Loss of vision in the ageing eye

Age and Ageing, March, 1997 by A.J. Bron

As a diagnostic method, direct ophthalmoscopy has its limitations, and the patient's recognition of distortions while viewing the Amsler grid (Figure 1) is very informative. Angiography with fluorescein or indocyanin green will show up subretinal vessels, while electrodiagnostic methods may also be of value, particularly in inherited disease.

[Figure 1 ILLUSTRATION OMITTED]

Positive treatment is only possible in 5-10% of cases, when lasers can destroy subretinal vessels without damaging the central macula. Many medical therapies have been tried, but none have stood the test of controlled clinical trials, and the field is divided between charlatans and scientists. Optical aids and visual rehabilitation are of great value (see below).

For the future, what is needed is the use of epidemiological methods to elucidate risk factors, and of laboratory methods to study the mechanisms involved. Animal models are not perfect, and use must be made of donor eyes obtained post-mortem. Better coordination between interested centres is needed.

In discussion, the role of micronutrients was raised. Anti-oxidants are of no proven value, and the recent claim that dietary spinach is of use in prevention, but not in treatment, has little to substantiate it.

The functional effects of visual loss

Dr Parul Desai (Health Service Research Unit, Department of Public Health and Policy, The London School of Hygiene and Tropical Medicine) reported that visual loss and its effect on function has centred almost entirely around VA. Consideration of visual function is usually made once disease is established, or when comparisons are made before and after treatment. Little is known about premorbid visual function and how visual impairment affects function in the community. She urged greater precision in the use of the terms impairment (loss of function), disability (its effect on our activities), and handicap (its effect on social performance).

Self-reported visual disability in the community rises from 8% of those aged 65-74 to 24% of those over 75. However only half of those with self-reported disability actually met World Health Organisation criteria for visual impairment (VA less than 6/18 and more than 3/60), when their VA was measured. Four percent of those who did not report any visual problems met these WHO criteria; they thus had a clinically defined `need', which they themselves had not recognized or identified.

Although a subjective perception of visual decline in later life may compromise emotional well-being and functional status of elderly people, this population is not more likely to make greater use of formal health and social services than elderly people whose vision was good. Old people who are visually impaired also have poorer social contacts and physical function than blind people, and would appear to represent an under-served group within the elderly population [11, 12].

The management of blindness and partial sight

Miss Janet Silver (Principal Optometrist, Visual Assessment Department, Moorfields Eye Hospital, London) stressed that `no cure does not mean no help', and that the main consequences of `blindness' are a loss of independence for correspondence, newsprint, prices in shops, medication, and kitchen controls, and a humiliating loss of privacy in reading bills and bank statements. There is often a reaction very similar to bereavement, with denial, anger, and depression. She stressed the prevalence of myths which needed to be dispelled, that blindness is some sort of retribution, and that vision can be used up or worsened by its use.