Q: My daughter is very, very angry with me. She blames me for her son's eye problem, X-linked retinoschisis. Am I really the culprit? How did I give it to him?

A: Your daughter is not being fair, and she misunderstands genetic illnesses.

X-linked retinoschisis (RET-uh-KNOWS-kuh-siss) is a gene defect found on the X chromosome. Chromosomes are long strands of genes. We have 23 chromosome pairs. The X and Y chromosomes determine a person's gender. Women have two X chromosomes, and men have an X and a Y chromosome.

The defective gene for this illness lies on the X chromosome. Since women have two of these chromosomes, the good chromosome blocks the action of the defective gene on the second X chromosome. Men, with only one X chromosome, have no second X chromosome to block the defective gene. Therefore, this illness is almost always a male illness.

"Schisis" means "splitting." With retinoschisis, the retina splits. The retina is the light-sensitive layer at the back of the eye. Retinoschisis affects vision, but the degree of visual damage varies greatly. You have the gene. You apparently have no vision problem. You gave the gene to your daughter. Your daughter, in turn, gave it to her son. She is a carrier of the gene. She has no vision problems, but half her sons can get the defective gene. That is not her fault, nor is it your fault.

You and your daughter can obtain more information on this illness by contacting The Foundation Fighting Blindness. Its toll-free number is (800) 683-5555, and its Web site is www.blindness.org. The foundation is dedicated to disseminating information and helping all those with visual impairment.

Q: I have a grandson who suffers from migraines. He is only 21. You wrote about this some time back and mentioned a medicine that could prevent these headaches. Would you mention it again?

Before resorting to medicines, your grandson must carefully rehash what happens in the 24 hours prior to his having a headache. He might find a trigger that he can eliminate.

If his headaches come often, preventive medicines should be considered. They don't stop a headache once it has started. They can ward them off. Inderal and Blocadren are two that work.