The clear covering of the eyeball is called the cornea. Nearsighted people have to wear glasses or contact lenses to see well at a distance. Without their glasses, they can see up close. Farsighted patients are bothered initially at reading distances, and the problem gradually worsens until it affects driving. Laser surgery may be performed to change the shape of the eye to correct for distance vision.
The best candidates for this type of surgery are people with corneal conditions whose vision cannot be corrected by wearing glasses or contact lenses. Many people also choose to have corneal surgery for convenience and for cosmetic reasons.
One of the first refractive surgery procedures was called radial keratotomy (RK). This operation consists of spoke-like cuts in the edges of the cornea. The cuts do not extend over the area covering the pupil. The cuts allow the edges of the cornea to weaken and bow. This causes the area of the cornea over the pupil to flatten and decreases the person's nearsightedness.
While this operation is still performed today, it has been almost completely replaced in the United States by a procedure called LASIK. LASIK, or laser in situ keratomileusis, is usually done on both eyes at once. It can be used to correct farsightedness and nearsightedness, with or without astigmatism.
In this technique, a thin flap of the cornea is lifted. Then a laser is used to dissolve very thin layers of corneal tissue under the flap and create a flatter surface over the pupil. After the laser treatment, the flap is repositioned.
Other methods for reshaping the cornea are also under investigation. One of these involves the use of a peripheral corneal ring. Also, a technique for implanting an artificial lens in the eye to correct vision problems shows promise as an alternative to LASIK.
The Merck Manual of Medical Information, Home edition, 1997