Distinct corneal morphometric remodeling in early keratoconus: Insights from sirius scheimpflug-placido tomography...

This study aimed to investigate the diagnostic performance of Sirius Scheimpflug-Placido tomography parameters in distinguishing early-stage keratoconus (KC) from normal eyes and to determine whether quantitative epithelial pattern assessment adds incremental value to these measurements. In this retrospective cross-sectional study, 115 eyes were included: 80 eyes with early-stage KC (Stage 1, n = 38; Stage 2, n = 42) and 35 age-matched healthy controls. Only patients with unilateral KC were enrolled in the KC group, and the affected eye was selected for evaluation, whereas only the right eye of each participant was included in the control group. Corneal imaging was performed using the Sirius system to measure anterior and posterior curvature, pachymetry, corneal volume, anterior chamber depth, anterior chamber volume, KC-specific indices, and higher-order aberrations. Quantitative epithelial pattern assessment was conducted with anterior segment optical coherence tomography, evaluating the mean, minimum, maximum, and range of epithelial thickness within the central 6-mm zone. Anterior corneal curvature (Kmax, SimK1, SimK2) and pachymetric parameters (thinnest corneal thickness, corneal volume [Kvol]) significantly differed between keratoconic and control eyes (P < .001), with progressive changes from Stage 1 to Stage 2. Posterior corneal indices (Symmetry Index Back, Keratoconus Vertex Back, Baiocchi-Calossi-Versaci Back) showed pronounced differences, reflecting early ectatic changes. Higher-order aberrations, particularly vertical coma, increased with disease stage. Epithelial pattern assessment revealed focal thinning over the cone apex and increased range, correlating with posterior elevation and coma, highlighting subtle remodeling even in early KC. Sirius Scheimpflug-Placido tomography provides highly effective diagnostic metrics for identifying early KC, with quantitative epithelial pattern assessment serving as a supportive biomarker that refines diagnostic accuracy in ambiguous presentations. These findings highlight the clinical relevance of combining corneal morphometric and epithelial remodeling analyses for enhanced early detection of KC.