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 (ARA)
- Findings from a nationwide clinical trial reported that high
levels of antioxidants and zinc significantly reduce the risk
of advanced age-related macular degeneration (AMD) and its associated
vision loss.
Scientists found that people
at high risk of developing advanced stages of AMD, a leading
cause of vision loss, lowered their risk by about 25 percent
when treated with a high-dose combination of vitamin C, vitamin
E, beta-carotene and zinc. In the same high risk group -- which
includes people with intermediate AMD, or advanced AMD in one
eye but not the other eye -- the nutrients reduced the risk of
vision loss caused by advanced AMD by about 19 percent. For those
study participants who had either no AMD or early AMD, the nutrients
did not provide an apparent benefit. The clinical trial -- called
the Age-Related Eye Disease Study (AREDS) -- was sponsored by
the National Eye Institute (NEI), one of the Federal government's
National Institutes of Health.
- "This is an exciting discovery
because, for people at high risk for developing advanced AMD,
these nutrients are the first effective treatment to slow the
progression of the disease," said Paul A. Sieving, M.D.,
Ph.D., director of the NEI. "AMD is a leading cause of visual
impairment and blindness in Americans 65 years of age and older.
Currently, treatment for advanced AMD is quite limited. These
nutrients will delay the progression to advanced AMD in people
who are at high risk -- those with intermediate AMD in one or
both eyes, or those with advanced AMD in one eye already.
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"The nutrients are not a
cure for AMD, nor will they restore vision already lost from
the disease," Dr. Sieving said. "But they will play
a key role in helping people at high risk for developing advanced
AMD keep their vision."
A common feature of AMD is the
presence of drusen, yellow deposits under the retina. Often found
in people over age 60, drusen can be seen by an eye care professional
during an eye exam in which the pupils are dilated. Drusen by
themselves do not usually cause vision loss, but an increase
in their size or number increases a person's risk of developing
advanced AMD, which can cause serious vision loss. |
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Advanced AMD can cause serious
vision loss. Scientists are unsure about how or why an increase
in the size or number of drusen can sometimes lead to advanced
AMD, which affects the sharp, central vision required for the
"straight ahead" activities, such as reading, driving
and recognizing faces of friends.
"Previous studies have suggested
that people who have diets rich in green, leafy vegetables have
a lower risk of developing AMD," said Frederick Ferris,
M.D., director of clinical research at the NEI and chairman of
the AREDS. "However, the high levels of nutrients that were
evaluated in the AREDS are very difficult to achieve from diet
alone.
"Almost two-thirds of AREDS
participants chose to take a daily multivitamin in addition to
their assigned study treatment," Dr. Ferris said. "The
study also showed that, even with a daily multivitamin, people
at high risk for developing advanced AMD can lower the risk of
vision loss by adding a formulation with the same high levels
of antioxidants and zinc used in the study."
Dr. Ferris said some people with
intermediate AMD may not wish to take large doses of antioxidant
vitamins or zinc medical reasons. "For example, beta-carotene
has been shown to increase the risk of lung cancer among smokers,"
he said. "These people may want to discuss with their primary
care doctor the best combination of nutrients for them. With
the use of the high levels of zinc, it is important to add appropriate
amounts of copper to the diet to prevent copper deficiency."
The AREDS participants reported
few side effects from the treatments. About 7.5 percent of participants
assigned to the zinc treatments -- compared with five percent
who did not have zinc in their assigned treatment -- had urinary
tract problems that required hospitalization. Participants in
the two groups that took zinc also reported anemia at a slightly
higher rate; however, testing of all patients for this disorder
showed no difference among treatment groups. Yellowing of the
skin, a well-known side effect of large doses of beta-carotene,
was reported slightly more often by participants taking antioxidants.
"The AREDS formula is the
first demonstrated treatment for people at high risk for developing
advanced AMD," Feris said. "Slowing the progression
of AMD to its advanced stage will save the vision of many who
would otherwise have had serious vision impairment." |
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