Vitamins, fatty acids and immune system reactions may all play roles in preventing or at least slowing the progress of macular degeneration, the leading cause of blindness in people over age 55.
Macular degeneration is a disease that affects the macula, the portion of eye that surrounds the central part of the retina. The retina absorbs and processes light; the macula helps focus that light for tasks that require close, concentrated vision, such as reading, doing Sudoku puzzles or working on a computer.
Because it is a progressive disease, macular degeneration develops in stages. In the early stages, vision loss may be barely perceptible. As it advances, nearly all central vision may be lost. However, since the disease doesn’t affect peripheral vision, complete vision loss is rare.
“Dry” vs. “Wet”
There are two forms of macular degeneration: “wet” and “dry.” Both begin with a build-up of small protein deposits under the cells that nourish the retina; these deposits cause no symptoms and patients may not be aware of them until they have their eyes examined.
In the “dry” form, which includes 90 percent of cases, the cells that nourish the retina begin to deteriorate. Vision loss progresses slowly, and vision can remain stable for years.
In the remaining 10 percent of cases—the “wet” form—vision may change suddenly, with marked distortions and wavy lines. Blood and scar tissue appear under the retina, which signals that abnormal blood vessels are growing beneath the retina and causing severe scarring around the cells that nourish it.
Interestingly, a chemotherapy medication commonly used to treat colon cancer, Avastin, is one of the leading treatments for “wet” macular degeneration. Avastin inhibits the growth of these blood vessels and can restore vision. The company that makes Avastin has also released Lucentis, a non-chemotherapy form of Avastin which is FDA-approved for macular degeneration treatment. Patients who have been treated with injections of Lucentis or Avastin have seen dramatic results; some legally blind patients have regained enough vision to read again. Inmost cases, multiple treatments are needed in order to maintain the positive effects.
A clinical trial sponsored by the National Eye Institute, The Comparisons of Age-Related Macular Degeneration Treatments Trials (CATT) is currently comparing the safety and effectiveness of Avastin and Lucentis and studying how frequently the drugs should be given. Because a single Lucentis treatment costs approximately $2,000 per dose, while an Avastin treatment for macular degeneration costs approximately $50-$100, the results of the study could have a significant impact on treatment costs.
Clinical Research Trials
While there is currently no treatment for the “dry” form of macular degeneration, recent clinical research has suggested that certain nutrients may help reduce the progression of both forms.
Nutritional studies continue to emphasize the importance of a balanced diet, high in specific fruits and vegetables that support eye health. Based on the first Age-Related Eye Disease Study (AREDS1), retina specialists recommend that patients with moderate to advanced stages of macular degeneration take a daily supplement containing high concentrations of Vitamins C, E, copper, zinc and beta-carotene (if the patient is a nonsmoker). This supplement reduces the progression of macular degeneration by a significant 30% over five years. In addition, based on the results of a collaborative research effort with scientists at The Scripps Research Institute and The Salk Institute, we also recommend that patients increase their intake of foods high in specific bioflavonoids, which protect from the type of injury that causes macular disease.
The Age-Related Eye Disease Study 2 (AREDS2), currently underway at the National Eye Institute, is a five-year clinical research trial studying whether certain vitamins and fatty acids can help prevent or slow down the progress of macular degeneration. Researchers are studying omega 3 fatty acids, such as those found in salmon, tuna, halibut, walnuts, olive oil and other foods, as well as lutein, which acts as a natural “sunscreen” for the retinas. Lutein is present in tomatoes, squash, carrots and dark green leafy vegetables.
Another clinical research trial is studying complement inhibitors as a means of preventing macular degeneration. Part of our natural immune system, the complement system is a series of chemical reactions that helps (complements) antibodies to regulate bacteria, viruses and infections within our bodies. The pathway that the complement system uses to defend us from disease-producing organisms is called complement activation. While complement activation is an important part of immune response, excessive activation can have negative effects on the body. Researchers have found that excessive complement activation plays a role in the development of macular degeneration, and believe that by inhibiting the complement cascade process, we may be able to protect against macular degeneration. Clinical trials of complement inhibitors are still in the early stages and we do not expect to have medications available for at least five years, but the research appears promising.
Anne M. Hanneken, MD, is an ophthalmologist with Scripps Memorial Hospital La Jolla. Join Dr. Hanneken for a free seminar on macular degeneration on Friday, March 19, at 10 a.m. at the Schaetzel Center on the hospital campus. To register, please call 1-800-SCRIPPS (1-800-727-4777).