Q: My uncle married his cousin and they have two children, a daughter and a son. Both my cousins have eye related problems and can't see at night and wear very powerful glasses. I have heard of consanguineous marriages causing problems to children. Both of them are married and have children. Now their children are having similar eye problems. They have to undergo surgery every year. Is there a permanent cure for vision problems associated with the children of such marriages? My cousins are brilliant students, but they get severe eye problems during exams due to which they are not able to take up exams. Can they undergo an eye operation to get new eye? What are the chances of them seeing normally? What is the solution to the problem?

A:What you have described, and I assume you are from South India, is a relatively common ailment called Retinitis pigmentosa. It runs in the family where there are consanguineous marriages, that is marriages between blood relatives. This condition causes deteriorating changes in the retina causing night blindness, followed by constriction of the field of vision and finally drop in central and reading vision, though it takes decades for this to happen. There is a very effective way of preventing this condition, and that is to completely avoid marriages within blood relations. As for treatment, only a very small subgroup of patients benefit by taking vitamin A. Research is on at Sankara Nethralaya, Chennai, to find the genes for this condition and hence a way to stop deterioration. There is no surgery to replace the entire eyeball. The only part of the eye which can be transplanted from a donor eye is the cornea, which is not affected in this condition.