October 29, 2001
Study offers new hope in fighting vision loss in seniors
By Joy Bell
Certain dietary supplements could slow the advancement of a degenerative eye condition and give senior citizens a valuable weapon in the fight against vision loss, according to a study released Oct. 12 by the Emory Eye Center.
Titled the Age-Related Eye Disease Study (AREDS), the 10-year project had two goals:
To assess the clinical course, prognosis and risk factors of age-related macular degeneration (AMD) and cataract.
To evaluate, in randomized clinical trials, the effects of pharmacologic doses of antioxidants and zinc on the progression of AMD and antioxidants on the development and progression of lens opacities (cataract).
This is a particularly important finding since prior to this study, there was no way to slow the progression of AMD, said principal investigator Daniel Martin, a vitreoretinal specialist at the Eye Center.
AREDS was sponsored by the National Eye Institute (NEI) of the National Institutes of Health. The studys findings are reported in the October issue of Archives of Ophthalmology.
AMD is the leading cause of visual impairment and blindness in Americans over 65. It affects the sharp, central vision required for straight-ahead activities such as reading, driving and recognizing faces. The AREDS results show that a dietary supplement of high levels of antioxidants and zinc significantly reduced the risk of advanced AMD and its associated vision loss in patients at high risk of developing advanced stages of AMD.
These same supplements had no significant effect on the development or progression of cataract, the study found. Although the current study indicated that the dietary supplements did not affect the development of cataract, an effect over a longer period of timeor with different doses of these antioxidantscannot be ruled out.
The three stages of AMD analyzed in the study included:
Early AMD: Patients with early AMD have, in one or both eyes, either several small drusen (yellow deposits under the retina) or a few medium-sized drusen; these patients do not have vision loss from AMD.
Intermediate AMD: Patients with intermediate AMD have, in one or both eyes, either many medium-sized drusen or one or more large drusen; in these people, there is usually little or no vision loss.
Advanced AMD: In addition to drusen, patients with advanced AMD have, in one or both eyes, either a breakdown of light-sensitive cells and supporting tissue in the central retinal area (advanced dry form), or abnormal and fragile blood vessels under the retina that can leak fluid or bleed (wet form).
These two forms (wet or dry) of advanced AMD can cause serious vision loss. Scientists are unsure why an increase in the size and number of drusen can lead to advanced AMD, but patients who have advanced AMD in one eye are at especially high risk for developing it in the other eye.
The AREDS scientists found that their patients at high risk of developing advanced stages of AMD lowered this risk by approximately 25 percent when treated with a high-dose combination of vitamins C and E, beta-carotene and zinc.
In the same high-risk groupwhich includes people with intermediate AMD, or advanced AMD in one eye but not the otherthe supplements reduced the risk of vision loss caused by advanced AMD by about 19 percent. For those participants who had either no AMD or early AMD, the supplements did not provide an apparent benefit.
For people at high risk for developing advanced AMD, these supplements are the first effective treatment to slow progression of the disease. Current treatment for advanced AMD is limited, but these dietary supplements will delay the progression to advanced AMD in people at high risk (those with intermediate AMD in one or both eyes, or those with advanced AMD in one eye already).
The supplements are not a cure for AMD, nor will they restore vision already lost from the disease. They will, however, help those at high risk from developing an advanced stage of the disease and help them keep their vision, the study concluded.
At Emory we are also looking at other compounds that may have a promising effect in delaying the onset of macular degeneration, said Paul Sternberg, director of the Vitreoretinal Surgery and Diseases section at the Eye Center. AREDS is the first important step in developing a therapeutic approach to dry macular degeneration. In our labs we are studying several promising agents that may be even more effective.
These findings are only a part of what we will learn from AREDS about macular degeneration, Martin said. We will continue to answer many more questions in the next five years as we continue to follow these patients.