Radial Keratotomy

Radial keratotomy (RK) is a surgical procedure that reduces myopia (nearsightedness), or astigmatism (diminished focus) by changing the shape of the cornea—the outermost part of the eyeball. The procedure is particularly attractive to individuals who want to avoid wearing glasses or wish to be rid of the inconvenience of contact lenses. RK is a quick, relatively painless procedure that takes less than 30 minutes to perform; it is done on an outpatient basis. But while vision can improve immediately, the results may change, sometimes for the worse, over the following several months or years. RK was first attempted in Japan in 1939, then refined during the 1960s and 1970s in the Soviet Union, and first performed in the United States in 1978.

The cornea, the clear cover of the eye, and the lens work together to focus light rays entering the pupil onto the retina, the light sensitive tissue at the back of the eye. The cornea has a natural curve, and the greater the curvature, the greater its refractive power, that is, its ability to bend light so it focuses on the retina.

Normally, pressure inside the eyeball pushes the edges of the cornea forward slightly, flattening the central few millimeters of the cornea and reducing the amount of curvature. Candidates for RK have either excess curvature of the cornea or elongated eyeballs, both of which cause light rays to focus in front of the retina causing myopia. This makes objects at a distance appear blurry.

Astigmatism occurs when the surface of the cornea is not spherical in shape, but has an irregular contour. This makes it difficult to focus clearly on an object, causes a doubling or "ghosting" effect.

Keratotomy, which refers to cutting the cornea, corrects both of these problems by reducing the natural curve of the cornea and slightly flattening it. The reshaped cornea focuses light rays directly on, or very near, the retina, producing a sharper image.