New laser role for diabetes eyed.

Using lasers on the eyes of diabetics with macular edema, a swelling of the key focusing area of the retina, can prevent a significant loss of vision in 200,000 people in the United States in the next five years, according to researchers involved in a National Eye Institute (NEI)-sponsored multicenter evaluation of the procedure.

They lased 754 eyes of people with macular edema and compared them with 1,490 nonlased eyes. After three years, only 12 percent of the treated eyes, compared with 24 percent of the untreated eyes, had suffered a significant loss of vision, they report in the December ARCHIVES OF OPHTHALMOLOGY.

Lasers are already used in diabetic retinopathy to destroy the abnormal blood vessels that grow over the retina. The new research extends the benefit of lasers to vessel growth in the macula.

In macular edema, abnormal vessels growing in the macular area leak fluid. Explains Frederick L. Ferris of the Bethesda, Md.-based NEI, "The retina absorbs the fluid like a blotter, swells up and loses its shape, so the image is distorted. It's like having wrinkled film in a camera."

Exactly how laser use stops the process isn't known, says Ferris. The suspicion is that tiny laser burns in the swollen area damage the leaky parts of the vessels, and as they heal they no longer leak. The treatment's inability to halt vision loss in about half the cases can be due to a persistence of leaking, to a loss of needed blood vessels or to other ocular diseases unassociated with the edema, Ferris says. Crucial to success is early intervention.