"Wet" macular degeneration progressively robs patients of their central vision. The Merck Manuals says 90 percent of all cases of blindness due to macular degeneration occur in the 10 percent of patients who have the wet form, which always occurs in patients who have the more slowly progressing "dry" form first.
Physiology
As eyes age, they become less efficient in clearing away waste proteins generated by the macula, the center of the retina, which allows for sharp vision in the middle of the visual field. Accumulated waste proteins, plus fatty-looking deposits in the macula called drusen, are the hallmarks of dry macular degeneration. In wet macular degeneration, the macula incurs additional damage when abnormal new blood vessels grow underneath it. When the blood vessels leak, fluid pressure displaces the macula. Unlike dry macular degeneration, the wet form rapidly destroys vision.
Goal
Wet macular degeneration can be treated, but in general, the treatments cannot reverse any loss of vision that has already occurred. Instead, the goal of treatment is to prevent further damage and further loss of vision, so early diagnosis and treatment are critical.
Injections
The National Eye Institute, or NEI, says treatment of wet macular degeneration involves injections of anti-VEGF into the eye. This compound inhibits a growth factor that allows new blood vessels to form. The procedure is done on an out-patient basis. First, the doctor numbs the eye, then injects the anti-VEGF to slow the course of the disease. Unlike other treatments, in some cases, this anti-VEGF injection can slightly improve vision. The Merck Manual also lists ranibizumab, bevacizumab and pegaptanib as drugs that can be injected into the eye to inhibit blood vessel growth.
Surgery
In this outpatient procedure, the doctor uses a laser to destroy abnormal new blood vessels under the macula. The procedure is risky because the laser can also damage healthy eye tissue, and the NEI says that only a low percentage of patients can take advantage of it.
Photodynamic Therapy
In this outpatient procedure, the doctor injects a photodynamic compound into an intravenous line in the patient's arm. Circulation carries the compound to the eye, where it sticks to the new blood vessels. The doctor shines a light on the macula to activate the compound, causing it to destroy the blood vessels. The destruction is limited to the blood vessels, making this a more precise treatment than laser surgery, according to the NEI.
Prognosis
Despite any of these treatments, the loss of vision can continue. At best, the treatments will slow or halt the damage. Often, the treatments need to be repeated. Anti-VEGF injections, for example, usually must be given monthly, according to the NEI, and both laser surgery or photodynamic treatment may need to be repeated.
