Macular degeneration (MD) is an eye disorder affecting more than 13 million Americans, and is generally considered to be irreversible. In fact, more people are affected by MD than by glaucoma and cataracts combined. It is the leading cause of blindness in those over the age of 55, with a new case of age-related macular degeneration (AMD) diagnosed every three minutes. (Age-related macular degeneration is a term used for the disorder when it affects people over the age of 60.) The cause of MD is not known, but the condition runs in families, and it likely has a genetic component. It affects an equal number of women and men, but seems to be more common among Caucasians than African-Americans.
Macular degeneration refers to the breakdown of the macula - the central portion of the retina. The function of the retina is to receive visual images, to partially analyze them and transmit the information to the brain. The macula contains the most concentrated collection of light-sensing nerves in the retina and is responsible for producing the most critical aspects of vision. There is a rich supply of blood vessels that carry oxygen and important nutrients to the retina that are required for healthy vision, and disruption of this vasculature can be a contributing factor in MD. The retina has no pain nerve fibers, therefore most diseases that affect the retina do not cause pain.
There are actually two forms of MD. The first, atrophic or dry MD, results from a gradual breakdown and degeneration of critical photoreceptors in the eye that provide night vision and visual acuity. The second, exudative or wet MD, is caused by leaks in the blood vessels of the retina. The bleeding causes scarring and retinal tissue death. About 80 to 85 percent of those with MD have the atrophic form; but most cases of severe vision loss can be attributed to the exudative form. About 10 percent of those with dry MD will also develop the wet form.
Causes and Symptoms
Although there are no definitive answers as to what specifically causes MD, there are a few emerging theories that may help explain what circumstances lead to the problem. Since the macula depends for its healthy functioning on one of the highest rates of blood flow through its blood vessels, anything that interferes with this blood flow can cause the macula to malfunction.
The following dietary or lifestyle choices can reduce the supply of oxygen and vital nutrients to the retina and eventually lead to the death of cells in the retina and macula:
- Smoking can decrease blood supply by causing a narrowing of the blood vessels and a thickening of the blood, much the same as in a heart attack or stroke.
- High saturated-fat diets can cause plaque buildup along blood vessel walls, including the macular vessels, which impedes blood flow.
- A lack of antioxidants, such as vitamin C, vitamin E and lutein may increase the ability of plaque to stick to the blood vessel walls and promote the damage of the tissue.
With macular degeneration there is typically a loss of vision in both eyes. The initial symptom may be a distortion of vision in one eye, causing straight lines to appear wavy. Eventually, loss of central vision worsens, making it difficult to see at long distances, read up close, see faces clearly or distinguish colors. Peripheral vision (what you see out of the corners of your eyes) is not affected.
Recommended Lifestyle Changes
- Don't smoke and avoid exposure to second-hand smoke.
- Protect your eyes. Be sure to wear sunglasses that contain UV protection.
- Follow a diet that is very low in saturated fat and rich in antioxidants, focusing on vegetables, fruit, and legumes including soy, whole grains and fish.
- Eat antioxidant-rich berries, especially blueberries, frequently.
- Increase your intake of antioxidants such as vitamins C and E, lutein and zinc.
Nutrition and Supplements
Try to choose foods or take supplements that contain vitamin C, vitamin E and lutein, as well as zinc. Vitamin C-rich foods include citrus fruits, melons, tomatoes, potatoes and broccoli. You can get vitamin E from soybeans, greens, fish, wheat germ, nuts and seeds. Dietary sources of zinc are legumes (peas, dried beans, garbanzos/chickpeas, black-eyed peas, lentils and soy products) and whole grains. The carotenoid pigment lutein is found naturally in spinach, kale, collard greens, romaine lettuce and peas. Other protective compounds are the red and purple pigments found in berries and other fruit. Eat berries, especially blueberries, often. You can also get these pigments into your diet with supplements of bilberry, grape seed extract or pine bark extract. My recommendations for daily vitamin E are to take 400-800 IU of natural mixed tocopherols, or at least 80 mg of natural mixed tocopherols and tocotrienols. People under 40 should take 400 IUs a day; people over 40, 800 IUs.
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