New Haven, Conn. * A new light sensitive drug used to treat the most severe form of macular degeneration, which is the leading cause of blindness in people over 50, is being tested at Yale School of Medicine.
The drug, verteporfin, is expected to receive approval by the U.S. Food and Drug Administration in the next few weeks under the name Visudyne. The Yale Department of Ophthalmology and Visual Science has been in clinical trial with the drug for four months.
"The drug, verteporfin, is a photosensitizing agent that is injected into the patient's arm," said Daniel Berinstein, M.D., assistant professor of ophthalmology. "The medication is then activated by light from a laser for about 90 seconds. The laser is weak enough so that it does not damage the retina, but strong enough to activate the medication and selectively treat the abnormal blood vessels associated with the degeneration."
Once activated, the verteporfin works by closing the abnormal blood vessels and, it is hoped, improving or stabilizing the patient's vision.
Berinstein said the clinic administered the treatment to about 12 patients and a three-month follow up is in progress to determine the effectiveness of the procedure. The drug's developers, CIBA Vision and QLT PhotoTherapeutics, found in their own study that the treatment led to improvement for some, but not all, patients. The company said the drug was not useful for patients with longstanding vision loss or whose eye or eyes have been significantly damaged by age-related macular degeneration (AMD).
AMD affects the central field of vision essential for activities such as reading and driving. Peripheral, or side vision, is retained.
There are two types of AMD. The "dry" form is found in 85 percent of patients with AMD and is characterized by deposits of yellow material in the retina.
The new treatment is designed for the more severe, but less common, "wet" AMD, which, although it affects only 15 percent of patients with AMD, accounts for 90 percent of severe vision loss associated with the condition.
The wet form of AMD is caused by the growth of abnormal blood vessels across the macula, or the central part of the retina. These abnormal vessels leak fluid and blood into the tissue at the back of the eye, causing a blister to form in the retina. This leads to scar tissue and a large blind spot.
AMD tends to occur in one eye at a time, but 50 percent of patients with wet AMD in one eye will develop the condition in their second eye within five years. The progression of the disease varies from a few months to three years. Untreated, the majority of eyes affected with wet AMD will become functionally blind within three years.
One of the first noticeable symptoms of wet AMD is a distortion of straight lines.
Berinstein said the only other approved treatment currently available for 10 to 20 percent of cases of wet AMD is laser photocoagulation, where laser light is used to destroy the abnormal leaky blood vessels. But because this treatment is non-selective, the overlying and surrounding retina is also destroyed, causing permanent central vision loss.