Conditions that commonly cause blindness and visual impairment.
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Sight loss takes many forms

Visual impairment is a deeply personal experience and no two cases are the same. For example, while some people don’t see in the dark - others are badly affected by bright sunlight. Some have a restricted field of vision, whether peripherally, centrally or randomly. Two people with the same eye condition will cope in different ways. Sight varies - some days we see far better than on others.

How is visual impairment measured?

Partial sight can be hard to judge, as there are so many variables. Put simply, if you cannot read normal newsprint whilst wearing glasses or contact lenses then you could be considered partially sighted. Blindness and partial sight are formally defined terms which relate to the quality of vision. It is important to remember that most people described as blind can see something. Below we explain the commonest causes of visual impairment and blindness.

Macular Degeneration

This group of eye conditions causes damage to the retina and potential loss of central vision. Sight may initially appear distorted or there may be blank areas in the central field of vision. The macular, the part of the retina at the back of the eye which “sees” detail and colour, becomes damaged, sometimes referred to as “dry” or “wet” degeneration. The commonest type of macular degeneration (MD) occurs in people over 50 years of age accounting for over one third of all cases of visual impairment in the country. It is still largely untreatable, apart from a small proportion of specific types of the condition. Although MD is a very serious condition, the person affected will not go totally blind - peripheral vision is unaffected, and independence can be maintained with appropriate low vision aids, training and use of specialist equipment, issued by social services or available from OAB.

Glaucoma

The risk of glaucoma increases with age. It is usually associated with raised fluid pressure in the eye which damages the optic nerve. The commonest type of glaucoma can go unnoticed, as it generally results in loss of peripheral vision before central vision is affected and as such has been called “the silent thief of sight”. If untreated, it may cause blindness. in most cases there are several treatments available including drugs, eye drops, conventional and/or laser surgery available to halt progressive sight loss. Once diagnosed, regular eye examinations and good compliance with medication will help to prevent sight loss.

Cataract

Cataract, commonly associated with ageing, is a condition where the lens inside the eye becomes opaque. Cataracts can also be caused by trauma to the eye or by other eye conditions. Surgery can remove the opaque lens, which is usually replaced by a small plastic lens fitted inside the eye, known as an intra-ocular lens. This can be a fixed focus lens (either for close up work, such as reading, or for seeing distance) or a multi-focal lens for distance and close up vision. This treatment is usually very effective but spectacles may still be needed to give fine focus. If an implant is not appropriate, vision is corrected with glasses or contact lenses. If cataract occurs in the presence of other eye conditions, surgery may still be beneficial, so consult with a professional for advice.

Diabetic Retinopathy

This is more likely to affect people the longer they have been diagnosed with diabetes. It involves haemorrhaging of the vessels at the back of either or both eyes. The symptoms may include loss of field of vision, poor focus and loss of detail vision, becoming more pronounced as the condition progresses. Laser treatment can halt vision loss and prevent further damage. The most effective way to prevent further sight loss is by maintaining good control of the diabetes. Therefore, it is very important that people with this condition remain under regular review and seek medical advice on any further visual symptoms which may present themselves. Your optometrist can check for this.

A few words

Since three of the four conditions leading to visual impairment are treatable, they ought not to be amongst the major causes of partial sight and blindness. Early detection of most eye conditions leading to visual impairment increases the possibility of effective treatment, although, in most cases, it is only possible to prevent progression of further sight loss rather than to restore vision to its former level. Eye examinations at two yearly intervals are therefore advisable for every one. More frequent examinations may be required where pathology is present or where there is an increased risk of an eye condition indicated by family history.

You only have to ask

For further information about these eye conditions or indeed any matter related to visual impairment contact David Thompson at Oxfordshire Association for the Blind.