Retinitis pigmentosa (RP) is a group of rare hereditary disorders whose common feature is a gradual deterioration of the light sensitive cells of the retina. The name retinitis pigmentosa was applied by a doctor Donders in 1857. With hindsight it is not a good name; if discovered now, the condition would probably have been named "retinal dystrophies".
The symptoms of this group of disorders usually become apparent between the ages of 10 and 30, although some changes may become apparent in childhood. In one type of RP, Leber's Amaurosis, children may become blind – or almost so – within the first six months of life. By contrast, some types of RP may only show symptoms late in life.
In the more common types of RP, a person will have a history of visual problems at dusk or in poor light, so-called night blindness and a gradual reduction in the field of vision, loss of the outer edges, resulting in a tendency to trip over things.
The first reaction for many is to go for an eye test believing that they need glasses. Although glasses do a marvellous job correcting problems with the eye's lens, they cannot help a deteriorating retina. As the outer fringes of the field of vision gradually disappear, the RP sufferer is left with the condition commonly referred to as tunnel vision. Many people retain this tunnel of useful vision until quite late in life. The speed of loss of vision varies considerably from person to person, due to the many forms of RP.
As these cells slowly degenerate, people with RP develop night blindness and a gradual loss of peripheral vision. By about age 40, most have tunnel vision, although many may retain good central vision. Between the ages of 50 and 80, however, they typically lose their remaining sight. The extent of vision loss in people of the same age with RP may be different.
In one category of RP, the loss of vision begins in the central area. This is referred to as macular dystrophy (because the central macular area is affected). It causes an inability to read or carry out other work involving detail, although the person may have few mobility problems for several years.
In some cases RP is first diagnosed following a road accident.
There is no treatment for retinitis pigmentosa, although some practitioners believe that vitamin A may slightly delay vision loss. Occupational therapy may be wise before much of vision is lost. It may be easier to learn how to work around vision loss while vision is still available.
Retinitis pigmentosa results in visual rods being destroyed early in the course of disease, resulting in night blindness. Night blindness in children may be an early indicator of retinitis pigmentosa.
Some practitioners believe that vitamin A may slightly delay vision loss. According to a study reported in the Archives of Ophthalmology on June 14, 1993, most adults with blinding retinitis pigmentosa should take a daily 15,000 IU vitamin A supplement, based on results from this large, randomized clinical trial.
Eliot L. Berson, MD, the study's principal investigator and Professor of Ophthalmology at Harvard Medical School, said that adults who supplemented their diets with 15,000 IU of vitamin A daily had on average about a 20% slower annual decline of remaining retinal function than those not taking this dose.
Based on this finding, Dr. Berson and his colleagues estimated that an average patient in the study who started taking a 15,000 IU vitamin A capsule at age 32 would retain some useful vision until age 70, whereas a patient not on this dose would lose useful vision by age 63.
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