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Tracking a Vision Thief

Science still searches for the cause of sight-robbing AMD.
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WebMD Feature

At first, the only clue might be slightly distorted or blurry vision, or difficulty reading. When it gets worse, you decide to see your eye doctor.

In doing so, you might learn you have a condition called age-related macular degeneration, or AMD. In AMD, the macula -- the area of the retina that is responsible for your sharpest central vision -- deteriorates.

According to the National Eye Institute (NEI), one million people have AMD, the leading cause of blindness in people over the age of 60. Every year, 200,000 new cases are reported -- a number expected to increase as the baby boomer population ages.

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In "dry" AMD, the tissues of the retina thin and the cells of the macula "drop out." If this progresses enough, the resulting washed-out appearance of objects can make fine details on items, such as the letters on street signs, difficult to make out. Distortions or warping of images can also occur.

About 10% of patients have the "wet" form of the disease, in which abnormal blood vessels develop in the layer of tissue under the retina and leak blood and fluid, usually causing scar tissue, which creates a central blind spot. This more aggressive version of AMD accounts for about 90% of severe vision loss from the disease, according to the NEI.

There is no proven treatment for dry AMD. Other than advising people to avoid cigarette smoking and bright sunlight -- both considered risk factors -- and to watch their overall health, there's not much doctors can suggest.

Laser surgery can sometimes help those with the wet form. However, whether treatment is successful depends for the most part on how close the abnormal blood vessels are to the center of vision. (That's because the laser is used to cauterize, but in the process it destroys the overlying retina.) Under study is a new approach that uses a low-energy laser and light-activated medication.

"The message is, you have to live with this until we figure out what to do," says Lylas Mogk, M.D., an ophthalmologist with the Henry Ford Health System in Grosse Point, Michigan, who has written a book on the topic.

Fortunately, Mogk says, those who are "hard of seeing" can be taught to rely on magnification and better use of their peripheral vision. "There's an enormous amount of vision remaining," she says.

Searching for a Cause and a Cure

Scientists are working to better understand the disease in the hope of discovering ways to prevent and better treat it.

Eating modified dietary fats, such as partially hydrogenated vegetable oil, along with exposure to environmental pollution such as cigarette smoke may play a role, Mogk believes. "We are seeing the first generation [of those] who have lived their whole lives since we've been pumping the environment full of chemicals," Mogk says.

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