EYE CARE: HOW DOES RADIAL KERATOTOMY HELP IN MYOPIA?
The operation known as radial keratotomy (and commonly abbreviated "RK") is performed by microsurgery to correct usual myopia and sometimes high myopia. Its technique is precise and the result is unique.
Corrective lenses work for nearsightedness by changing the angle of the entering light rays so that they come to a focus on the retina. RK seeks the same end, but by a different mechanism: by changing the curvature of the cornea.
The curvature change is carried out under local anesthesia, merely using a liquid anesthetic dropped on the eye. The patient remains alert or he or she may choose to be sedated with a tranquilizer. Only one eye is operated on at a time; the other may be done two to three weeks later. The eye is kept open during surgery with a delicate clamp. There is no pain, no bleeding, and the slowest surgeon could take as long as twenty minutes to complete the entire operation. An RK finished in ten or twelve minutes is standard.
The operator marks the cornea with a special instrument to outline the visual center, which is left untouched, and a tiny sort of cookie-cutter tool with eight spokes radiating like the spokes of a wheel is pressed into the cornea to produce indentations the surgeon can follow to make his incisions.
Working with the aid of a microscope and using a tiny diamond blade with a guard to gauge the depth of incision, the doctor makes tiny cuts from the center outward. The length of such micro-incisions vary from case to case and don't fully penetrate the cornea, only about three-fourths of its thickness, depending on the degree of the patient's myopia. By cutting from seventy percent to ninety percent into the cornea's half-millimeter depth, the corneal tissue becomes weakened. Internal eye pressure then causes the edge of the cornea to bulge slightly, which flattens the central area. Thus, the visual center drops after surgery, resulting in improved vision.
After the operation, antibiotic drops are used and the eye is patched, to remain so for twenty-four hours. Healing of the epithelium takes place within this time. The sensation of an irritated eye may persist for two weeks or so, but reportedly is not particularly troublesome. Most RK patients return to work a day or two after the operation.
With the change in curvature, the corrected cornea bends the light rays at a new angle. The result is improved vision because images now are focused farther back, on the retina. The operation may take place in the ophthalmologist's office; hospitalization is not required. The degree of permanent correction achieved is usually evident by the third postoperative month. Follow-up examinations are carried out to monitor the patient's corneal measurements and to note how the eye is responding.
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