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Ageing of the eye: practical tips

In the first of eight articles covering comon eye complaints, Dr Scott Fraser discusses management of problems affecting older patients

While it is true that a number of conditions become more common with increasing age, visual failure is not inevitable. When a patient complains of problems with their sight, age is not a diagnosis, whether or not the cause is remediable.

A study of GP practices in London found one in four of the over-75s had some form of visual impairment. However, sight-altering conditions are not the only problems in the ageing eye.

Cataract

Age-related cataract is one of the commonest causes of reduced vision in the elderly and one that is readily amenable to treatment. There is a common misconception that the presence of a cataract is grounds for extraction, but some form of lens opacification can be seen from around age 40 and it is only when this becomes visually significant that surgery may be necessary.

So what does 'visually significant' mean? Generally speaking it is when the cataract is having an adverse effect on the person's lifestyle. This can vary from glare when driving for a 50-year-old salesman to problems seeing bus numbers for an

80-year-old. While cataract surgery is highly effective, a morbidity and small mortality are associated with it and, as in any operation, the intended benefits should outweigh the risks.

If you suspect a patient has cataract, a sight test is useful as:

lvision may be satisfactorily corrected by spectacles

lco-morbidity may be present

lit is useful for the ophthalmologist to whom you refer to have an idea of the patient's refraction.

Referral letters need not be detailed and can consist of:

lthe diagnosis and whether the patient wants surgery

lsignificant past medical history and medications

la copy of the optometrist's letter.

Age-related macular

degeneration (ARMD)

This used to be called senile macular degeneration, but for obvious reasons ARMD is a more preferable description. It represents a degeneration of the photoreceptors at the macula. In a small proportion of cases, choroidal blood vessels grow into this area — this is called 'wet' ARMD and is important as it is potentially treatable.

The 'dry' type is not uncommon and usually leads to increasing difficulties with small print; as it progresses many patients find difficulty recognising faces.

There is some evidence that disease progression can be slowed with vitamin supplementation, but as yet the optimal vitamins and doses are not known. Any patient with ARMD should be advised not to smoke and to ensure their diet is rich in vegetables and fruit.

Most ARMD is diagnosed initially by high-street optometrists. If the patient is symptomatic they often suggest referral for a number of reasons:

lconfirmation of the diagnosis with explanation

lexamination for treatable co-morbidity, eg cataract

laccess to low visual aids (LVAs) and social services.

The wet type of ARMD has recently gained prominence because of new treatments. It is important to realise this treatment is only to prevent further decline, rather than improve vision. Any patient with known ARMD needs to be warned that if they notice a sudden (days) decrease in vision or a distortion of straight lines (for example, looking at a door or window frame) they should attend their local eye casualty as soon as possible.

Glaucoma

The two major types of glaucoma – open angle and closed angle – have an increasing prevalence with age. Open angle glaucoma is asymptomatic and is therefore one of the major reasons people are advised to have biannual eye checks.

Acute closed angle glaucoma is symptomatic, with a painful reduction in vision. It can sometimes be picked up before the acute event allowing referral for prophylactic treatment.

Pupils

There is a normal age-related pupil miosis (reduction in size). This has little effect on the vision but can make viewing of the fundus difficult – especially if dilating drops are not used.

Presbyopia

Most people in their mid-40s will, because of the decreased ability of the natural lens to change shape, need glasses to read with. This tendency stabilises within a few years and most people's refraction remains reasonably stable after this unless other conditions intervene, such as cataract. Myopes (shortsighted people) can often manage without reading glasses into their 50s, while hypermetropes may need help in their early 40s or late 30s.

Eyelid tissue laxity

As elsewhere in the body, the tissues around the eye undergo involutional changes with age. This can lead to three main problems:

lptosis – drooping of the upper lid; if this is cosmetically a problem or interfering with vision, the patient needs to be referred for possible oculoplastic surgery

lentropion – in-turning of the lower lid resulting in the lashes rubbing on the cornea; referral is indicated for surgery; in the interim the patient can use tape on the lower lid to pull it down, turning the lid margin outward

lectropion – this is when the laxity causes the lid margin to turn outward so that the lid is not apposed to the globe; this often causes watering and if it is troublesome the patient should be referred.

The lacrimal system

The lacrimal gland can slowly reduce its production of tears with age. This is manifested as a chronically sore eye, often made worse in situations where blinking is reduced, such as when reading or watching TV. Simple tear substitutes are usually effective, such as hypromellose.

Conversely, the nasolacrimal duct can stenose over time, causing blockage and subsequent watering. If this is particularly troublesome or is resulting in repeated infections, surgery may be indicated.

Scott Fraser is consultant ophthalmologist at Sunderland Eye Infirmary and co-author of Eye Know How (BMJ Books, 2000)

Take-home points

lThose who do have a sight problem need to have a diagnosis

lThose over 40 should have a sight test every two years

lHypermetropes may need glasses in their

late 30s/early 40s but myopes can often manage without into their 50s

lLens opacification can be seen from age 40 but surgery is only needed when visually significant

lTreatment for 'wet' ARMD only prevents further decline in vision

lAge-related pupil miosis is normal

Further information

Ageing: A Global Perspective. Community Eye Health 1999;12(29): www.jceh.co.uk/download/

EYE29.PDF

Bandolier on cataracts: www.jr2.ox.ac.uk/bandolier/band27/

b27-6.html

eMedicine on ophthalmology: www.emedicine.com/oph/index.shtml

Hammond, C. The Ageing Eye: www.optometry.co.uk/articles/20030725/hammond20030725.pdf

NICE guidelines for ARMD: www.nice.org.uk/cat.asp?c=86772

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