UNIVERSAL CITY, Calif. -- A newly developed laser technique being tested at the Johns Hopkins Hospital Wilmer Eye Institute in Baltimore could open the way to therapy for a previously untreatable eye disease that afflicts millions of elderly people.
Until recently, laser therapy was used to treat only select cases of the disease, "occult" macular degeneration, the leading cause of blindness in people over age 65.
More than 75 percent of patients who suffer a hidden form of the disease could not be helped.
The new technique, which uses the laser to place an array of spots in a scatter pattern in the macula -- the central part of the retina -- is still under investigation.
Wilmer and Hopkins School of Medicine researchers should know within a year whether it can prevent or delay visual deterioration, Dr. Neil M. Bressler said yesterday.
"The results of this study could have profound effect on millions of the elderly at risk of going blind from macular degeneration over the next several decades," Bressler, one of the researchers, told a science writers' seminar sponsored by Research to Prevent Blindness.
In the select classic cases, ophthalmologists can clearly identify the exact extent of abnormal blood vessels which develop as a result of some thickening in the outer layer of the retina that lines the back inside wall of the eye.
And, eye specialists know exactly where to obliterate the retina with the laser to destroy the abnormal vessels to prevent them from growing and causing a large scar to form in the macula, the Wilmer researcher said.
The macula allows a person to see fine details -- to read small print, thread a needle, read the time on a watch.
If both eyes are affected by macular degeneration, a person will be legally blind, which means the central visual acuity will be 20/200 or worse -- the person can see at 20 feet what those with normal vision can see at 200 feet. But, peripheral, or side vision, remains unaffected.
Most patients who are at risk for developing scarring have occult, or poorly defined abnormal blood vessels with a diffuse oozing of fluid throughout the macula, Bressler said. In almost 50 percent of these patients, severe visual loss will develop within two years.
"We cannot pinpoint where obliterative laser treatment should be applied, so we have decided to contain rather than destroy the abnormal vessels in the occult form of the disease," the researcher further said.
Based on laboratory studies by former Hopkins associates at Wilmer, the researchers hypothesized that placing an array or a grid of laser burns to the macula of eyes with hidden abnormal vessels might allow them "to stimulate changes in the scarring of the macula."
That was the basis for a pilot study that began two years ago to test the new laser technique on patients with occult macular degeneration, Bressler said.
Since then, 53 patients have had the option to take part in the trial comparing the efficacy of grid laser treatment to no treatment in preventing severe visual loss.
Bressler described the 15-minute treatment as "relatively painless." All treated or untreated patients are followed periodically for up to two years to determine whether visual loss develops more often in the treated or untreated group.
So far, the study has shown that the treatment can cause resolution of leakage of fluid and/or blood from abnormal vessels within six weeks in some cases. Rapid resolution of fluid without laser treatment has been documented only rarely, according to Bressler.
"But this does not necessarily imply that eyes which are treated will have better vision than eyes not treated," he said. "Patients will want this treatment only if it prevents visual loss."
Within a year, he will know the visual outcome in the treated group or untreated study patients, he said. And, if there is a trend toward a better visual outcome in the rested group, research funds will be sought to support a multicenter trial involving 300 to 500 patients.