How do ophthalmologists correct nearsightedness in ten minutes with radial keratotomy?

In 1974, a Soviet ophthalmologist named Svyatoslav Fyodorov developed a surgical procedure that has proved a speedy and sometimes very effective method for correcting nearsightedness.

The basic idea is to alter the curve of the cornea, which is the window into the eye, by means of tiny surgical scars. Performed under local anesthesia, the procedure, called “radial keratotomy,” usually takes a half an hour, but some doctors claim to do it even faster.

It costs about $2,000 for each eye, and the patient can go back, with a patch and some discomfort, to what he was doing that day.

Here’s how it works.

A person with nearsightedness sees blurry images because his cornea is too convex, causing light rays to focus in front of, rather than on, the retina in the back of the eye.

To correct that condition, an ophthalmologist uses a diamond-bladed knife and a microscope to make four to sixteen very small incisions that look like a perfect star burst on the cornea. As the tissue heals, the cornea flattens, so that without the aid of glasses or contact lenses it now brings light rays to a focus where they should be.

Doctors do worry about complications with this procedure, because it tampers with otherwise perfectly healthy eyes. The worst possible scenario is an infection in the scars called bacterial keratitis, which, if unchecked, could result in a complete loss of sight. More likely is the possibility of overcorrecting the curve of the cornea so that it focuses light behind the retina.

In such in stances, the patient actually becomes farsighted. Still another problem is that, while the results of the operation are evident soon after surgery, the cornea actually requires four or five years to heal completely. It is therefore hard to predict exactly how the cornea will finally be shaped.

One extensive study, funded by the National Eye Institute and begun in 1980, tested the eyesight of 435 patients, 99 percent of whom had 20/50 vision or worse. Highly skilled and well-trained ophthalmologists performed radial keratotomy on one eye of each of the patients.

Three years after surgery, 51 percent of the eyes that had undergone the procedure could see with 20/20 vision or better, with the moderately nearsighted patients having the best results. But 16 percent were farsighted by more than a diopter (a unit of measurement of refractive power). And 26 percent of the eyes were “undercorrected”: still nearsighted by more than a diopter. Some patients found they could no longer tolerate contact lenses, though they still needed them. Some experienced a halo-like glare at night from the scars, and some reported fluctuations in their eyesight from morning to night.

Still, if you are nearsighted you can probably understand why many patients in this group were satisfied with even imperfect results; the surgery left them less dependent on corrective lenses than they had been before. About three quarters of the whole group opted for the same surgery on the second eye.

A new technique using a computer-controlled laser beam in stead of a diamond knife is being explored. Photorefractive keratectomy” may be a more precise method than its forerunner, but the jury is still out.

In either case, some doctors are suggesting that people wait a few more years before ditching their glasses, until both techniques are better known.