Macular Degeneration

Protecting Vision into the Later Years

If you think of your eye as a camera, then the retina is the film. It’s a sheet of light-sensitive cells lining the back of the eyeball. The retina captures images focused on it by the lens, converts the images to nerve impulses and sends the impulses straight to your brain, which then has the task of figuring out whether you’ve set your gaze on a sock, a parking ticket or a double-dip ice cream cone.

Smack in the middle of the retina is an area called the macula. Dense with cells that provide the brain with finely detailed, color-saturated images, the macula is the biological equivalent of Kodachrome. It doesn’t get any sharper or more brilliant than this.

The macula gets the most focused light of any part of the eye. But as vital as light is to vision, it has a mean side. Focused year after year on the retina, light interacts with oxygen and may damage the retina’s cells, causing the accumulation of waste material and sometimes the abnormal growth of tiny blood vessels under the retina. These blood vessels sometimes leak, swell and cause scars that can permanently blur your sight. This whole vision-damaging process is called macular degeneration. After cataracts, it’s the leading cause of blindness in people ages 50 and older.

Fighting for Vision

Symptoms usually develop slowly. “People find it difficult or impossible to see clearly at long distances, to do close work, to see faces or objects clearly or to distinguish different colors,” says Ronald Klein, M.D., professor of ophthalmology at the University of Wisconsin Medical School in Madison. You might mistake that double-dip cone of Bing cherry vanilla for rocky road, for instance.

Treatment for macular degeneration sometimes includes sealing off leaking blood vessels with a laser, a process that at least temporarily stops the spread of damage but that also destroys some retinal cells, Dr. Klein says. So preventing macular degeneration is definitely the way to go.

There’s some evidence that retinal damage involves oxidative chemical reactions, the same reactions that make iron rust and oil turn rancid. In fact, macular degeneration is sometimes called rusting of the retina.

Oxidative reactions occur when oxygen interacts with other substances, setting off a game of molecular musical chairs as unstable molecules lose electrons and then grab electrons from other molecules to balance themselves. Oxidative reactions damage cell membranes and genetic material.

There’s also some evidence that certain dietary components known as antioxidants can help prevent macular degeneration. Vitamins C and E and beta-carotene, a vitamin A precursor, seem most helpful. These nutrients can inhibit oxidative reactions. Some minerals, such as zinc, copper and selenium, may also be involved. These minerals are needed in small amounts for the body to make antioxidant enzymes that help protect the eye.

Multivitamins Get Some Votes

Several over-the-counter multivitamin/mineral products, including Icaps and Ocuvite (available in health food stores), are marketed to people with either macular degeneration or cataracts. And at least two small studies suggest that In one study, one-third of the people with macular degeneration scored better on vision tests after taking supplements for six months, while only 10 percent of the people not taking supplements scored better. In addition, about 40 percent of the people in the nonsupplement group continued to have deteriorating eyesight compared with only 22 percent of the people in the supplement group.

“There’s certainly good reason to look further at possible nutritional protection for macular degeneration,” Dr. Klein says. He and some other researchers, however, feel the case is far from solid, at least right now. They’re waiting for the results of the Age-Related Eye Disease Study, a ten-year nationwide study now in progress that is looking to see whether a mix of vitamins and minerals, including vitamin C, vitamin E, beta-carotene and zinc, can cut people’s risk of developing macular degeneration.

“If my patients ask about nutrients for macular degeneration, I tell them the facts: that there’s some suggestion of benefit but nothing conclusive,” Dr. Klein says. “I don’t encourage them one way or the other.”

Other ophthalmologists do recommend nutrients. “I’m not saying the evidence is in, either. But the facts so far seem promising enough for me to tell my patients that certain nutrients may help,” says Randall Olson, M.D., professor and chairman of the Department of Ophthalmology at the University of Utah School of Medicine and director of the John A. Moran Eye Center, both in Salt Lake City.

Here’s what research shows may help slow down macular degeneration.

Beta-Carotene Gets an A for Eyes

There’s no doubt that vitamin A plays an important role in vision. In the retina, a form of vitamin A helps convert light to nerve impulses. Two signs of vitamin A deficiency are night blindness and trouble recovering vision after being temporarily blinded by bright light, such as the headlights of an oncoming car.

When it comes to macular degeneration, however, it seems to be beta-carotene and perhaps other related compounds that provide the protection. These nutrients act as antioxidants, stopping chain reactions of free radicals, those unstable molecules that cause so much damage, by offering their own electrons.

So far, evidence is limited to several dietary studies that suggest that people who eat plenty of beta-carotene-rich fruits and vegetables are less likely than normal to develop macular degeneration. A study at Harvard Medical School, for instance, found that people who got at least 8,700 international units of beta-carotene a day had 50 percent less risk of developing macular degeneration than those getting less than that amount.

In another study, people who ate beta-carotene-packed carrots, broccoli, spinach and apricots on a daily basis had only about half of the risk of macular degeneration of people who ate hardly any of those foods.

Doctors who recommend over-the-counter beta-carotene supplements to prevent macular degeneration or slow its progression prescribe 25,000 international units daily, Dr. Olson says.

Even though beta-carotene supplements are being used in ongoing studies, these supplements have not yet been proven to help prevent macular degeneration. That fact, along with the possibility that other nutrients in fruits and vegetables besides beta-carotene may be offering protection, leads many researchers to recommend food sources of beta-carotene rather than supplements. You’ll be well into the high-intake range found protective in studies if you get five servings of orange, yellow or dark green, leafy vegetables every day.

Orange Aid for Eyes

Need another good reason to stock up in the produce section the next time you’re shopping for groceries? It turns out that vitamin C, an antioxidant that’s highly concentrated in the eye, may help shield retinal cells from oxygen-generated damage.

Studies suggest that people who get plenty of vitamin C in their diets are less likely to develop macular degeneration than those whose vitamin C intakes are low. Harvard University researchers, for instance, found that about 80 milligrams of vitamin C a day reduced the risk of macular degeneration by about 30 percent.

Doctors who recommend vitamin C to prevent or slow the progress of macular degeneration suggest 500 milligrams or more daily. That’s many times the Daily Value of 60 milligrams. One researcher, Ben C. Lane, O.D., director of the Nutritional Optometry Institute in Lake Hiawatha, New Jersey, believes that there is good reason to limit your vitamin C intake to less than 3,000 milligrams daily. He has found that this much vitamin C is associated with retinal macular puckering and increased risk of retinal detachment, which involves the retina pulling away from the back of the eyeball. (If you are very nearsighted, Dr. Lane adds, you should take no more than 1,000 milligrams daily. Nearsighted people are at higher than normal risk for retinal detachment.)

Prescriptions for Healing Some doctors recommend these nutrients to help prevent or slow the progress of macular degeneration. Nutrient Daily Amount Beta-carotene 25,000 international units Copper 1.5-9 milligrams (1 milligram for every 10 milligrams of zinc) Selenium 50-200 micrograms Vitamin C 500 milligrams Vitamin E 400-800 international units Zinc 15-90 milligrams Plus a multivitamin/mineral supplement containing the Daily Values of all essential vitamins and minerals MEDICAL ALERT: If you have macular degeneration, check with your doctor before taking supplements. Selenium supplements in excess of 100 micrograms daily should be taken only under medical supervision. It's a good idea to check with your doctor before beginning vitamin E supplementation that exceeds 600 international units daily. People who are taking anticoagulants should not take vitamin E supplements. Don't take more than 15 milligrams of zinc daily without medical supervision.

Vitamin E Eye Guard

Along with vitamin C and beta-carotene, vitamin E is a well-known antioxidant. Incorporated into the fatty membranes that enclose cells, vitamin E shields cells from free radical damage. In the retina, vitamin E may help dampen the reactions between light and oxygen that may eventually cause retinal cells to malfunction.

A few studies suggest that vitamin E can be helpful in preventing macular degeneration. Researchers at Johns Hopkins University School of Medicine in Baltimore, for instance, found that people with high blood levels of vitamin E had only half of the risk of developing macular degeneration compared with people with low blood levels.

“I feel that we don’t yet know enough about how nutrients such as vitamin E work in the retina to make recommendations regarding supplement use,” says Sheila West, Ph.D., associate professor of ophthalmology at Johns Hopkins University School of Medicine and the study’s main author.

Doctors who do recommend vitamin E generally stay in the range of 400 to 800 international units, Dr. Olson says. Even diets that include lots of vitamin E–rich foods such as wheat germ and almonds can’t provide these high amounts, so supplementation may be in order. The Daily Value for vitamin E is 30 international units. (It’s a good idea to talk to your doctor if you’re considering taking more than 600 international units of vitamin E daily.)

Zinc May Slow Down Damage

It’s well-known that the retina contains high concentrations of zinc, an essential mineral. “Zinc appears to play an important role in the metabolism of the retina,” Dr. Lane says. Zinc-deficient animals show signs of retinal breakdown, and people who are shortchanged when it comes to zinc seem to be at higher than normal risk for macular degeneration. But the zinc needs to be in balance with other minerals and not excessive, says Dr. Lane.

One study, from the Louisiana State University Eye Center in New Orleans, seems to show that zinc can help keep sight sharp as we age. That study included 151 older, healthy people with early signs of macular degeneration. Half took daily doses of 100 to 200 milligrams of zinc sulfate for 18 to 24 months. The other half took placebos (harmless blank pills).

The eyes and vision of the people in both groups were checked before and after the study. Those taking supplemental zinc were found to have significantly less loss of vision compared with those taking the placebos.

Doctors who recommend zinc to prevent or slow macular degeneration suggest amounts ranging from the Daily Value of 15 milligrams up to 80 or 90 milligrams a day. Dr. Olson recommends 50 milligrams, while Dr. Lane bases his initial dosage on each person’s zinc status. “It may be necessary to start a person at a fairly high amount, then cut back as his status returns to normal,” he says. Over-the-counter supplements such as zinc amino acid chelate, zinc gluconate and zinc aspartate are good sources of zinc, Dr. Lane adds.

One thing is for sure with zinc: More is not necessarily better, and doses that exceed the Daily Value deserve medical supervision. Why? For one thing, zinc competes with copper in the body, which means that too much zinc can make you deficient in copper. “That’s bad, because copper also apparently plays a role in macular degeneration,” Dr. Lane says. (Copper, along with zinc, is needed for the body to produce a potent antioxidant enzyme called superoxide dismutase.)

You should be getting one milligram of copper for every ten milligrams of zinc. And as with zinc, don’t overdo copper. It is possible to accumulate too much copper, even when it’s taken in fairly small amounts. This can be bad for your health.

Selenium Adds Antioxidant Power

Doctors sometimes fill out their antioxidant prescriptions with selenium, a mineral that is involved in the body’s production of glutathione peroxidase, yet another protective enzyme found in the eye and in other parts of the body.

“In theory, selenium should be helpful in preventing macular degeneration, but in reality, there is no good proof yet that it is,” Dr. Lane explains. He recommends supplements only to people found to be deficient. Dr. Olson does not recommend individual selenium supplements, but he does recommend multi vitamin/mineral products such as Icaps and Ocuvite, which contain selenium.

Doctors who recommend supplements suggest 50 to 200 micrograms a day. Doses of more than 100 micrograms daily should be taken only under medical supervision; even in small amounts, selenium can be toxic. For foods rich in selenium, try garlic, onions, mushrooms, cabbage, grains and fish.