Age-related macular degeneration is a degenerative disease of the macula, the central part of the retina. It results in loss of central vision, which is necessary for most daily activities, and can cause legal blindness. This disease is the most common cause of poor vision among elderly persons
There are two forms of macular degeneration: The "dry" form is marked by changes in the macula without bleeding or leakage of fluid. The "wet" form includes leakage and/or bleeding from new blood vessel growth beneath the retina.
Macular degeneration is thought to be due to destruction of the fatty acids in the rods and cones of the eyes. Thus, antioxidant nutrients have long been thought to be protective (see Nutritional Considerations).
The disease is characterized by gradual vision loss. However, "wet" macular degeneration can result in blindness within weeks. Other symptoms include distortion of straight lines, slow recovery of vision after leaving sunlight and going indoors, and changes in color vision.
- Age: Macular degeneration rarely occurs in persons under age 55. The prevalence is nearly 1 percent in those aged 70 and older, and increases to more than 15 percent in those over 90.
- Smoking: Individuals who smoke have more than double the risk, compared with those who have never smoked. Risk may remain elevated for 15 or more years after smoking cessation.
Additional probable risk factors include nutritional deficiencies (see Nutritional Considerations) and family history of the disease. Some studies suggest that hypertension, sunlight exposure, and cataract surgery also increase the risk of macular degeneration. However, further study is necessary to define these risks.
Age-Related Macular Degeneration (ARMD): Diagnosis and Treatment
- The evaluation begins with a medical history and a physical examination.
- Direct visualization of the macula by use of an ophthalmoscope usually diagnoses the disease.
- In some cases, further ophthalmologic testing may be recommended.
- Smoking cessation is necessary.
- In cases of rapidly progressive "wet" macular degeneration, laser therapy or medical drugs may be useful. However, in most cases, no specific medical or surgical treatment exists.
- Gingko biloba has been marketed as an herbal therapy for macular degeneration. In one small study, it did improve vision in affected individuals. However, further investigation is necessary.
- Steroids injections into the eye are a possible therapy, but require further study.
Age-Related Macular Degeneration (ARMD): Nutritional Considerations
Dietary factors appear to play an important role. In epidemiologic studies, the following factors are associated with reduced risk of onset or progression of the disease:
- Maintenance of ideal weight: Studies have found a higher risk for macular degeneration in patients who are overweight, particularly those with abdominal obesity. In contrast, regular exercise is associated with lower risk.
- Low fat intake: Studies have found associations between high intakes of saturated fat and cholesterol and macular degeneration. Other studies have implicated vegetable fat and total fat intake.
Regular consumption of processed baked goods doubled the risk compared with those who did not regularly consume these foods, possibly by causing increased blood cholesterol or inflammation.
- High consumption of fruits and vegetables: The carotenoids lutein and zeaxanthin are essential molecules in the macula. They are abundant in dark-green, leafy vegetables and appear to play an important role in the prevention of macular degeneration.
Several studies have found that people with high intake of fruits and vegetables had a significantly lower risk compared with those who have low intakes. The Eye Disease Case Control Study found that individuals who had the highest intake of carotenoids had a more than 40 percent lower risk compared with those who consumed the least. Intakes of collard greens and spinach, both rich in lutein, were found to be the most protective. Further, two large studies, the Health Professionals Follow-Up Study and the Nurses' Health Study, found that those who consumed the most fruit (three or more servings per day) had a lower risk.
- Antioxidant supplements: In the Age-Related Eye Disease Study, individuals with moderate or advanced macular degeneration who received 500 milligrams of vitamin C, 400 International Unites of vitamin E, 15 milligrams of beta carotene, and 80 milligrams of zinc had significantly reduced progression of their disease, compared with subjects receiving a placebo. However, caution is advised considering that other studies have shown that beta-carotene supplementation may increase lung cancer risk among smokers, and that high doses of vitamin E may increase cardiovascular risk.
In the Lutein Antioxidant Supplementation Trial, a 10-milligram supplement of lutein taken daily, alone or with a vitamin supplement, improved vision when compared with a placebo. Lutein supplementation also improved vision in other controlled trials.