Researchers have discovered the first effective treatment for age-related macular degeneration, the leading cause of blindness in people older than 50.
Until now, there has been no effective therapy for the disorder, which affects at least 6 million Americans and causes visual impairment in nearly a third of them. But a study of more than 3,600 patients conducted by the National Eye Institute has shown that a combination of high doses of antioxidants and the mineral zinc can reduce progression of the disorder by about 25%.
If all 6 million Americans with the disease were to take the cocktail of supplements for five years, "about a quarter of a million people who would have developed vision loss won't," said Dr. Emily Chew of the eye institute, one of the leaders of the study.
"This is not a cure," said Dr. Gerald Chader, chief scientific officer of the Foundation Fighting Blindness. "But it has great significance because there are so many people affected and the consequences are so severe."
The treatment is "very safe, very effective [and] . . . pretty cheap," Chader said.
"This is extremely important because there was no proven therapy to prevent the progression of macular degeneration," added Dr. Thomas Friberg of the Eye and Ear Institute at the University of Pittsburgh. "Historically, when you detected macular degeneration, there was nothing you could do to prevent progression."
Although generally safe, the new treatment has side effects that could harm some patients, causing experts to caution that those with the disease should not begin taking the high doses of supplements without consulting their physicians first. One of the ingredients, for example, is beta carotene, which can increase the risk of cancer in smokers. Macular degeneration tends to affect smokers at a higher rate than nonsmokers. The supplement combination might also cause a problem in certain patients with kidney problems.
No one knows what causes age-related macular degeneration, or AMD, but genetics play a major role. Environmental factors are also important. People with high cholesterol levels are at higher risk. Women are at greater risk than men. Eating green leafy vegetables, however, can reduce the risk.
A common feature of AMD is the presence of yellow deposits called drusen in the retina of the eye. Millions of elderly Americans have these deposits without vision loss and don't even know they have the disease.
But as the number of drusen and their size increase, vision begins to be affected. This is usually a long, slow process, and is called "dry" AMD.
For reasons that researchers do not understand, the process of deterioration can suddenly enter a new phase, called "wet" AMD, in which new blood vessels grow into the retina, producing bleeding and vision loss.
"They can go from a slow degenerative process to blindness in three months to six months," Chader said. "This is what we want to stop."
The study enrolled 3,640 patients, ages 55 to 80 years, with intermediate or advanced AMD, at 11 centers around the country. One group received a daily supplement containing 500 milligrams of vitamin C, 400 international units of vitamin E, 15 milligrams of beta carotene, 80 milligrams of zinc oxide and 2 milligrams of copper oxide. (Copper was added to the zinc to prevent the copper deficiency that can occur when people take high doses of zinc.)
A second group received only the antioxidants. A third received only the zinc, and a fourth received a placebo.
The researchers report in the October Archives of Ophthalmology that, after an average of 6.3 years of treatment, progression of the disease was delayed in about 25% of patients among those receiving the full mix of supplements.
"That's a really significant treatment effect, a very important finding," Chew said.
The benefit was lower in patients receiving antioxidants alone or zinc alone.
There were some side effects observed. About 7.5% of the patients taking the supplement combination were hospitalized for genital or urinary side effects, such as prostate problems and kidney stones. But 5% of the placebo group developed the same problems.
In a separate study reported in the same journal, the team found that the supplement combination had no effect on the development of cataracts. "That's probably not too big a surprise," Chader noted, "because cataracts progress much more slowly. The study may just not have lasted long enough to observe an effect."
Consumers can prepare the supplement cocktail by combining the individual ingredients, but Bausch & Lomb--which provided the supplements for the study--will today begin marketing a product called Ocuvite PreserVision that contains the exact combination used in the study.
Additional information about the study is available at http://www.nei.nih.gov/amd