Evolution of radial keratotomy for myopia.

The basic principles of radial keratotomy for myopia were described in 1898: radial incisions flatten the cornea in the direction of the incision, deep incisions were more effective, and some of the result diminished as the cornea healed. Since then the surgical procedure has undergone evolution and refinement, with changes now occurring rapidly. The acronym STEPS provides a useful guide in evaluating the operation: safety, technique of surgery, efficacy, predictability, stability, and each of these subjects will be discussed.