DEAR DR. DONOHUE: I have progressive dry macular degeneration. Please let me know what the latest technique to prevent blindness is. — N.F.

ANSWER: Macular degeneration is one of the leading causes of adult blindness. The macula is a small area of the retina and its most sensitive area. It provides clear central vision, the kind needed for reading, driving and watching TV. Two varieties of macular degeneration exist. One is wet macular degeneration. It’s due to the proliferation of fragile blood vessels below the macula that leak fluid. It can progress rapidly. There are a greater number of treatments for wet macular degeneration than there are for the dry kind. That variety progresses more slowly and accounts for about 90 percent of all macular degeneration. With it, macular cells break down for reasons that are somewhat obscure.

Aging is one of the greatest contributory causes to macular degeneration. Smoking is another factor.

Macular degeneration doesn’t leave a person completely blind. Off-to-the side vision — peripheral vision — remains intact.

A well-known study called AREDS (Age-Related Eye Disease Study) found that the combination of vitamin C (500 mg), vitamin E (400 IU), beta carotene (15 mg), zinc oxide (80 mg) and copper (2 mg) slowed the progression of moderate macular degeneration to a more advanced stage. AREDS-2 is a new study still in progress. It’s a mixture of vitamins and minerals without beta carotene but with lutein and zeaxanthin in its place. It also includes omega-3 fatty acids in the mix.

Two products containing the AREDS-1 mixture in one tablet are Ocuvite Preser Vision and I-Caps AREDS Formula. Bausch and Lomb has marketed the AREDS-2 combination in one tablet before the study has been completed.

DEAR DR. DONOHUE: G.B. writes that her sister has irritable bowel syndrome. You stated, “All other illnesses with similar symptoms have to be considered.”

You are so right. Our daughter, at age 32, told her doctor about the same symptoms that G.B. had. He, too, said she had irritable bowel syndrome and continued to tell her at yearly intervals. At the age of 40, she had a brain tumor. It turns out the brain tumor was a metastasis that came from the colon. Her entire colon was full of cancer. She had been told to take Metamucil for her symptoms.

Doctors and patients learn from such experiences. — M.S.

ANSWER: My sincerest sympathy on the loss of your daughter.

I understand how the doctor would have persisted in the diagnosis of irritable bowel syndrome in such a young woman. Colon cancer isn’t common at her age. The story is upsetting to everyone — doctor and patients. It’s also instructive to all of us — doctors and patients. I wish I had words that could ease your grief.

DEAR DR. DONOHUE: Since cereals and foods have all the vitamins we need, what’s the reason why so many people insist on taking a daily multivitamin?

My wife is one of those people. Try as I do to discourage her, she refuses to listen to me. She says it provides her with assurance that she is meeting all the daily requirements. — A.J.

ANSWER: A varied diet does provide us with all the vitamins and minerals we need. And many foods and beverages are fortified with vitamins that are hard to come by through foods alone. It is best if we can get all those nutrients in foods. They’re better absorbed that way.

Many older people, however, do not eat the variety of foods that satisfy the minimal daily requirements. I understand how a multivitamin is useful for them.

A good investment is a paperback book that provides information on our daily needs of vitamins and minerals and has a list of the richest sources of those nutrients.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.