Agreement between Sirius Scheimpflug-Placido tomography and Anterion swept-source OCT in keratoconic eyes stratified by prior corneal cross-linking: a retrospective cross-sectional agreement study.

AIM: This study aims to assess the agreement between the Scheimpflug-Placido tomographer (Sirius) and the anterior-segment swept-source optical coherence tomography (Anterion) in evaluating anterior segment parameters separately in keratoconus (KC) patients with and without corneal cross-linking (CXL). METHODS: A retrospective analysis was conducted on 108 eyes of patients with keratoconus (KC), divided into two groups according to previous corneal collagen cross-linking (CXL) status: eyes with prior CXL (wCXL group, n = 72) and eyes without CXL (woCXL group, n = 36). Evaluated parameters included anterior and posterior keratometric measurements, pachymetric measurements, anterior chamber parameters, corneal astigmatism, and corneal shape/elevation-related indices. Measurements from both devices were compared using Bland-Altman analysis, assessing fixed and proportional biases. Agreement between devices was interpreted based on the combination of absence of significant fixed bias, absence of proportional bias, and the width of the 95% limits of agreement (LoA). RESULTS: In the wCXL group, anterior astigmatism (ant-Ast) and anterior best-fit toric ellipsoid (ant-BFT) demonstrated the most favorable bias characteristics. In the woCXL group, ant-Ast, ACD, posterior K1, and posterior Kmean showed favorable bias characteristics. CONCLUSIONS: Although ant-Ast and ant-BFT in the wCXL group and ACD, ant-Ast, posterior K1, and posterior Kmean in the woCXL group demonstrated no statistically significant fixed or proportional bias, the relatively wide LoA do not support interchangeable use of Sirius and Anterion for these measurements.