Q. In your answer about night blindness, you discussed tunnel vision. My problem is just the opposite -- I see fine to the sides but not very well straight ahead. My eye doctor says I have something called macular degeneration. I don't quite understand this condition.

Reading and driving are very important to me. I can do both now but am worried my vision will deteriorate. I am 73.

A. Even though macular degeneration (MD) is one of the leading causes of failing vision, most people are not very familiar with this condition. MD causes loss of central vision -- the area you focus on when looking directly at something.

The macula is the dot-sized part of the retina -- the nerves of vision in back of the eye -- responsible for sharp central vision. Macular degeneration refers to a breakdown or deterioration of this critical part of sight.

The most common form of macular degeneration occurs in older people and seems to be the result of aging changes inside the eye. Scientists aren't sure what causes it or why it affects some older people and not others.

In other cases, MD is associated with various disorders such as diabetes and atherosclerosis (hardening of the arteries), eye injury or excessive exposure to ultraviolet light rays. Rarely, MD occurs in a hereditary form and shows up at an early age, striking children and adolescents. MD is more common in people who are nearsighted.

The symptoms of MD develop gradually. Printing looks blurred, vertical lines are distorted, scenes appear smaller at the center than at the edges and there may be a dark spot at the point of focus.

Many other eye diseases, most notably cataracts, interfere with central vision. Anyone with loss of vision needing more than just a change in prescription should be checked by an ophthalmologist to determine its cause.

Unfortunately, there is no effective treatment for most cases of macular degeneration. In a few instances laser therapy, which destroys damaged blood vessels in the macular area, prevents further loss of sight. Other treatments have been tried, such as vitamins, various medicines and low-fat diets, but none has proved successful.

Even in severe cases of MD, an affected person can continue many routine activities, although those that require good central vision, such as reading and driving, may be impaired. It's difficult to predict the course of MD in a given individual, but if your vision becomes much worse, I suggest asking your eye doctor about low-vision aids.

For a helpful brochure that includes a home vision test for macular degeneration and for information about low-vision aids, contact the local chapter of the Prevention of Blindness Society, 1775 Church St. NW, Washington, D.C. 20036.

Q. I had a severe reaction to a bee sting years ago, and am now deathly afraid of stinging insects. What can I do to prevent a bad reaction from happening again?

A. Each year, bites from stinging insects kill twice as many people in the United States as bites from poisonous snakes. The stinging insects that share in this threat include bees, wasps, hornets, yellow jackets and fire ants.

About 10 to 15 percent of Americans are allergic to stinging insects. An allergic reaction is much different from the typical pain, local swelling and redness that follows an insect sting. Allergic, or hypersensitive, reactions cause severe local symptoms, as well as something called anaphylaxis, a potentially life threatening condition.

Anaphylaxis -- meaning "without protection" -- can trigger hives, nausea, stomach cramps, wheezing, difficulty breathing, swelling of the face and throat, shock, coma and death. Symptoms usually start minutes after a sting, so prompt treatment is critical. People at highest risk of anaphylaxis from a sting are those who have had severe hives, difficulty breathing or other serious reaction from a previous sting.

To reduce your chances of getting stung, avoid contact with stinging insects, wear shoes when outside, and don't wear fragrances or bright clothing which may attract them.

You have two ways to prevent a severe reaction from happening again. The first is immune therapy, or allergy shots using small doses of venom from stinging insects. These stimulate your immune system to develop antibodies that blunt your response to a sting.

The second is immediate treatment after a sting, using an emergency medical kit designed for this purpose. The kits all contain an injection of adrenalin (epinephrine), which stimulates your ability to fight a serious reaction. Some also have a tourniquet to dampen the flow of venom from an extremity into the rest of your bloodstream, and antihistamine tablets, which offset the body's normal response to a sting.

These kits are available by prescription only. Two brand names are Ana-Kit Insect Sting Treatment Kit and EpiPen Auto-Injector. I recommend asking your doctor about these and making sure you know how to inject yourself when needed.

Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington. Send questions to Consultation, Health Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Questions cannot be answered individually.