The indispensable role of epithelial thickness mapping in modern corneal practice: A case-based review

Abstract

The corneal epithelium is a metabolically active layer that undergoes continuous remodeling to compensate for underlying stromal contour changes, a process that can obscure true pathology on conventional topography and pachymetry. Epithelial thickness mapping (ETM) has thus become an indispensable diagnostic modality, providing high-resolution, quantitative assessment of epithelial architecture across the corneal surface. This case-based review details the critical applications of ETM in contemporary practice. It is paramount for the early detection of subclinical ectasia, where characteristic inferotemporal epithelial thinning and the “donut pattern” of remodeling provide biomarkers with superior sensitivity, often preceding tomographic signs. ETM enhances refractive surgery safety by distinguishing true stromal ectasia from benign epithelial masking, thereby refining candidate selection. It deciphers postoperative epithelial remodeling following procedures such as laser-assisted in situ keratomileusis or photorefractive keratectomy, explaining visual outcomes and guiding therapeutic interventions. Furthermore, ETM offers objective insights into conditions ranging from epithelial basement membrane dystrophy and dry eye disease to limbal stem cell deficiency. The integration of ETM with corneal tomography and clinical examination represents a fundamental advancement in precision corneal diagnostics. It transforms our understanding from a surface-level evaluation to a layered, dynamic assessment, improving diagnostic accuracy, surgical planning, and longitudinal management across a spectrum of corneal pathologies.