Radial keratotomy flattens the cornea, but in a nonuniform fashion. We used computer-assisted topographic analysis to examine curvature changes in different regions of the cornea. Within 45 days after surgery in human eyes, the central and midperipheral cornea flattens and the periphery steepens. Shortly after surgery, the central cornea (within 1-1.5 mm of the corneal light reflex) is steeper than the adjacent midperipheral cornea (1.5-3 mm peripheral to the light reflex). With time, however, the central cornea flattens more than the midperiphery, such that it is no longer relatively steeper. This regional variability in corneal curvature after radial keratotomy helps explain phenomena such as multifocal lens effect after radial keratotomy, and the changes with time account for the conflicting results observed clinically in human corneas and experimentally in human eye bank eyes.
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