Science / Medicine : New Surgical Technique Offers Vision of Better Sight : Science: Laser operation is designed to reshape the cornea sufficiently to correct nearsightedness. So far, results have been 80% to 90% successful.

Alan McMillen walked to his surgery looking confident, even eager. After he stretched out on the well-padded gurney, his surgeon, Dr. James Salz, positioned a computer-assisted laser overhead.

Slowly, Salz directed the light beam into McMillen’s right eye, gently firing the laser again and again. In 30 seconds, it was over.

In that brief time, Salz had sculpted away 40 microns, or less than 10%, of the surface of the cornea, the eyeball’s transparent outer coating. If successful, the surgery will reshape the cornea sufficiently to correct McMillen’s vision to a perfect 20/20.

Nationwide, doctors are nearing the two-year mark in their study of this surgery, called photorefractive keratotomy r PRK, for nearsighted patients. Overall, they are giving it high marks to correct slight and moderate nearsightedness, but caution that it won’t be a cure-all.

The new laser has the most appeal for those weary of contact lenses or eyeglasses and workers who need perfect vision for occupational reasons, says Salz of Cedars-Sinai Medical Center in Los Angeles. If long-term results of PRK surgery continue to be favorable, Salz predicts that a growing number of the 70 million nearsighted Americans who wear eyeglasses or contact lenses will seek the surgery.

In nearsightedness, the cornea is abnormally shaped so that light rays entering the eye land in front of the retina--rather than precisely on it--where visual images are picked up. PRK flattens the cornea just enough to ensure that the light rays land on the retina.

In all, 2,400 nearsighted patients will undergo PRK surgery during the investigational study, now in its final phase at about 25 centers nationwide. Depending on geographic location, patients pay $1,200 to $2,000 per eye for the surgery. So far, results have been 80% to 90% successful, say officials for VisX Inc. and Summit Technology, the manufacturers of the laser systems used for the surgery. The laser systems, which cost $250,000 to $400,000, work without heat and do not injure surrounding tissue.

Twelve of 13 patients who had PRK performed by Salz and his colleagues at Cedars-Sinai Medical Center, for instance, had visual acuity of 20/30 or better at their four-month follow-up exam. Since surgery, the vision of McMillen--who is president of VisX--has improved to 20/15 without eyeglasses or contact lenses. Dr. Robert Fenzl of Garden Grove says 80% of his 12 PRK patients, with follow-up periods up to a year, are seeing 20/40 or better--generally considered good enough to do without eyeglasses or contact lenses.

Some eye doctors contend that PRK will eventually replace radial keratotomy (or RK), the surgery imported from Russia more than a decade ago. In radial keratotomy, a scalpel is used to make incisions in a radial pattern, flattening the cornea to a more normal shape. But the incisions weaken the structure of the cornea, sometimes resulting in unstable vision.

Advocates of PRK say the new laser surgery promises more consistent results than RK. Moreover, before performing PRK, a surgeon enters data about a patient’s nearsightedness into the computer, which computes the amount of corneal resculpturing necessary. A dry run is done on a small piece of plastic. There is no dry run before RK surgery.

The PRK surgery is painless, thanks to topical anesthesia. But postoperative pain for a day or more is typical, doctors and patients say.

“During the healing process, patients may have some fluctuation of vision or night glare,” adds Dr. George O. Waring III, director of refractive surgery at Emory University who is also studying PRK.

PRK probably won’t be generally available for at least two more years and, even then, it won’t be the solution for every nearsighted person. It does not usually work well, doctors say, for severe nearsightedness, which require glasses or contact lenses.

One voice of caution is Dr. Walter Stark, professor of ophthalmology at Johns Hopkins University School of Medicine and a consultant to the ophthalmic devices panel of the Food and Drug Administration, which reviews data on the procedure.

“The data submitted to date are encouraging,” Stark says. But it is too soon to say conclusively whether the results “demonstrate safety and efficacy for correction.”

“In radial keratotomy,” Stark says, “some problems became apparent three to five years postoperatively.”