Zinc, Antioxidants Prevent Some Forms of Vision Loss

From the WebMD Archives

Oct. 12, 2001 -- A mixture of antioxidant vitamins and zinc supplements can prevent further vision loss in people with one of the most common causes of visual impairment and blindness in the U.S. Researchers recommend that people over 55 visit their eye doctor to determine their risk of developing this type of vision loss.

Researchers found that people at risk of losing more sight due to a condition called "age-related macular degeneration" (AMD) could prevent further vision loss by taking a combination of zinc and antioxidants, including vitamins C and E and beta-carotene.

Age-related macular degeneration is a medical problem in which a particular part of the eye called the macula begins to deteriorate. The macula allows us to see things in the center of our field of vision. Someone with this eye disease who looks at a picture would not be able to see the images in the center of the picture but might be able to see things around the edges.

"This is an exciting discovery because for people at high risk for developing advanced AMD, these dietary supplements are the first effective treatment to slow the progression of the disease," says Paul A. Sieving, MD, PhD, in a news release.

Currently, the only available treatment for AMD, which is the No. 1 cause of vision loss and blindness in people 65 years and over, is laser therapy to reduce the chance of further vision loss; but even that only works in people with certain types of the disease.

Since treatment options are limited, doctors are looking for ways to either prevent the disease or slow the progression once it develops.

Investigators from the Age-Related Eye Disease Study Research Group in 11 areas around the country followed over 3,600 people -- some with AMD and some without. They were divided into several groups, including people who took either antioxidants or zinc and those who took both. The results are published in the October issue of the Archives of Ophthalmology.

The antioxidants were taken once a day at a dose of 500 mg of vitamin C, 400 IU of vitamin E, and 15 mg of beta-carotene. Zinc was given as 80 mg of zinc oxide along with 2 mg of copper in the form of cupric oxide to prevent anemia, which can occur from too much zinc.

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Unfortunately, the researchers did not find any benefit for people with no signs of AMD or for those with very mild forms of the disease.

But the researchers were able to identify certain groups of people who already had AMD that were likely to develop continued loss of vision. These are characteristics that can only be seen by your eye doctor during an exam in which your pupils are dilated.

There was good news for this group of people, who have a high risk of developing very poor vision or going blind. Among this group, those taking both antioxidants and zinc were 25% less likely to develop advanced stages of the disease. Those taking just antioxidants or zinc alone also saw some protection, though to a lesser degree.

Side effects were infrequent and minor in this study, although people taking zinc developed urinary tract infections slightly more often than others, and yellowing of the skin related to large doses of beta-carotene was reported slightly more often by people taking antioxidants.

"The supplements are not a cure for AMD, nor will they restore vision already lost from the disease," says Sieving. "But they will play a key role in helping people at high risk for developing advanced AMD keep their vision." He is director of the National Eye Institute, which sponsored the study.

So, can you just eat a healthy diet and get this same protection?

"Previous studies have suggested that people who have diets rich in green, leafy vegetables have a lower risk of developing AMD," says Frederick Ferris, MD, director of clinical research at the National Eye Institute, in a news release.

However, Ferris, who is also chairman of the group responsible for this study, says that the high levels of dietary supplements that were taken in this study are very difficult to achieve from diet alone.

The researchers suggest that anyone 55 years old and over should have their eyes examined by a doctor to look for these hidden signs of AMD. If this current study's findings hold true, antioxidants and zinc could be at least one answer for stopping further vision loss in some people.

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