking

in the macula area, central vision may be severely affected.

General medical disorders and the eye

Diabetic maculopathy is the major cause of blindness in

maturity onset (Type 2) diabetes, but it also occurs in younger,

insulin dependent diabetics. It may be amenable to focal laser

photocoagulation, which may help to reduce any leakage,

particularly when hard exudates are a prominent feature of the

maculopathy.

Screening for diabetic eye disease

Patients may be divided into five groups for screening purposes.

Diabetic maculopathy

●

Patients with no retinopathy or with minimal non-

proliferative (background) retinopathy and normal vision

when tested with glasses or pinhole. These patients can be

reviewed yearly with dilation of the pupils. They should be

told to attend sooner if there is a change in vision that is not

corrected with glasses.

●

Patients with non-proliferative (background) retinopathy and

changes around the macula area. They should be referred to

an ophthalmologist, as this may herald a blinding

maculopathy.

●

Patients with non-proliferative (background) retinopathy and

Non-proliferative diabetic

retinopathy with good

impaired acuity not corrected with glasses or pinhole. The

acuity: review regularly

patient may have an oedematous or ischaemic form of

maculopathy that is extremely hard to diagnose with the

direct ophthalmoscope alone. The oedematous form may

respond to focal laser treatment if this is given early.

●

Patients with moderate to severe non-proliferative

(preproliferative) retinopathy. They have no new vessels, but

the haemorrhages are larger, the veins are tortuous, and

there are cottonwool spots. These signs imply that the retina

is ischaemic and that there is a high risk that new vessels will

subsequently form. These patients should be referred.

●

Patients with proliferative retinopathy. This is typified

Non-proliferative diabetic

retinopathy with reduced

by new blood vessels, and sometimes cottonwool spots,

acuity: refer

fibrosis, and vitreous haemorrhages. These patients need

immediate referral, particularly if there are vitreous

haemorrhages.

In addition to ocular treatment, blood sugar should be

carefully controlled. If the blood sugar concentration is

brought under control rapidly, the fundus should be reviewed

regularly during this period, as there may be a transient

worsening of the retinopathy. There is no question that good

control of the blood sugar level reduces diabetic retinopathy.

Severe non-proliferative

Hypertension, renal failure, and hyperlipidaemia worsen the

diabetic retinopathy

prognosis of retinopathy and must also be controlled. Patients

“Pre-proliferative”:

should be strongly advised not to smoke.

refer urgently

Diabetic patients are also more prone to recurrent corneal

abrasions, anteror uveitis, retinal vein occlusions, and cranial

nerve palsies.

Practical aids for diabetic patients with

impaired vision include an audible click

count syringe and a Hypotest instrument

Hypertension

that gives an audible signal with urinary

Diastix

The mild fundal changes of hypertension are extremely

common. “Silver wiring” of the retinal arteries and

arteriovenous nipping are well known signs, but arteriolar

narrowing is the most reliable fundal sign.

Accelerated (malignant) hypertension is classically

associated with swelling of the head of the optic nerve. Any

patient with hard exudates, cottonwool spots, or haemorrhages

as a result of hypertension has a grave prognosis. Patients with

these fundal signs should have their blood pressure checked

Retinopathy in accelerated

hypertension with

and diabetes excluded. Urgent referral to a physician is

macular exudates and

required as this combination of signs may not only result in

occluded vessels; disc

blindness but is also life threatening. Retinal vein occlusion is

swelling has resolved

also more common in hypertensive patients.

ABC of Eyes

Thyroid eye disease

Patients may have signs associated with hyperthyroidism and

the consequent overaction of the sympathetic system. These

patients have retracted upper and lower lids caused by excessive

stimulation of sympathetically innervated muscles in the

eyelids. This also gives rise to the well known sign of lid lag

when the patient looks downwards. These features may

suggest the diagnosis when the patient walks into the surgery.

If these signs are present, thyroid dysfunction should

be excluded. If there are no visual problems, no corneal

exposure, and the eyes move normally the patient need not

Hyperthyroidism with lid retraction

be referred.

Patients may also have evidence of autoimmune disease

directed against the orbital contents, particularly the muscles

and orbital fat (thyroid autoantibodies may be positive). These

signs may be associated with the classic signs of Graves’ disease,

including goitre, pseudoclubbing of the fingers (thyroid

acropathy), hyperthyroidism, and pretibial myxoedema.

Autoimmune orbital disease may also occur on its own with no

thyroid dysfunction and with normal thyroid autoantibody

status. The clinical features include the following, which may

occur in any combination.

●

Swelling of the eyelids

●

Oedema (chemosis) and engorgement of the blood vessels of the

conjunctiva

Autoimmune eye disease with restriction of ocular

●

Exposure of the cornea because of lack of blinking and failure of

movements

the lids to cover the eye adequately

●

Pronounced protrusion (exophthalmos) of the eyes. The absence of

this feature in association with the other features may be

even more serious, as a tight orbital septum may be holding

back the swollen orbital contents. This may lead to a rise in

intraocular pressure as well as pressure on the optic nerve

●

Restriction of eye movements. This is caused by infiltration of the

muscles with inflammatory cells, and consequent

inflammation, oedema, and finally fibrosis. These changes

can produce diplopia and strabismus

●

Optic neuropathy. This is relatively rare. The fundal signs

include vascular congestion and swelling or atrophy of the

Choroidal folds

head of the optic nerve. There may be “folds” in the choroid

caused by pressure on the globe. This should be excluded in

any patient with autoimmune eye disease who experiences

visual deterioration.

Management of thyroid eye disease

●

Associated thyroid dysfunction should be excluded, although

treatment of any dysfunction may make no difference to the

eye disease, and it may even make it worse

●

Patients should be strongly advised to stop smoking

●

Artificial tears and ointments should be used to lubricate the

cornea and prevent drying and corneal ulceration (especially

Radiology of thyroid eye disease

at night)

●

If there are cosmetic or exposure problems caused by lid

retraction, guanethidine 5% drops may reduce the lid

retraction by relaxing the sympathetically controlled retractor

muscles. Occasionally an operation on these muscles may be

required

●

If corneal exposure is threatening sight, the eyelids may have

to be sewn together temporarily or permanently

(tarsorrhaphy)

●

Prisms incorporated in the patient’s glasses may help to

correct any double vision

●

Operations on the muscles of eye movement may be required

to realign the eyes in patients with longstanding diplopia that

Patient with mild dysthyroid eye disease: red eyes and

has stabilised. Recently, the introduction of local injections of

exposure as a result of infrequent blinking

General medical disorders and the eye

minute doses of botulinum toxin to paralyse specific

In a patient with thyroid eye disease

extraocular muscles has meant that patients with restrictive

●

Protect cornea (exposure and ulceration)

muscle diseases may sometimes be treated at an earlier stage

●

Prevent damage to optic nerve (compression)

●

In serious disease with corneal problems or pressure on the

optic nerve, emergency treatment may be required, which

may include high doses of steroids, surgical orbital

compression, and radiotherapy. The visual fields may be

restricted and there may be a relative afferent pupillary

defect

●

Changes in colour vision, which may be noticed while

watching colour television, may be an important sign of optic

nerve compression, and patients should be told to inform

their doctor immediately if these changes are noticed

Rheumatoid arthritis

Ocular complications frequently occur in rheumatoid arthritis.

Dry eyes: Schirmer’s test

The lacrimal glands also are affected by an inflammatory

process with consequent inadequate tear flow. The patient

complains of dry, gritty, and sore eyes. Treatment consists of

replacement artificial tear drops instilled as often as necessary.

Simple ointment may also help, but this will blur the vision if

used during the day. If there is an aggregation of mucus,

mucolytic eye drops (for example, acetylcysteine) may help, but

patients should be warned that these sting. In a few patients the

“dry eye” syndrome may be sufficiently severe that there is

associated corneal melting.

The inflammatory process may also affect the episcleral and

scleral coats of the eye, causing the patient to complain of a

red, uncomfortable eye. The redness is usually focal and there

Episcleritis

is tenderness over the area.

Scleritis is usually much more painful than episcleritis and

the engorged vessels are deeper. If scleritis continues, the sclera

may become thin (scleromalacia) and the eye may eventually

perforate. The patient should be referred, as systemic

immunosuppression may be indicated.

These processes may also occur in other connective tissue

diseases such as systemic lupus erythematosus, scleroderma,

and dermatomyositis.

Seronegative arthritides

Scleritis

The seronegative arthritides include ankylosing spondylitis,

Reiter’s syndrome, psoriatic arthritis and arthritis associated

with inflammatory bowel disease. Acute anterior uveitis (iritis,

iridocyclitis) is much more common in these patients. If a

patient with any of these conditions has a red eye, anterior

uveitis should be suspected. This is particularly true if the

patient has had past attacks, and “experienced” patients often

know when an attack is coming on. The patient should be

referred for early treatment, which may prevent some of the

complications of anterior uveitis.

Seronegative childhood arthritis is a particularly important

Chronic anterior uveitis and

secondary cataract in

cause of chronic anterior uveitis. The great danger is that the

seronegative arthritis

eyes in this condition are often white and pain free, and the

child may not complain of any visual problems. There may be

secondary cataracts, which can cause irreversible amblyopia.

Glaucoma secondary to the anterior uveitis may also occur and

may be asymptomatic until the vision has been severely

Risk factors for ocular involvement in childhood

damaged.

seronegative arthritis

The group of children particularly at risk are girls,

●

Female sex

those with fewer than five joints affected by the arthritis

●

Fewer than five joints affected

(pauciarticular), and those with antinuclear antibodies in

●

Antinuclear antibodies

ABC of Eyes

their blood. These children should be referred to an

ophthalmologist.

Rosacea

Rosacea may seriously affect the eyes. There is often associated

severe blepharitis, which may result in recurrent chalazia and

styes. The abnormal lids and lipid secretion affect the tear film

and “dry eye” symptoms result. The cornea scars, particularly

in the inferonasal and inferotemporal areas, with

neovascularisation. Thinning occurs and occasionally the

Rosacea and associated blepharitis

cornea may perforate.

Treatment with tear substitutes is indicated together with

treatment for any associated blepharitis. Systemic tetracycline

(250 mg four times daily for up to a month, then daily for

several months) may considerably improve the patient’s ocular

as well as facial condition (avoid using tetracycline in pregnant

or lactating women).

Sarcoid

Sarcoid is associated with various ocular problems. Acute uveitis

and chronic uveitis occur, which may result in cataract,

Hypopyon uveitis

glaucoma, and a band of calcium deposited in the cornea

(band keratopathy). The lacrimal glands may be infiltrated,

resulting in “dry eye” symptoms that require tear replacement.

The granulomatous process may affect the posterior part of the

eye as vasculitis and sometimes infiltration of the optic nerve.

Congenital rubella

The ocular manifestations of congenital rubella are extremely

important. The child may have severe learning difficulties and

be deaf, so early recognition of ocular problems and their

Keratic precipitates

treatment are vital. The eyes are often microphthalmic and

associated treatable defects include cataract, glaucoma, squint,

and refractive errors. The cataract may not appear until several

Ocular manifestations of congenital rubella

weeks or months after birth, so the eyes should be re-examined.

There may be a diffuse retinopathy (“salt and pepper”

●

Cataract

●

Squint

appearance).

●

Refractive error

●

Glaucoma

●

Retinopathy

Acquired immune deficiency

syndrome (AIDS)

The ocular complications of AIDS can be blinding and include

retinitis, retinal detachment, papillitis, and cystoid macular

oedema. Manifestations of ocular human immunodeficiency

virus (HIV) infection include Kaposi’s sarcoma of the

conjunctiva and lids, HIV microvasculopathy (retinal

haemorrhages and cottonwool spots), and vasculitis. Ocular

cytomegalovirus (CMV) infection presents as a slowly

progressive necrotising retinitis with areas of retinal

opacification and haemorrhages and exudates along the

vascular arcades. About 20-30% of patients with CMV retinitis

will develop a retinal detachment.

Various antiviral agents have proved useful in the treatment

of ocular complications, but they may have to be taken

continuously, and systemic side effects from these treatments

are common. The use of agents such as ganciclovir, foscarnet,

Cytomegalovirus retinitis in AIDS

cidofovir, and more recently fomivirsen has proved to be very

effective in controlling CMV retinitis. Intraocular implants that

release local antiviral agents reduce systemic complications.

The eye and the nervous system

Nerves of eye movement

Ocular signs may be the first indication of serious neurological

disease. Alternatively, the eyes may be responsible for

Posterior communicating

Optic chiasm

artery

“neurological” symptoms such as headache.

Palsies of the third, fourth, and sixth cranial nerves all

cause paralytic squints, in which the angle of squint varies with

the direction of gaze. Adult patients may also complain of

double vision. It is important to exclude palsies of these three

Brain stem

nerves when examining patients who have a squint, double

vision, or both. In any patient with diplopia you should

consider the possibility of ocular myasthenia gravis, which can

mimic many different conditions.

Third nerve palsy

Patients with a third nerve palsy may present with a variety of

symptoms, depending on the cause of the palsy. These include

a drooping eyelid, double vision (if the lid does not cover the

eye), or headache in the distribution of the ophthalmic division

of the trigeminal nerve.

Aneurysm Internal carotid artery

Third nerve

On examination there is characteristically a ptosis (paralysed

levator muscle of the eyelid) and the eye is turned out because

Posterior communicating artery aneurysm compressing third nerve

of the action of the unaffected lateral rectus muscle that is

supplied by the sixth nerve. The eye is sometimes turned

slightly downwards because of the unopposed action of the

unaffected superior oblique muscle supplied by the fourth

nerve. The pupil is dilated if the parasympathetic fibres of the

third nerve supplying the sphincter pupillae have been

damaged.

Important causes of a third nerve palsy include intracranial

Aetiologies of third nerve palsy

aneurysms, compressive lesions in the cavernous sinus, diabetes

●

Aneurysm

mellitus, and trauma. If there is pain and a dilated pupil, a

●

Microvascular occlusion

compressive lesion must be excluded urgently, as life saving

●

Tumour

curative treatment may be needed for what could be a fatal

●

Trauma

lesion, such as an aneurysm.

Fourth nerve palsy

This is often difficult to diagnose. Patients may complain of a

combination of vertical and torsional diplopia, which may be

worse during activities such as walking down stairs or reading.

There may be a compensatory head tilt, with the head tilted

away from the side of the lesion and the chin depressed. The

fourth nerve is long and therefore is particularly susceptible to

injury. A patient with bilateral fourth nerve palsies following a

head injury may complain only of difficulty in reading.

This occurs as a result of difficulty during depression and

convergence of the eyes because both superior oblique

muscles are paralysed.

This diagnosis is easily missed if a careful history is not

taken, and it should be considered in any patient who

complains of difficulty in reading after a head injury.

Aetiologies of fourth nerve palsy

Fourth cranial nerve palsy—right hypertropia (see inferior scleral show) due

●

Congenital

to trauma. Signs are easily missed

●

Head trauma

●

Microvascular (including diabetes and

hypertension)

●

Tumour

●

Aneurysm

The eye and the nervous system

Sixth nerve palsy

A sixth nerve palsy may be the result of raised intracranial

This is probably the best known of the palsies of the three

pressure that is causing compression of the nerve

nerves of ocular motility. The eye on the affected side cannot

be abducted. The patient develops horizontal diplopia that

worsens when they look towards the side of the affected

muscle.

Aetiologies of sixth nerve palsy

Management of paralytic squint

● Tumour

A detailed ophthalmic, neurological, and general medical

● Microvascular occlusion

assessment is essential in order to make an accurate diagnosis.

● Trauma

● Aneurysm

If diplopia is a problem, opaque sticky tape may be placed over

● Raised intracranial pressure

the patient’s glasses or a patch may be placed over the eye.

Adults will not develop amblyopia. Temporary prisms can be

put on the glasses if the angle is not too large. For long term

treatment, permanent prisms (which are clearer than

Management of paralytic squint

temporary prisms) may be incorporated into a prescription for

● Diagnosis

glasses.

● Patch

Later, an operation may be performed to straighten the eyes.

● Temporary prism

Botulinum toxin may be injected into the extraocular muscles as

● Permanent prism

● Botulinum toxin

a diagnostic or therapeutic procedure in paralytic squint.

● Operation

Facial nerve palsy

Seventh nerve palsy

Facial weakness caused by a seventh nerve palsy is common

(called a Bell’s palsy). In many cases no cause is found and the

palsy improves spontaneously. If the eyelids do not close

properly, corneal exposure, ulceration, and eventually scarring

and blindness may occur. Ocular assessment should include the

following.

Testing of corneal sensation

The cornea is innervated by the ophthalmic branch of the

fifth nerve, which may also be affected by the pathology that

is causing the seventh nerve palsy. If the corneal sensation is

impaired, patients cannot feel foreign bodies or when their

corneas are ulcerating. They should be referred to an

ophthalmic surgeon, as there is a high risk of corneal

scarring. When the seventh nerve is affected the patient is

Right facial nerve palsy. The eyelids on the right have

unable to close the eye and there is inadequate lubrication

been partly sewn together to protect the eye

of the cornea.

Testing of Bell’s phenomenon

(Not to be confused with a Bell’s palsy.) Normally when the

eyes are closed the eyes move up under the upper lids. This

“Bell’s phenomenon” can be tested by observing the position of

the cornea while the patient closes their eyes. If the cornea

does not move up under the paralysed lid, the patient is at a

high risk of developing corneal exposure.

Staining the cornea with fluorescein

Staining of the cornea when fluorescein is used indicates that

the cornea is drying out. If there is only a tiny amount of stain,

the eye is white and unremarkable on external examination,

and the visual acuity is normal, the patient may be managed in

the short term with tear drops and ointment. If the staining

persists or if the eye becomes red then the patient should be

referred immediately to an ophthalmologist. The cornea may

need to be protected by frequent lubrication and by sewing

together the lateral parts of the eyelids or lowering the upper

Cornea moves up under upper lid on attempted

eyelid with botulinum toxin.

closure of the eye

ABC of Eyes

Seventh nerve palsy

The aim of treatment is to prevent corneal exposure and

●

Frequent ocular lubrication (day and night)

ulceration with subsequent complications of infection and

●

Eyelid taping to close lids (consider oval

perforation. Simple initial measures include frequent ocular

aciclovir and prednisone)

lubrication with artificial tears and ointments and lid taping to

●

Lateral tarsorrhaphy

physically close the eyelids. Recent studies have shown that

●

Gold weight insertion into upper lid

steroids are probably effective, and that the drug aciclovir

●

Nerve reconstructive surgery

combined with prednisone is possibly effective in improving

facial function. In more severe cases it may be necessary to

reduce the size of the palpebral aperture surgically by

performing a lateral tarsorrhaphy or by inserting an inert gold

weight into the upper eyelid. Nerve reconstructive surgery can

restore innervation to the facial muscles in severe cases.

Sympathetic pathway

Horner’s syndrome

In a patient with Horner’s syndrome the sympathetic nerve

supply to the eye is disturbed. The clinical features are as

follows.

● A small pupil that is reactive to light (unlike the small pupil

Horner’s

caused by pilocarpine eye drops) because the sympathetically

syndrome

innervated dilator muscle of the pupil is paralysed.

● A drooping eyelid. The muscles that raise the eyelid are

innervated by the third nerve and also by the sympathetic

nerve supply. Therefore lesions of either the third nerve or

Carotid aneurysm

the sympathetic nervous system supplying these muscles

(painful)

cause a ptosis, although in the latter case it is only slight.

● Lack of sweating on the same side of the face is because of

sympathetic denervation and depends on the position of the

lesion. The ocular movements are completely normal, as the

extraocular muscles are not sympathetically innervated.

Neck tumours

Brain stem

(syringobulbia)

Spinal cord

(syringomyelia)

Optic disc

Carcinoma of

The swollen optic disc

Sites of

apex of lung

There are many causes of a swollen optic disc, the best known

lesions of

the

of which is raised intracranial pressure resulting in the

sympathetic

development of papilloedema. The absence of papilloedema,

pathway to

however, does not exclude raised intracranial pressure. The

the eye

history and examination of the patient should lead to the

suspicion of raised intracranial pressure, and a swollen optic

disc is merely a helpful sign. The vision of patients with

papilloedema usually is not affected until late in the course of

the condition.

Most causes of a swollen disc are serious from either the

ocular or systemic point of view, and patients should be

referred promptly. If a patient has a swollen optic disc the

following features suggest a diagnosis other than raised

Papilloedema: swollen

intracranial pressure.

disc secondary to raised

intracranial pressure

Impaired vision

Vision usually is impaired only late in the course of

papilloedema. Impaired vision may indicate giant cell arteritis

and the patient may or may not have aching muscles, malaise,

headaches, tenderness over the temporal arteries, and

claudication of the jaw muscles when eating. The disc is

characteristically swollen and pale because the small vessels that

supply the head of the optic nerve are inflamed and occluded.

By this time vision will be severely affected. It is important to

exclude giant cell arteritis in any patient over 60 with visual

disturbance or a swollen optic disc, as urgent treatment with

Swollen disc secondary to temporal

steroids is needed to prevent blindness in the other eye.

arteritis

The eye and the nervous system

Disturbance of the visual fields

The visual fields of a patient with raised intracranial pressure

usually are normal. A field defect usually indicates some other

diagnosis, such as compression of the optic nerve.

Visual field: bitemporal hemianopia caused by pituitary adenoma

Computerised perimetry—homonymous quadrantanopia due to a stroke

A pale disc

The disc of a patient with raised intracranial pressure is often

hyperaemic. It is only in longstanding papilloedema that the

disc becomes atrophic and pale. The disc is also pale if the

swelling results from ischaemia of the optic nerve, as in giant

cell arteritis.

Retinal exudates and haemorrhages

These are present in papilloedema and are usually found

around the disc. If there are many exudates or haemorrhages

in the retina, diagnoses such as retinal vein occlusion,

malignant hypertension, diabetes, and vasculitis should be

considered. In all patients the blood pressure should be

measured and the urine tested for the presence of sugar, blood,

and protein.

Optic neuritis

ABC of Eyes

Conditions that may mimic swelling of the optic disc

●

Longsightedness (hypermetropia), in which the margin of

the optic disc does not look clear. A clue lies in the

patient’s glasses, which make the patient’s eyes look

larger.

●

Drusen of the head of the optic nerve—These colloid bodies of

the head of the nerve makes the margin of the disc look

blurred.

●

Developmental abnormalities of the head of the nerve—These may

Optic nerve head drusen

be difficult to diagnose.

Management

Patients with true papilloedema will need neurological

investigation. Patients with pseudopapilloedema and other

acquired causes of optic disc swelling (for example, retinal

venous occlusion, uveitis, optic neuritis, ischaemic optic

neuropathy, optic nerve compression, and optic nerve

tumours) will need full ophthalmic and neurological

examination and investigation.

Myelinated nerve fibres

The pale optic disc

There are many causes of a pale optic disc and it is vital to

make the correct diagnosis, as many of them are treatable.

These include compressive lesions, glaucoma, vitamin

deficiency, the presence of toxic substances (for example, lead

or some drugs), and infective conditions such as syphilis. It is

also important to identify whether the cause is hereditary, as

genetic counselling, and occasionally, metabolic treatments are

available (for example, a diet free of phytanic acid and plasma

Swollen disc secondary

to central retinal vein

exchange may prevent the progression of ocular disease in

occlusion

Refsum’s disease).

Aetiologies of the swollen optic disc

Headaches and the eye

Pseudopapilloedema

●

Optic disc drusen

Most patients who present with a history of “headache” around

●

Hypermetropia

the eye do not have serious disease. The following features in

●

Congenital anomaly of hyaloid system

the history and examination should raise suspicion of serious

Papilloedema

disease.

●

Blockage of ventricular system

●

Blockage of cerebrospinal fluid absorption

●

The nature of the headache—Headaches that cause sleep

●

Dural venous sinus thrombosis

disturbance or that are worse on waking or with coughing,

●

Space occupying lesion

suggest raised intracranial pressure. Temporal tenderness in

●

Hypersecretion by choroid plexus tumour

patients over the age of 60 with symptoms of aching muscles

●

Idiopathic (benign) intracranial hypertension

and malaise suggest giant cell arteritis.

Acquired swelling of the disc

●

Visual disturbance—If there is a change in visual acuity that

●

Eye disease—Retinal vein occlusion or uveitis

●

Vascular—Hypertension or ischaemic optic neuropathy

cannot be corrected by a pinhole test, serious disease

●

Inflammation—Optic neuritis

should be suspected. A history of haloes around lights

●

Drug related—Ethambutol, isoniazid, or streptomycin

(caused by transient oedema of the cornea when the

●

Infiltrative—Sarcoid, lymphoma, or leukaemia

intraocular pressure rises) suggests attacks of angle closure

●

Metabolic—Thyroid eye disease

glaucoma.

●

Compression—Optic nerve glioma or meningioma

●

A red eye—In acute glaucoma the eye is usually red, injected,

●

Disc tumour—Glioma or haemangioma, or metastatic

and tender, and the acuity is diminished. The pain is deep

seated and may be associated with vomiting. Inflammation of

the iris and ciliary body also cause a red eye and a deep pain.

Primary open angle glaucoma does not present with severe

pain.

●

Defective ocular movements—Restricted ocular movements on

“Headache” around the eye: important features

the same side as the pain may indicate serious disease,

●

Nature of pain

including orbital cellulitis (from infected sinuses),

●

Associated visual disturbance

inflammatory lesions in the orbit, and compressive lesions

●

Red eye

●

Defective ocular movements

causing nerve palsies (for example, a posterior

●

Abnormal pupils

communicating aneurysm causing third nerve palsy and pain

●

Abnormal optic disc

around the eye).

Global impact of eye disease

Impact of blindness worldwide

Every five seconds an adult goes blind somewhere in the world,

and every 60 seconds a child goes blind. Using the World

Health Organization (WHO) definition of blindness, defined as

vision in the better eye of less than 3/60, it is estimated that

there are about 45 million blind people in the world. There are

also about 135 million people who are visually impaired and

who need help.

Leading causes of blindness

worldwide

Ninety per cent of the world’s blind and visually impaired

people live in the countries of the developing world. The

Whole villages are affected by river blindness caused by Onchocerca volvulus.

impact of medical progress has been greatest in the more

Photograph reproduced with permission from the Christian Blind Mission

affluent countries of the developed world, where economic

resources have facilitated significant advances in tackling

blinding diseases.

Two hundred years ago the main cause of blindness in

Other* (24%)

western Europe was smallpox; 100 years ago this was replaced

Cataract (43%)

Onchocerciasis (1%)

by ophthalmia neonatorum. Although there are success stories

in the battle against blindness, it is important to remember that

blinding diseases still represent one of the major problems

facing developing nations.

Main causes of blindness in the

Vitamin A

deficiency (6%)

* Diabetic retinopathy,

developing world today

Trachoma (11%)

macular degeneration,

●

Cataract

Glaucoma (15%) optic neuropathy, etc

●

Glaucoma

●

Trachoma

●

Vitamin A deficiency

Pie chart of causes of world blindness

●

Onchocerciasis

Causes of blindness in the developing world

Cataract

About 20 million people are blind in both eyes because

of cataracts. These people could all be treated if they

had access to cataract surgery, and currently there are

Cataract

large scale programmes under way in many developing

countries.

Glaucoma

If glaucoma is detected at an early stage then blindness is

usually avoidable. However, long term topical glaucoma therapy

is not practicable in many low income countries, because of

cost, compliance, and access issues. Currently several research

programmes are evaluating the feasibility of surgery. In areas of

the world where angle closure glaucoma has a high prevalence,

laser therapy (peripheral iridotomy) has the potential to

Glaucoma—cupped disc

prevent much blinding disease.

Global impact of eye disease

Trachoma

Infection with Chlamydia trachomatis causes this severe scarring

conjunctival infection. Basic hygiene and public health

measures can dramatically reduce the prevalence of blinding

infection.

Severe trachomatous

scarring of tarsal

conjunctiva

Conjunctival infection with

Chlamydia trachomatis

Vitamin A deficiency

Chronic inflammation of

Vitamin A is needed to maintain epithelial surfaces (including

tarsal conjunctiva secondary

to chlamydial infection

the ocular surface) and to make retinal photoreceptor

pigments. Deficiency of vitamin A (xerophthalmia) causes

ocular surface dryness, scarring, infection with possible

perforation, and night blindness. Vitamin A supplementation

can eradicate this important blinding disease, which, coupled

with common childhood infections (such as measles), is a

major cause of blindness in children.

Corneal scarring caused by

vitamin A deficiency

Corneal melt after measles

in vitamin A deficient

patient

Endemic onchocerciasis

OCP treated area

Arabian

Peninsula

Africa

Onchocerciasis

0˚

“River blindness” is caused by the parasite Onchocerca volvulus,

carried by the blackfly, which transfers the parasite when it bites

humans. Infection results in corneal scarring, cataract,

Latin America

0˚

Areas affected by

glaucoma, and chorioretinitis. Treatment with ivermectin can

onchocerciasis

help control parasite levels in infected individuals, and public

health measures to eradicate the blackfly vector, which breeds

in fast flowing rivers, can reduce disease prevalence.

Corneal scarring caused by onchocerciasis

Onchocerciasis—blackfly vector

Onchocerciasis—parasite

ABC of Eyes

Main causes of blindness in developed countries

●

Age-related macular degeneration (ARMD)

●

Glaucoma

●

Cataract

●

Diabetic retinopathy

●

Refractive error

Age-related macular

degeneration

Glaucomatous cupping of

optic disc

Changing nature of blindness

Cataract

in “middle income” countries

Many South American and eastern European countries now fall

into this economic category. The extreme poverty common in

the developing world is not so prevalent in these countries, and

there are pockets of very high quality ophthalmic care. Two

ophthalmic diseases in particular have the potential to increase

dramatically in prevalence in “middle income” countries:

retinopathy of prematurity and diabetic retinopathy.

“Dragged” optic disc and

Retinopathy of prematurity (ROP)

macula due to peripheral

scarring and contraction of

The prevalence of blinding ROP is increasing in many “middle

retina

income” countries because basic neonatal intensive care

facilities are available. Although better neonatal care means

more babies survive, there are usually very limited facilities for

monitoring babies. As a result, many babies receive

unmonitored supplemental oxygen therapy and therefore are

at increased risk of developing severe ROP.

Diabetic retinopathy

As the levels of income, nutrition, and basic health care

increase, more patients with type 1 and type 2 diabetes will

survive into later life. Many of these patients will develop sight

threatening diabetic retinopathy, but there is simply not

enough access to laser treatment facilities to manage their

retinopathy and prevent blinding complications.

Cryotherapy for treatment of retinopathy

of prematurity being performed in

intensive care while baby continues to be

ventilated

New vessels on optic disc in

proliferative diabetic

Diabetic maculopathy

retinopathy

Global impact of eye disease

Eye disease in patients from outside

the United Kingdom

With modern air travel, the number of people travelling to the

United Kingdom from developing countries has increased

dramatically. An overseas patient with an ophthalmic problem

may have a tropical ophthalmic disease not usually seen in

the United Kingdom (for example, red eye due to trachoma)

or an ophthalmic manifestation of a systemic disease (for

example, red eye and uveitis secondary to tuberculosis).

Granulomatous uveitis—for example in

tuberculosis

Travelling outside the United Kingdom

Many patients will ask their family doctor for ophthalmic advice

before travelling. Some common questions are answered below.

Can I fly after surgery for retinal detachment?

Patients who have had gas injected inside their eyes to provide

tamponade as part of surgery for retinal detachment should

consult their ophthalmic surgeon before flying, as it usually

takes several weeks for the potentially expansile gas (sulphur

hexafluoride) to be absorbed postoperatively. Aircraft cabins

are usually pressurised (to about 8000 feet) during flight, which

can cause the intraocular gas to expand while the plane is in

the air, leading to acute glaucoma.

How soon after eye surgery can I go abroad?

Postoperative glaucoma drainage bleb

All patients who have had intraocular surgery (for example,

cataract surgery) are at risk of delayed complications such as

inflammation or infection for the first two to four weeks post

operatively. The patient should consult their ophthalmic

surgeon before arranging travel abroad.

Should I take any precautions because of my

eye problems?

●

Patients who are prone to recurrent uveitis or corneal herpetic

disease may experience a reactivation of their problem while

abroad. Patients should carry basic information about their

condition with them and may carry a supply of appropriate

medication in case of a flare up. It is always best to seek an

expert ophthalmic opinion before starting therapy abroad

●

Patients who have had previous glaucoma surgery may

benefit from carrying a supply of topical antibiotics in case

Contact lens related corneal abscess

they develop an infective conjunctivitis

●

Individuals that wear contact lenses should pay strict

attention to hygiene when using lenses in developing

countries. Non-sterile water (for example, from taps) used to

clean contact lenses or contact lens cases may be a source of

pathogens such as acanthamoeba, which can cause

intractable, potentially blinding infection. Care should be

taken with contact lens hygiene, especially if wearing contact

lenses on long haul flights. Daily wear contact lenses should

not be worn overnight on long flights, because the cabin

It is estimated that over the next

partial pressure of oxygen is reduced considerably

two decades the number of blind

●

Patients with “dry eye” syndromes may experience a marked

and visually impaired people in the

exacerbation of their symptoms in the dry atmosphere of the

world will double to 360 million

aircraft cabin and should carry a supply of ocular lubricants.

Summary

The global population is increasing and ageing rapidly. As

population demographics change, the prevalence of sight

threatening disease will also change. Global initiatives, such as

Vision 2020: “the right to sight,” which aim to eliminate

avoidable blindness by 2020, set us all a daunting challenge.

Index

Please note that page references in bold refer to figures and those in italics refer to tables/boxed material.

accommodation 15, 15, 17

arcuate scotoma 53

acetazolamide 55, 57

Argyll Robertson pupils 3

acetylcysteine eye drops 28

arterial pressure, venous occlusion and 37, 37

acne rosacea 22, 22, 74, 74

arteries

Action for Blind People 42

aneurysm, third nerve palsy 76

acute angle closure glaucoma 54-6, 55

occlusion 36, 36-7

cloudy cornea 52

arteritis

headache 80

giant cell 37, 78

management 55, 55-6, 56

temporal 37, 78

red eye 7, 12, 12

arthritides

risk factors 55

juvenile chronic arthritis 11, 73

symptoms/signs 12, 52, 55

rheumatoid arthritis 27, 73, 73

adenoviral infections 8, 14

seronegative 73-4, 73

age-related changes

Association for Blind Asians (ABA) 42

eye disease and 85

astigmatism 17, 17

lens (crystalline) 15

autoimmune eye disease 72, 72

macular see age-related macular degeneration (ARMD)

age-related macular degeneration (ARMD) 60-3

bacterial infections

clinical features 61

blindness in developing countries 82, 82

dry (atrophic, non-exudative) 60, 61, 61

conjunctivitis 7, 8, 8, 9, 9

epidemiology 60

contact lenses 18

investigation 61

basal cell carcinoma 4, 21, 22, 22

management 61-3, 63

Bell’s phenomenon, facial nerve palsy 77

ophthalmoscopy 6

Benefits Agency helpline 42

risk factors 60, 60

blockers, glaucoma management 56

visual loss

40, 60, 61

bimatoprost, glaucoma management 57

wet (exudative, neovascular) 60, 61, 61, 62-3

blackheads, eyelid infection 23

AIDS/HIV infection 74-5, 74

“blebs” 59, 59

Albinism Fellowship 42

blepharitis 4, 22, 22, 74, 74

allergies/hypersensitivity

blepharospasm 26

acute eyelid inflammation 23

blindness

conjunctivitis 9, 9-10, 14, 14

age-related macular degeneration 62

glaucoma drugs 57, 57-8

developed countries 84, 84

amaurosis fugax 39

developing countries 82, 82, 82-3, 83

amblyopia 65

global impact 82, 82

history 1

orbital cellulitis

ptosis and 25

organisations/addresses 42, 43, 44-5

squint and 65, 67, 67-8

registration 43