Optical zone diameters for photorefractive corneal surgery.

PURPOSE To examine the physiological optics of photorefractive corneal surgery and to study the effect on glare production of the optical zone diameter. METHODS An optical analysis computer program was used to generate rays that define the edge of the optical zone for any given pupil size and glare-free field. RESULTS The optical zone diameter must be based on the postoperative corneal curvature because the determines magnification of the pupil. The minimal optical zone diameter of uniform optical power was determined both for myopic and hyperopic surgery and for two values of anterior chamber depth. CONCLUSIONS Optical zone diameters must be at least as large as the entrance pupil diameter to preclude glare at the fovea, and larger than the entrance pupil to preclude parafoveal glare.