Repeatability of Epithelial Thickness Mapping in Normal and Keratoconus Eyes Using a Novel Hybrid Scheimpflug—Optical Coherence Tomography Device

PURPOSE: A novel diagnostic device combining Scheimpflug and anterior segment optical coherence tomography promises increased accuracy in corneal diagnostics. The aim of this study was to analyze the epithelial thickness measurement repeatability in healthy and keratoconus eyes and define severity-dependent thresholds. METHODS: This prospective, cross-sectional, observational, monocentric study included a total of 217 eyes of 217 subjects divided into a keratoconus group (166 eyes of 166 subjects) and a healthy control group (51 eyes of 51 subjects). Keratoconus diagnosis and stage was established using multimodal imaging. Three measurements were performed with the novel combined Scheimpflug and optical coherence tomography device (Pentacam Cornea optical coherence tomography) on the same day. Repeatability coefficients (RCs) with two-sided 95% confidence intervals (CIs) were calculated for epithelial parameters. The repeatability was compared between groups and according to keratoconus severity and crosslinking status. RESULTS: The median repeatability of the epithelial thickness was slightly better in the healthy group (RC = 3.3) compared with the keratoconus group (RC = 3.9; P < 0.001) when the tear film was excluded. The overall median repeatability with (RC = 3.7) and without tear film (RC = 3.8) did not differ significantly (P > 0.05). Repeatability worsened significantly in severe keratoconus stages (P < 0.01), whereas crosslinking status had only a marginal effect. CONCLUSIONS: The hybrid tomographic device demonstrated high intrasubject repeatability for epithelial thickness assessment in healthy and keratoconus eyes, supporting its technical feasibility for clinical use. Further studies are needed to analyze the benefit of incorporating epithelium into established keratoconus scores using the hybrid system.