AMD

AMD is a condition that affects the macula within the eye, the most sensitive portion of the retina which is responsible for central and fine vision. The cause of AMD is unknown. There are two types of AMD: non-neovascular and neovascular. Although it produces visible abnormalities in the retina, non-neovascular AMD rarely leads to symptoms or loss of vision. By contrast, neovascular AMD is the leading cause of severe and irreversible loss of central vision in people over the age of 40 in the United States, with an estimated 1.2 million people affected. Let's look at this condition and see how it can be prevented and treated.

Symptoms of AMD

People with neovascular AMD can rather rapidly develop a hazy grayness or blank spot in their central vision. Reading becomes difficult or impossible due to blurring of words on paper and color vision may be dimmed or lost.

Prevention of AMD

Research presented about 10 years ago showed that high doses of a mixture of zinc and the antioxidants vitamins C and E and beta-carotene slowed the progression of AMD by 25 percent, but only in those who already had intermediate AMD or advanced disease in only one eye. This cocktail is still used in such people unless they are smokers. Beta-carotene supplements are avoided in smokers because they may increase the risk of lung cancer.

Promising ongoing studies are examining the possible preventive benefits of supplements containing omega-3 fatty acids or the antioxidant carotenoids, lutein and zeaxanthin, which are both present in the macula.

In addition, some studies suggest that AMD may be prevented by not smoking, controlling blood pressure and cholesterol levels, limiting intake of saturated fats, and avoiding exposure to sunlight.

Treatment of AMD

Photocoagulation of blood vessels with a laser decreases the risk of vision loss when new blood vessels can be identified growing in the area surrounding the macula. People must be followed closely following this procedure because there is a high rate of recurrence. But the procedure is risky because photocoagulation of vessels too close to the macula can damage the macula and result in a permanent blind spot in the central vision.

Because of this, photodynamic therapy has largely replaced photocoagulation for new blood vessel growth directly under the fovea, the most light-sensitive portion of the macula at its center. The undesirable new blood vessels are closed in a two step procedure: injection of a light sensitive drug which selectively binds to cells on new vessels is followed by delivery of a beam of low powered laser to the eye in order to activate the drug bound to the abnormal blood vessels.

Drugs that block new blood vessel growth

Three drugs for the treatment of AMD act by inhibiting the action of vascular endothelial growth factor (VEGF). The first medication approved by the FDA in 2004 is pegaptanib (Macugen); it is a nucleic acid that binds specifically to VEGF in the eye. In 2006 the FDA approved an antibody, ranibizumab (Lucentis), that binds to VEGF and blocks its action. Another antibody bevacizumab (Avastin), approved for treatment of colon and rectal cancer, has been used successfully off-label to treat AMD. All three of these drugs are injected directly into the eye and have been used for two years or longer. Lucentis and Avastin are now the most effective and standard treatments for AMD. A recent study showed they were equally effective when injected on a regular monthly schedule or as needed based on a monthly examination. However, costs may be a problem--each dose of Lucentis along with the procedure costs between $2,300 and $3,500.