Surgery to cure myopia linked to farsightedness

October 13, 1994|By Jonathan Bor | Jonathan Bor,Sun Staff Writer

People who hope an increasingly popular operation called radial keratotomy will reduce or even cure their nearsightedness stand a good chance of needing glasses for a new problem -- farsightedness.

A 10-year study sponsored by the National Eye Institute found that the operation, in which surgeons make spoke-like incisions to flatten the eye, usually succeeds as a treatment for nearsightedness: 70 percent of the patients no longer needed glasses or contacts for distance vision.

But many of the eyes continued to flatten in the years after surgery -- sometimes to the point of becoming farsighted. The study found that about a third of the eyes progressed this far.

"People have to weigh the benefits of avoiding wearing glasses or contact lenses against the risk of some sort of a delayed problem," said Dr. Peter J. McDonnell, an ophthalmologist with the Doheny Eye Institute of the University of Southern California and the study's co-chairman.

"Based on these findings," he added, "it may be that some people will be pleased with their vision shortly after having RK, but their opinion may change five, 10 or 15 years down the road.

The Eye Institute also found that the operation was "reasonably safe." A small percentage of people discovered that their corrected vision -- their acuity with glasses -- was actually worse than it was before surgery. And none of the people became blind from complications.

Pioneered in the Soviet Union, radial keratotomy was first offered in the United States in the late 1970s. But its popularity has exploded in recent years, with a quarter-million operations performed last year, compared with 30,000 just five years earlier.

Although many surgeons eschew advertising, some have promoted radial keratotomy with lavish advertisements in magazines, newspapers and even direct mailings.

People become nearsighted when the eye is too long from front to back. While they do not need glasses to focus near, their distance vision is fuzzy without the aid of glasses or contact lenses. In radial keratotomy, surgeons cut a series of shallow incisions that radiate like spokes from the center of the cornea, the clear round membrane that covers the front of the eye. A small area in the center, however, is left untouched.

As the incisions heal, the eye flattens slightly. This shortens the distance from the lens to the cornea, enabling the eye to focus more clearly on distant objects.

The study, appearing in this week's Archives of Ophthalmology, has been watched closely by eye specialists across the country who have been engaged in a debate over the procedure's safety and effectiveness.

To provide data, clinicians periodically examined the eyes of 435 people at nine institutions -- recording not the immediate and long-term effects of surgery. They found:

* Eighty-five percent of eyes could see 20/40 or better, the acuity required to pass the visual portion of a driver's test. Although some of the people needed glasses for selected purposes, such as reading distant signs, 70 percent of the patients said they saw well enough to shun glasses and contacts.

* Three percent of the patients actually had poorer "corrected vision" -- their vision with glasses -- after surgery.

* After the incisions healed, 43 percent of the eyes continued to change shape in the direction of farsightedness. Because surgery does not always rid patients of their nearsightedness, the change sometimes caused people to see better over time. But 36 percent of the eyes progressed enough to become farsighted.

Dr. Dimitri T. Azar, an ophthalmologist with the Johns Hopkins Wilmer Eye Institute, said the study proves the point he has been making for years: Surgeons shouldn't try to cure nearsightedness but should undercorrect so the eye has room to change shape without becoming farsighted.

"Perfect vision should not be our goal after radial keratotomy," Dr. Azar said. "I've operated on doctors who were very pleased to be undercorrected to a degree, but some people will not accept this."

Dr. Azar said he informs all prospective patients that he undercorrects, and while they will probably see better than before, they may need glasses for some purposes. Hearing this, about half the patients decide against surgery.

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