A new, laser-activated treatment for one of the most prevalent causes of blindness in people older than 60 -- macular degeneration -- will be available soon at offices of U.S. eye doctors.

On Thursday, the U.S. Food and Drug Administration announced approval for "Visudyne" therapy. It is the first treatment to slow vision loss in people with "wet, age-related macular degeneration," said an FDA spokesman. Called AMD, it is a disease of the retina and causes severe and irreversible vision loss.

Visudyne therapy, relatively painless, takes about 20 minutes, and can be performed in a doctor's office. But the cost is expected to be about $2,000 per treatment, according to a Canadian firm, QLT PhotoTherapeutics, which makes the drug to fight AMD. Five treatments over two years may become standard.

"Until now, there was no adequate treatment for patients affected with the wet form of AMD," said Dr. Jane E. Henney, FDA commissioner. "However, this new therapy will help slow the vision loss for the many patients who face losing their vision to this debilitating condition."

"The success of Visudyne is based on stopping the progress of this devastating disease," said Steve Lang, a vice president of CIBA Vision, Atlanta. CIBA is part of the Swiss firm, Novartis AG, which developed Visudyne with QLT.

Lang said CIBA began Wednesday to ship the product, and it should be available soon at the offices of ophthalmologists.

Wet AMD is caused by the growth of abnormal leaky blood vessels that eventually damage the macula. It is "the area of the eye responsible for central vision which is essential for most visual activities, including reading, driving, and recognizing faces," said the FDA spokesman.

The central field of vision is affected in varying degrees, while the peripheral or side vision is usual with wet AMD and untreated will become functionally blind within two years.

Visudyne, injected intravenously into the patient's arm, travels throughout the body including the abnormal vessels in the eye. Next, the drug is activated by shining a laser light into the patient's eye for approximately 90 seconds, said the FDA spokesman. While 90 percent of AMD is the "dry" form and only 10 percent is the "wet" form, the "wet" form destroys vision more quickly.

Visudyne therapy slows retinal damage but does not stop the vision loss or restore vision in eyes that have been damaged by AMD, according to the FDA.

Clinical trials, involving 609 patients at 22 centers in North America and Europe, showed that patients treated with Visudyne therapy were more likely to have stable vision compared to placebo-treated patients at 12month follow-up examination. Vision was stabilized in 61 percent of patients treated with Visudyne therapy compared to 46 percent of patients administered placebo.

Medicare is expected to cover most of the cost for elderly patients receiving the Visudyne treatment.The treatment is being used in Switzerland and Malta, and other European countries probably will soon approve its use.