Epithelial thickness mapping may help rule out keratoconus in LASIK candidates

J Refract Surg. 2009;25:569-577.

Epithelial thickness mapping may enable clinicians to perform LASIK in eyes with topographic-suspected keratoconus that would have been excluded from surgery based on different criteria, a study showed.

"Suspect keratoconus, confirmed to be non-keratoconic by epithelial thickness profile criteria, demonstrated equal stability to control eyes 1 year after LASIK," the study authors said.

The retrospective, comparative study included eyes suspected of keratoconus based on Atlas (Carl Zeiss Meditec) and Orbscan II (Bausch & Lomb) topography. The researchers also used Artemis very high-frequency ultrasound (ArcScan) to perform epithelial thickness mapping.

Keratoconus was confirmed by the Artemis in cases in which the epithelial thickness profile showed relative epithelial thinning concurrently with an eccentric posterior elevation best-fit sphere apex. Keratoconus was ruled out in cases in which examiners found a relatively thicker epithelium or did not find localized thinning over the topographical area suspected of keratoconus.

Patients underwent follow-up examinations for 1 year after LASIK. A control group comprised patients matched within 0.50 D for sphere, cylinder and spherical equivalent.

Between 3 months and 12 months postop, the suspected keratoconus group had an average change in spherical equivalent of –0.10 D; controls had an average change in spherical equivalent of –0.10 D. Study data showed no statistically significant differences between the groups in shift from 3 months to 12 months in spherical equivalent or cylinder, or change in best corrected visual acuity. No eyes lost two lines of visual acuity; 5% of keratoconus-suspect eyes and 2% of control eyes lost one line. Ectasia was not seen in either group.