Preventing macular degeneration
By TOM VALEO
Mom was right: Eating carrots and spinach really is good for the eyes.
But carrots and spinach are not enough to stave off one of the most feared diseases of aging -- vision loss caused by macular degeneration.
Age-related macular degeneration (AMD) is the leading cause of vision loss among people older than 50. To guard against AMD, many eye doctors now suggest a vitamin supplement.
That is a switch, because doctors usually argue that a well-balanced diet provides all the nutrition we need. The doctors have a point, because scientific research provides virtually no support for the belief that vitamins prevent disease. That is, until now.
A study conducted by the National Eye Institute has shown that one combination of nutrients protects the eyes against AMD.
"I didn't think this would work," says Reed Paven, a University of South Florida eye doctor. "I generally don't think vitamin pills make much difference." But now he recommends a supplement like the one tested in the National Institutes of Health's Age-Related Eye Disease Study or AREDS. Patients in the study reduced their risk of vision loss by about 25 percent when they took a daily supplement containing vitamins C and E, beta carotene, zinc and copper.
They did not reverse the damage already done, but they slowed the progression of the disease and preserved their remaining vision -- something no other treatment can do. "The AREDS formula is the first demonstrated treatment for people at high risk for developing advanced AMD," says Dr. Frederick Ferris, director of the NEI research.
"Slowing the progression of AMD will save the vision of many who would otherwise have had serious vision impairment."
Even more encouraging, the supplement used in the 10-year study did not contain lutein (LOO-teen), a substance that seems to deter macular degeneration more effectively.
Although abundant in leafy green vegetables, lutein could not easily be extracted and purified until recently. Now it is widely available in vitamin pills that contain the nutrients administered in the AREDS study.
If you're reading this, you probably are not among the 10-million Americans with AMD. The disease involves the breakdown of the light receptors in the macula -- the area in the center of the retina at the back of your eye that enables you to see fine detail, such as these letters.
There are two types of AMD: wet and dry. About 10 percent of people who have it suffer rapid vision loss from wet AMD, which develops when tiny blood vessels start to grow behind the retina. These fragile new vessels tend to leak. The bleeding at the back of the eye damages the retina. The majority of cases involve dry AMD, which is a gradual deterioration that produces blurred vision and blind spots. "It's like getting gray hair," says Dr. Mark Sibley, an ophthalmologist and laser surgeon in St. Petersburg who considers AMD one of the most frustrating vision problems he treats. "It's painless, and it happens very gradually." The only definitive test for AMD is an eye exam. An ophthalmologist can spot either form of AMD just by dilating your eyes and looking at your retinas.
Sibley has taken antioxidants and vitamins to protect his eyes ever since he was in medical school and learned how vulnerable the retina is to oxidation, the chemical reaction that causes metal to rust. Since the mid 1980s, he has given vitamins to his patients at no charge.
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Preventing dry AMD is important, Sibley says, because there is no effective treatment. This type of AMD develops when waste products (from the photo receptors at the back of the eye) start to accumulate behind the retina, forming thin yellow clumps known as drusen. Once drusen develop, nothing can get rid of them.
How can we prevent drusen from forming? Sibley suggests: 1. Exercise and don't smoke. By not smoking, you maintain maximum possible blood flow to the back of the eye. Robust circulation helps remove waste products shed by the photo receptors.
2. Minimize the amount of sunlight that strikes the retina. Keep your eyes shaded and wear sunglasses with UV protection on the lenses. "And I don't mean just sunglasses," Sibley says. "All lenses, even clear lenses, should have an ultraviolet coating." 3. Pay attention to your nutrition. Consume plenty of antioxidants such as vitamins C and E to neutralize the free radicals produced in the eyes, and consider taking a lutein supplement. "Antioxidants and lutein are like sunscreen for your eyes," Sibley says.
In young people, the eye produces its own lutein, but as we age that process slows down, so diet become more important. Otherwise the eye loses its ability to filter damaging blue wavelengths from light hitting the retina.
About 17 years ago, Richard Bone, a professor of biophysics at Florida International University, discovered that macular pigment contains high levels of two carotenoids: lutein and zeaxanthin (ZEE-uh-ZAN-thin). Bone suspected that a diet rich in these two nutrients would prevent the macula from thinning and might even increase its density, bolstering its ability to protect the retina from sunlight. To test his hypothesis, Bone and his longtime collaborator, chemistry professor John Landrum, took a lutein supplement every day for 140 days. Then they measured the density of their macular pigment. The results showed their pigment density increased 20 to 40 percent, which reduced the amount of blue light reaching the retina by 30 to 40 percent. "It's clear that eating foods rich in lutein and zeaxanthin can help increase the concentration of these carotenoids in the eye," Bone said. "We have to avoid saying it's a causal relationship -- we have to wait for the clinical trials before we can make that claim. But my own feeling is that lutein will be found to be very beneficial to the eye."
-- Tom Valeo is a freelance writer specializing in medical and health issues. Write to Tom Valeo, c/o Seniority, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731 or email at email@example.com.
The three most common supplements for staving off macular degeneration are: Ocuvite PreserVision, from Bausch & Lomb; ICaps, from Alcon Laboratories; and VisiVite.
All three duplicate the formula used in the AREDS study -- 500 mg of vitamin C, 400 IU of vitamin E, 15 mg of vitamin A (beta carotene), 80 mg zinc and 2 mg copper.
On the Web
For more information on macular degeneration visit these Web sites:
Macular Degeneration Foundation: www.eyesight.org/
The National Eye Institute: www.nei.nih.gov/amd/
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