Hydration effects on corneal topography.

Abstract

To evaluate the effect of corneal thickness changes on the central and paracentral corneal topography in de-epithelialized eye-bank eyes at various stages of hydration. Corneal topography of 12 eye-bank eyes was measured with a videokeratoscope at the following four stages of hydration: prethinning (mean pachymetry, 0.88 mm), postthinning (0.55 mm), after 15 minutes of rehydration (0.60 mm), and after 30 minutes of rehydration (0.64 mm). Corneal thickness changes were significant between each stage of hydration (P < .05 by repeated-measures analysis of variance). No net astigmatic shifts were observed between any stage of hydration (P = .45). From prethinning to postthinning, dehydration produced average central corneal steepening of 0.44 diopters (P < .001), and average paracentral steepening of 0.89 D (P < .001). Significant changes in corneal power were not measured during normal rehydration until 30 minutes posthydration, when the central cornea had flattened an average of 0.3 D from normal thickness (postthinning) levels (P < .05). Substantive thinning of corneal tissue caused statistically significant but clinically minimal ( < 1 D) central and paracentral steepening, but smaller corneal hydration changes that can occur during experimental and surgical procedures had little effect on corneal topography.