Measurement of refractive, wavefront, topographic, and keratometric changes attributable to epithelial removal in keratoconus

Abstract

ObjectiveThe corneal epithelium is able to mask topographic and keratometric abnormalities of the underlying Bowman layer in keratoconus, but its contribution to refractive and wavefront parameters has not yet been studied. This study compared the refractive and aberrometric features of the corneal epithelium and Bowman layer in eyes with keratoconus before and after epithelial debridement. MethodsCorneal refractive and wavefront variables were measured in patients with keratoconus undergoing corneal crosslinking—immediately before and after epithelial debridement using a third-generation combined corneal topographer, autorefractor, and aberrometer. ResultsAfter epithelial debridement, there were significant changes in spherical equivalent (−1.37 D; p < 0.01) and asphericity (−0.64; p = 0.03). The mean difference in the magnitude of epithelium-induced astigmatism in the 3rd and 5th central millimeter rings was 0.44 ± 3.20 D × 8 and 0.43 ± 2.75 D × 21 (positive cylinder), respectively. Corneal astigmatism axis shifted in the against-the-rule orientation after epithelial debridement. There were no significant changes in any corneal higher-order aberration parameter after epithelial debridement (p > 0.05). ConclusionsIn eyes with keratoconus, epithelial debridement increased the magnitude of anterior corneal prolateness and tended to increase astigmatism and shift its axis toward the against-the-rule orientation. This study supports the notion that the corneal epithelium smooths underlying Bowman layer irregularity in keratoconus.