Diagnostic Value Of Corneal Epithelial Thickness Parameters In Keratoconus Using Anterion Oct

Keratoconus is a corneal ectatic disorder characterized by progressive corneal thinning and anterior protrusion, typically beginning in adolescence and potentially progressing over many years, often affecting both eyes. In corneal topography, keratoconus is identified by localized steepening, thinning, and marked asymmetry, reflected by combined alterations in curvature, elevation, pachymetry, and various diagnostic indices. In recent years, studies have investigated epithelial changes in keratoconus. However, there are limited studies in the literature evaluating these changes using the Anterion® (Heidelberg Engineering GmbH, Heidelberg, Germany) device.

Department of Ophthalmology, Kocaeli University Faculty of Medicine, a tertiary referral center in Kocaeli, Türkiye.

This retrospective observational case-control study included 202 eyes of 99 patients with keratoconus and 71 eyes of 39 healthy controls. Keratoconus patients were divided into early stage (Stage 1 and 2) and advanced stage (Stage 3 and 4) groups. In addition to best-corrected visual acuity (BCVA) and routine topographic parameters (Kmax, Kmean, central corneal thickness, etc.), epithelial parameters-including mean epithelial thickness, thinnest epithelial thickness, and inferior-superior (I-S) epithelial thickness difference-were recorded. Statistical analyses were performed using IBM SPSS Statistics (version 27.0). A p-value <0.05 was considered statistically significant.

Median epithelial thickness was 49 (47-51) µm in controls, 51 (48-52.75) µm in early keratoconus, and 50 (47-52) µm in advanced keratoconus, with a difference only between controls and early-stage eyes (p=0.032). Thinnest epithelial thickness was lower in advanced keratoconus (29 [20.75-34] µm) than controls (38 [36-41] µm) and early-stage disease (38 [35-41] µm; p<0.001). The I-S difference was reduced in both keratoconus groups (p<0.001). ROC analysis of the I-S epithelial thickness difference showed moderate diagnostic performance (AUC=0.711, 95% CI:0.646-0.775); at a cutoff ≤0.5 µm, sensitivity was 44.6% and specificity 87.3%.

Epithelial I–S asymmetry was significantly altered in early keratoconus compared with healthy eyes, despite preserved minimum epithelial thickness, indicating that asymmetric remodeling precedes focal thinning and represents an early structural signature of disease. In contrast, reduction in thinnest epithelial thickness appeared only in advanced stages, reflecting progression, while mean epithelial thickness showed limited discriminatory value. These findings highlight epithelial I–S asymmetry on swept-source OCT as a sensitive early biomarker, with thinnest epithelial thickness serving as an indicator of progression.