garcia
Found this on Susan Clark's site (whatreallyworks.co.uk). I can't verify how kosher it is, but it certainly seems to suggest that diet may be a factor in controlling the disease.
Retinitis Pigmentosa
Retinitis pigmentosa (RP) is a rare inherited disorder (said to affect one in every 3,700 people) in which the retina - the light-sensitive membrane on the inner surface of the back of the eye - slowly and progressively degenerates, eventually causing blindness. The verdict with orthodox medicine is that there is no treatment and nothing you can do to stop this degeneration. Complementary medicine says otherwise.
Dr Eliot Berson, professor of ophthalmology at Harvard medical school, believes high doses of vitamin A can slow the loss of remaining eyesight by about 20% a year. He has been investigating the influence of vitamin A on the retina for 12 years and has extensive research, including papers in the American Journal of Clinical Nutrition, which show that the high doses he recommends are entirely safe. He is adamant that retinitis pigmentosa is treatable - and that if you take 15,000iu (international units) of vitamin A per day, you can prolong your eyesight for up to 10 years, as long as you are not taking vitamin E simultaneously which, he says, works adversely to lower the amount of A in the body.
Natural sources of pure vitamin A include liver and milk (if you eat carrots, the vitamin A in the form of carotene will not be used by the eye). Berson, who developed his theory after studying patient questionnaires which showed that those RP sufferers who were taking vitamin A in high doses preserved their vision for longer, says: “My research shows the treatment for this condition is painfully simple, effective and safe.”
http://www.whatreallyworks.co.uk/start/factsheets.asp?article_ID=510