Scientists See Ray of Light in Fight Against Blindness
Scientists are harnessing light beams to fight one of the most insidious problems of aging, providing a ray of hope against a creeping blindness that steals vision from the center out.
Age-related macular degeneration, or AMD, is the leading cause of blindness in people over 50.
First, fine detail fades. Your crossword puzzle seems OK at a glance, until you try focusing on just one word. People’s faces start to blur. You can’t read or drive. Eventually, the worst form of AMD causes blindness.
Now scientists are trying an experimental light-activated drug to help preserve patients’ eyesight. Visudyne is not a cure, cautioned Dr. Neil Bressler of Johns Hopkins University. Nothing can restore already-lost vision.
But for early-stage patients, “we may be able to slow down vision loss, or reduce the chance of [AMD] costing them any more vision,” said Bressler, who heads a nationwide Visudyne study.
And the National Eye Institute, worried that the graying of America means millions more people are at risk, is pouring $25 million into research to curb the disease. Among the work:
* An ongoing trial of 4,800 people is comparing whether vitamin C, vitamin E or beta carotene, or the mineral zinc, can stop the progression of AMD-caused vision loss.
* A government-funded study is about to enroll 350 people to see if a new type of surgery to remove a tuft of disease-caused blood vessels could stop the blindness.
* In March, the government starts a third study to see if removing drusen--yellow deposits on the retina that are a precursor of AMD--can actually prevent the disease from striking.
AMD is a budding epidemic, warns institute director Carl Kupfer: Some 1.7 million sufferers are legally blind already, and the aging population means 6 million more could go blind in 20 years.
The macula is the light-sensitive layer of tissue in the center of the retina. Two types of AMD destroy it.
“Dry” AMD, which accounts for 90% of cases, slowly breaks down the macula’s light-sensitive cells. There is no treatment. But the damage occurs slowly, so victims only gradually notice a blind spot and don’t completely lose sight.
“Wet” AMD is rarer but much worse. New blood vessels form behind the retina, leaking onto the macula and destroying it. Straight lines look wavy. Then sufferers suddenly develop a central blind spot that often progresses to blindness within two years.
Research focuses on wet AMD.
There is one treatment, a laser that cauterizes the blood vessels. But only 15% of patients qualify because, if the blood vessels are in the wrong spot, the laser can hurt more than it helps.
Visudyne works differently. The light-activated drug is injected into the arm and migrates into the eye’s abnormal blood vessels. Shine in a non-burning beam of light and the drug “switches on,” eliminating those blood vessels without hurting surrounding tissue.
In a study of 600 patients, 61% given Visudyne had stable or slightly improved vision after a year, vs. 45% of patients given a placebo. The study is continuing another year, important because more-rapid vision loss usually occurs in wet AMD’s second year.
But manufacturer QLT Phototherapeutics is about to ask government permission to sell Visudyne based on the early data, approval that Bressler expects by 2000. Until then, the Visudyne trials are full and anxious patients will have to wait.
People over 40 need regular eye exams, with eyes dilated, to hunt for signs of disease. AMD sufferers and those at risk should ask an ophthalmologist about new treatments, Bressler advised.
A small radiology study presented last month suggests two weeks of low-dose radiation might help wet AMD too, although Kupfer cautioned that better studies are needed.
