Pentacam Tomography Remains Highly Repeatable In Keratoconic Eyes Following Corneal Cross-Linking

To determine whether corneal cross-linking (CXL) alters the intra-session repeatability of Pentacam tomographic measurements and whether repeatability remains stable across post-operative timepoints and disease severity.

Retrospective observational cohort study included 268 keratoconic eyes that underwent epithelium-off accelerated CXL at a tertiary care centre (Greenlane Clinical Centre, Auckland, New Zealand) between 2021 and 2023. 

Each eye contributed one pre-operative and at least one post-operative visit with three consecutive same-session Pentacam scans. For each parameter and visit, within-subject standard deviation (Sw), repeatability limit (RP), coefficient of variation (CV%), and intraclass correlation coefficient (ICC 1,1) were calculated. Repeatability at post-operative timepoints (1, 3, 6, 12, 18, and 24 months) was compared with pre-operative values using linear regression with cluster-robust standard errors. Severity–repeatability analyses evaluated whether Sw or CV varied across TKC-defined mild, moderate, and advanced keratoconus groups. A complete-case subgroup (n = 20 eyes) was analysed as a sensitivity check. 

No statistically significant increases in Sw, RP, or CV were observed at any postoperative timepoint relative to pre-operative values (all p > 0.05). ICC values remained ≥0.90 across most parameters, indicating excellent repeatability; exceptions included KI at 3 months (ICC 0.86) and pachymetry indices at 6 months (ICC 0.66–0.83). Subgroup analyses showed similar repeatability trends, with isolated significant contrasts not replicated in the full cohort. Greater disease severity was associated with higher absolute Sw and CV, but not with differing postoperative repeatability patterns

Pentacam tomography maintains high intra-session repeatability after CXL, with no evidence of post-operative degradation up to 24 months, supporting its continued use for longitudinal monitoring of keratoconus after treatment.