A controversial eye operation to correct nearsightedness improves vision in most recipients. Almost two-thirds of those who have the surgery on both eyes are able to get rid of their glasses, according to the largest and longest-running U.S. study of the new procedure. But because surgeons cannot accurately predict how well the operation will work in an individual patient, it is not recommended for everyone, said George O. Waring, a professor of ophthalmology at Emory University School of Medicine and director of the study.
About 11-million Americans are moderately nearsighted and are potential candidates for radial keratotomy, according to the report in today's issue of the Journal of the American Medical Association.
A surgeon performing radial keratotomy makes four to eight fine cuts, arranged like the spokes of a wheel, partway through the cornea, the clear tissue covering the front of the eye. The cuts weaken the cornea, and as it heals it changes shape, becoming flatter. As a result, it tends to focus light farther back in the eye than before, sharpening the image on the retina and improving vision in a nearsighted person.
Of 435 patients who underwent radial keratotomy in the multihospital study, 69 percent had visual acuity of 20-200 or worse before surgery in the eye that received the operation. Four years after surgery, 76 percent had visual acuity of 20-40 or better, and only 2 percent had visual acuity of 20-200 or worse.
But because the amount of correction is unpredictable, surgeons cannot guarantee a patient that the operation will work as hoped.
"It's not a crap shoot. We can certainly give patients pretty good odds," Waring said, adding that results are best in younger patients who are mildly to moderately myopic, or nearsighted. For instance, a 25-year-old with mild myopia "would have a 90 percent chance of seeing 20-40 or better and going without glasses," he said.