A high resolution photokeratoscope using digital video image acquisition and computer graphics was used to describe anterior corneal topography before and after radial keratotomy. After radial keratotomy, the entire cornea is flattened, but this effect is more pronounced centrally. The flat central “optical zone” varies in size, shape, and location. Regional variations in corneal power may explain phenomena observed after radial keratotomy, such as visual acuity that is better than would be expected on the basis of refractive error, and the occurrence of ghost images.
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