Corneal epithelial thickness profile in the diagnosis of keratoconus

To illustrate the hypothesis that epithelial thickness profile maps could be used as an adjunctive tool to improve the sensitivity and specificity of keratoconus screening by presenting a case series of examples.

The Artemis very high-frequency digital ultrasound arc-scanner was used to obtain epithelial thickness profiles in addition to a comprehensive ophthalmic examination to screen for keratoconus. Five case examples are presented; a normal eye, an eye with advanced keratoconus, and three cases where a diagnosis of keratoconus was uncertain based only on the ophthalmic examination.

The epithelial thickness profile in the normal eye was slightly thinner superiorly, consistent with that previously described for a normal population. The keratoconic eye demonstrated an epithelial doughnut pattern of epithelial thinning over the cone surrounded by an annulus of epithelial thickening. In case 1, an epithelial doughnut pattern confirmed the presence of keratoconus in an eye with an abnormal front surface topography. In case 2, the absence of an epithelial doughnut pattern excluded a diagnosis of keratoconus in a patient with an abnormal front surface topography. In case 3, the presence of an epithelial doughnut pattern coincident with an eccentric posterior elevation best-fit sphere indicated a diagnosis of keratoconus. The epithelium appeared to have compensated for the stromal surface cone, resulting in an apparently normal front surface topography.

An epithelial doughnut pattern appears to indicate the presence of an underlying stromal cone; the lack of an epithelial doughnut pattern would indicate that an abnormal topography was not due to keratoconus. In very early keratoconus, epithelial compensation can mask the presence of an underlying cone on front surface topography, ie, a diagnosis of keratoconus might be missed.