While vision loss cannot be reversed, early detection is important because treatments are available that may halt or slow the progression of the wet form of ARMD. Some treatments for the dry form were still in early clinical trials in 2001.
In wet-type ARMD and in senile disciform macular degeneration, new capillaries grow in the macular region and leak. This leaking of blood and fluid causes a portion of the retina to detach. Blood vessel growth, called neovascularization, can be treated with laser photocoagulation in some cases, depending upon the location and extent of the growth. Argon or krypton lasers can destroy the new tissue and flatten the retina. This treatment is effective in about half the cases but results may be temporary. A concern exists that laser therapy causes the laser to destroy the photoreceptors in the treated area. If the blood vessels have grown into the fovea (a region of the macula responsible for fine vision), treatment may be impossible. Because capillaries can grow quickly, this form of macular degeneration should be handled as an emergency and treated immediately.
Photodynamic therapy (PDT) is a promising new treatment approved by the Food and Drug Administration in 2000. With PDT, the patient is given a light-activated drug intravenously with no damage to the retina. The drug, Visudyne, is absorbed by the damaged blood vessels. The affected area on the retina is exposed to a nonthermal laser light that activates the drug exactly 15 minutes after the infusion begins. It must be exactly 15 minutes for the treatment to be successful. The light chemically alters the drug, and any leakage from choroidal neovascularization (CNV) ceases. Patients require retreatment every three months during the first year of therapy, and should be advised to avoid bright light or sun exposure for several days after therapy.
Another form of treatment for the wet form of ARMD is radiation therapy with either x rays, or a proton beam. Growing blood vessels are sensitive to treatment with low doses of ionizing radiation. The growth of nerve cells in the retina is stunted. They are insensitive and thus are not harmed by this treatment. External beam radiation treatment has shown promising results at slowing progression in limited, early trials.
Other therapies that are under study include treatment with alpha-interferon, thalidomide, and other drugs that slow the growth of blood vessels. Subretinal surgery also has shown promise in rapid-onset cases of wet ARMD. This surgery carries the risk of retinal detachment, hemorrhage, and acceleration of cataract formation. A controversial treatment called rheotherapy involves pumping the patient’s blood through a device that removes some proteins and fats. As of 2001, this had not been proven to be safe or effective.
Consumption of a diet rich in antioxidants (beta carotene and the mixed carotenoids that are precursors of vitamin A, vitamins C and E, selenium, and zinc), or antioxidant nutritional supplements, may help prevent macular degeneration, particularly if started early in life. Research has shown that nutritional therapy can prevent ARMD or slow its progression once established.
Researchers also are working on therapies to treat the dry form of macular degeneration. Low-energy laser treatment for drusen is currently in clinical trials as of 2001. In this treatment the ophthalmologist uses a diode laser to reduce the drusen level. Some ophthalmologists were already performing this procedure “off-label,” without FDA approval.
Another treatment, approved overseas but not in the United States, treats dry ARMD by implanting a miniaturized telescope to magnify objects in the central field of vision. This does not treat the disease, but aids the patient’s vision in only the very severe cases of ARMD.
The dry form of ARMD is self-limiting and eventually stabilizes, with permanent vision loss. The vision of patients with the wet form of ARMD often stabilizes or improves even without treatment, at least temporarily. However, after a few years, patients with this type are usually left without acute central vision.
Many macular degeneration patients lose their central vision permanently and may become legally blind. However, macular degeneration rarely causes total vision loss. Peripheral vision is retained. Patients can compensate for central vision loss, even when macular degeneration renders them legally blind. Improved lighting and low-vision aids can help even if visual acuity is poor. Vision aids include special magnifiersallowing patients to read, and provide telescopic aids for long-distance vision. The use of these visual aids plus the retained peripheral vision assist in maintaining patient independence.
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