Photodynamic Therapy Shows Promise In Halting Progression Of Age-Related Macular Degeneration

Emory Eye Center can now offer new hope to patients with the wet form of age-related macular degeneration (AMD), the leading cause of blindness in Americans over age 50.

PDT is significant because there is no cure for wet AMD and the most widely available treatment -- photocoagulation therapy with a heating laser -- can cause blind spots and can be used for about 10 percent of patients with the disease. About 40 to 60% of the estimated 200,000 patients who are diagnosed each year with wet AMD may be eligible for PDT.

According to Paul Sternberg Jr., M.D., director of the retina section at the Emory Eye Center, "PDT uses a combination of low-level laser light with a drug to stop the macula-destroying effects of the disorder. PDT is a promising alternative to the growing number of treatments we now can offer macular degeneration patients. The therapy appears to be is safer with fewer risks than photocoagulation therapy."

AMD affects more than one-fourth of all Americans over age 75. No one knows what causes the disorder or how to prevent it. AMD affects central part of the retina or the macula, the area of sharpest sight and the part we use for reading and central vision.

The wet or exudative form of AMD -- the most blinding form -- results when abnormal blood vessels form and leak fluid and blood underneath the retina in the layer of the retina in the back of the eye called the choroid. The choroid's blood vessels, combined with tissue, can form a scar-like membrane under the retina and block central vision.

The goal of PDT is to seal leaking blood vessels and slow or stop the progression of vision loss. During PDT, the patient receives an injection of a photosensitizer drug that concentrates in the abnormal blood vessels from the choroid. A non-thermal laser light shone onto the retina activates the drug. The therapy is outpatient and patients can return to normal activities immediately, though they will need to stay out of direct sunlight for at least 24 hours. Most need repeat treatments later to enhance results.

Following treatments, patients sometimes will experience a temporary reduction of vision, which will improve over the next few weeks. Research shows that the therapy preserves or improves vision (defined as no loss of visual acuity or a deterioration of less than four acuity lines on an eye chart) in 38% of patients and slows vision loss in another 31 percent.

The Emory Eye Center was one of about 30 centers worldwide that participated in Phase III clinical trials carried out by CIBA Vision of Atlanta (QLT PhotoTherapeutics of Vancouver, Canada, makes the dye and Carl Zeiss makes the laser). The therapy is marketed as Visudyne™ therapy.