Q I heard that estrogen-replacement therapy isn't effective in preventing heart attacks in women. Is this true? J.E., Tucson

A Many studies have proven that estrogen-replacement therapy significantly decreases the incidence of cardiovascular disease in postmenopausal women. Hormone-replacement therapy is effective and is recommended except for women who have a family history of breast cancer. Starting estrogen-replacement therapy in women who have no evidence of heart disease is called primary prevention.

A study published in the Journal of the American Medical Association this past summer raised questions about the effectiveness of estrogen-replacement therapy in warding off heart trouble in older women. In this study, estrogen was begun in women who already had heart disease. This is called secondary prevention.

The results of this study apply only to women with existing heart disease who have been on estrogen-replacement therapy for less than one year. The study found an increased risk of blood clots and gall bladder disease.

Women who currently are taking estrogen-replacement therapy should continue to do so. The small group of women who have had a heart attack, bypass surgery or angioplasty, and who have been on the hormones for less than one year, should consult with their physician—although it is not an emergency.

However, when estrogen-replacement therapy is considered, the patient probably be screened for increased risk of clotting.

—Gordon A. Ewy, M.D., director, The University of Arizona Sarver Heart Center, Tucson

Q Is it true that taking one aspirin every day can help a person who has coronary artery disease or a history of stroke? M.G., Tucson

A Yes, it's true. Aspirin can help prevent strokes in thousands of people in the United States every year, according to scientific studies conducted since the early 1970s.

Considering the minimal side effects of aspirin, I recommend 325 mg of aspirin every other day. Before you start taking aspirin on a regular basis, however, check with your physician to see what's right for you.

—James E. Dalen, M.D., M.P.H., vice president for health sciences and dean, The University of Arizona College of Medicine, Tucson.

(EDITORS NOTE: February is Low Vision Awareness Month)

Q What is macular degeneration? How common is it, how is it diagnosed and treated? A.H., Tucson

A Macular degeneration is an eye disease that impairs vision by gradually destroying the sharp, central vision needed for seeing objects clearly and for common daily activities such as reading and driving.

It is the most common cause of impaired vision in people over the age of 50. Studies show that people over age 60 are at greater risk. People over age 75 have a nearly 30 percent risk.

Others at risk include those who have an immediate family member who has the disease and those who smoke or who are exposed to second-hand smoke. Women tend to be at greater risk than men.

Symptoms include blurred vision that goes away in brighter light, straight lines that appear wavy, or a small but growing blind spot in the middle of the field of vision.

Macular degeneration occurs in two forms: wet or dry. The dry form, the more common of the two, is caused by aging and thinning of the tissues of the macula, the small area at the back of the eye that allows us to see fine details clearly. The dry form develops slowly and may cause progressive loss of vision.

In the wet form, new blood vessels grow beneath the retina, leaking fluid and blood and creating a blind spot in the center of the visual field. Although about 10 percent of people with macular degeneration have the wet form, it accounts for 90 percent of all blindness from the disease.

Macular degeneration can be detected during an eye exam. Although there is no cure for macular degeneration, early detection is important because in some cases it allows for early treatment that may delay or reduce the severity of the disease.

Preliminary studies suggest that antioxidant vitamins and minerals may slow the progress of dry macular degeneration. If you have dry macular degeneration and are 60 years or older you should have your eyes examined once a year.

Some cases of wet macular degeneration can be treated with laser surgery. It is crucial for individuals with the wet form to have laser surgery before the disease destroys central vision.

—Richard R. Ober, M.D., professor, clinical opthalmology, Department of Opthalmology, The University of Arizona College of Medicine, Tucson