Epithelial Mapping Efficacy for Subclinical Keratoconus Identification.

Purpose: To evaluate the utility of automated epithelial thickness metrics to identify subclinical keratoconus (SKC) through epithelial thickness pattern comparisons between normal controls, (SKC), and manifest keratoconus (KC).

Design: Retrospective cross-sectional study METHODS: There were 200 eyes from 200 patients evaluated, including: (1) 100 control eyes from 100 patients with bilaterally normal corneal topography/tomography and slit-lamp examination (controls); (2) 50 eyes from 50 patients with SKC; (3) 50 eyes from 50 patients with KC. Epithelial mapping was performed using anterior segment optical coherence tomography (AS-OCT) imaging (Avanti RTVue XR, Optovue). Area under the receiver operating characteristic (AUROC) curves were used to determine the overall discriminative accuracy of the significant test parameters as described by the area under the curve (AUC) and to calculate the sensitivity and specificity of each parameter.

Results: There were no differences between control and SKC groups in any regional OCT epithelial thickness parameter (p>0.05 for all). Among relational epithelial thickness metrics, only superonasal - inferotemporal (SN-IT) value differences reached statistical significance between control and SKC groups (-0.81 μm vs. 0.41 μm, p = 0.003), but this metric still showed limited performance in differentiating groups (AUROC = 0.68). Most stromal thickness values were significantly different between SKC and controls (p<0.001 for all).

Conclusion: Epithelial thickness patterns were not effective as a primary metric to identify subclinical keratoconus. Scheimpflug metrics and regional stromal thickness values significantly outperformed epithelial metrics in differentiating both SKC and KC eyes from controls. Epithelial mapping metrics thus appear significantly less sensitive than predicted for subclinical keratoconus detection in early disease manifestations.