The purpose of this study was to evlauate the ability of the cornea to adapt to and maintain an induced flattening. That is, which cornea is more likely to maintain an induced flattening longer, a cornea that readily flattens or one that is more resistant? The aim was also to develop a clinically feasable test to predice the suitability of a given patient for orthokeratology. We selected twenty low myopes who had healthy corneas, minimal astigmatism, and no recent history of rigid contact lens wear. Baseline corneal maps were taken with the EyeSys and acuities were recorded. The cornea of one eye was applanated three millimeters inward with a Tonomat endplate and held in place for ten seconds. Immediately following applanation, acuities and another map were taken; then again at five, ten, and fifteen minutes. The baseline map and acuity were compared to each of the four post-applanation maps and acuities and analyzed for patterns. The group of subjects as a whole did not show significant change in K values pre- versus post-applanation. An improvement in acuity was seen in most of the subjects at some point, but in a variety of patterns. The group was broken down into smaller groups that displayed similar patterns. No statistical significance in average K values over time could be shown. There was statistical significance seen in visual acuities over time, although these changes could not be statistically linked to any change in K values. As clinically applied to orthokeratology, our study suggests the following: 1) A provocative test such as minor indentation of the cornea (perhaps with a Goldmann probe or a flat trial contact lens) may be a useful procedure for assessing short term pliability of the cornea. 2) Different corneas respond differently, suggesting that orthokeratology may never be successful on all potential candidates. 3) Visual acuity change is a better indicator of potential success than corneal curvature changes. 4) Individuals who show improved or stable short term acuity improvements may be good ortho-k patients.
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