I'm Dr. John Sheppard, associate professor of ophthalmology at Eastern Virginia Medical School. This procedure, first performed with a finely sharpened metallic blade, flattens the cornea of the eye to shorten the eye and thereby correct myopia, or nearsightedness. Modern diamond knives have perfected the operation, which can be completed in less than five minutes by an experienced ophthalmologist using only local topical eye drop anesthesia. The eye is held effortlessly open with a fine wire lid speculum, and the entire process is observed by the surgeon through a precision operating microscope. Between four and 16 radial spoke incisions are created around the central visual axis of the cornea.
Healing is rapid, and full visual recovery generally occurs within only a few weeks.
RK is only useful for mild degrees of myopia, since there is a limit to the size, number, and depth of incisions that the cornea will safely tolerate. Advantages of RK include the convenience of an office procedure, rapid recovery, a low rate of serious complications, and avoidance of tissue removal or incision directly within the central visual axis. Disadvantages include a starburst effect in dim lighting, which is a result of a large dilated pupil adapting to the dark and resultant interference by the ends of the radial incisions with light entering the eye. Other problems have included changes in vision during the course of the day due to diurnal or daily biological rhythms which naturally change the pressure of the eye. Slightly higher pressures, however normal, may cause the weakened cornea to elongate, thereby rendering the patient more nearsighted at that particular hour of the day.