Measurement Repeatability and Concordance of Corneal Tomography in Keratoconus Using Anterion Versus Pentacam

Purpose: This study aimed to compare the repeatability and agreement of corneal tomographic measurements between the Anterion Cornea App and Pentacam HR in keratoconus (KCN). Methods: Eyes with KCN were imaged three consecutive times with each device. Intra-device repeatability was assessed using intraclass correlation coefficients (ICCs), within-subject standard deviation (Sw), coefficient of variation (CV), and repeatability coefficients (RCs). Inter-device agreement was evaluated using concordance correlation coefficients (CCCs) and Bland-Altman analysis. Parameters included anterior and posterior keratometry values (K1, K2, K_mean, K_max, and ΔK), central corneal thickness (CCT), and thinnest pachymetry (TP). Results: Twenty-eight eyes from 17 patients were included. Both devices demonstrated high same-session repeatability (ICC > 0.90 and CV < 5%) for all parameters except anterior ΔK and posterior ΔK. Anterion demonstrated lower measurement variability than Pentacam for all parameters. For anterior K_max, Anterion had an RC of 1.38 diopters (D) versus 2.48 D for Pentacam. Pachymetric RCs were lower with Anterion than with Pentacam (CCT: 6.24 vs. 18.85 μm; TP: 5.93 vs. 20.34 μm). Inter-device agreement was substantial (CCC > 0.95) for most parameters except ΔK. Compared with Pentacam, Anterion measured CCT as 6.16 μm thinner and TP as 11.99 μm thinner. Bland-Altman analysis showed greater inter-device variability for all anterior keratometry parameters, posterior K1, and posterior K_mean. Conclusions: Anterion demonstrated lower same-session measurement variability than Pentacam HR, particularly for K_max and pachymetry. Future longitudinal studies across multiple sessions are needed to assess whether Anterion's lower same-session variability confers any advantages in KCN detection and progression monitoring. Overall, the two devices should not be used interchangeably for KCN assessment.