RADIAL KERATOTOMY (RK) is most effective at treating low to moderate levels of nearsightedness. It was first attempted in the 1970's by a Russian physician named Fyodorov. He discovered that placing a number of microscopic, spoke like incisions, in a "radial" pattern around the center of the cornea caused it to flatten. This flattened shape allows light to focus more directly on the retina, thereby reducing or eliminating nearsightedness.
Astigmatic Keratotomy (AK) is simply a modification of the Radial Kerototomy technique and is often performed on patients who have both nearsightedness and astigmatism. To treat astigmatism, the cornea must be made more spherical, or uniformly curved in all directions. This is accomplished by making incisions in the steepest parts of the cornea, causing it to relax and become more round. AK can be performed along with other types of refractive surgery, too.