Inter-expert agreement on epithelial thickness mapping for refractive surgery screening: variability highlights need for standardization

Purpose: To evaluate inter-expert agreement on epithelial thickness map interpretation and its influence on eligibility decisions for keratorefractive surgery candidates. Setting: Multicenter international collaboration involving four experienced refractive surgeons. Design: Retrospective, masked case review study. Methods: A total of 103 cases were retrospectively evaluated, including patients with normal (n=44), borderline (n=44), and keratoconic (n=15) corneal tomography, as defined by the Belin-Ambrosio-Display (BAD). Four independent experts (MD, JA, AS, NL) first assessed surgical eligibility based on Scheimpflug tomography and subsequently re-evaluated the same cases with the addition of anterior segment OCT–based epithelial thickness maps. To ensure comparability, a standardized questionnaire with nine predefined epithelial thickness characteristics was used. Inter-rater agreement was quantified with Fleiss’ kappa (κ), and the relative impact of each imaging modality on decision-making was ranked. Results: Incorporating epithelial mapping changed the eligibility decision in 19% (77 / 412) of cases. Specifically, 9% (16 / 176) of normal, 20% (35 / 176) of borderline, and 3% (2 / 60) of keratoconic cases were reclassified as eligible, while 2% (3 / 176), 6% (10 / 176), and 3% (2 / 60), respectively, were deemed ineligible. Inter-rater agreement on eligibility was moderate before (κ=0.46) and after (κ=0.43) adding epithelial maps but remained poor in borderline cases (κ=0.14 and 0.12, respectively). Agreement on epithelial profile features ranged from poor to fair (κ=−0.78 to 0.35). Corneal topography and BAD were ranked as most influential, followed by epithelial mapping. Conclusion: Epithelial mapping frequently shifted decisions toward eligibility. However, poor inter-expert agreement highlights the need for standardized, safety-oriented interpretation to ensure consistent ectasia risk assessment prior to refractive surgery.