Purpose: To study the relationship between central epithelial thickness (CET) and central corneal thickness (CCT) in healthy individuals and to evaluate their changes after laser in situ keratomileusis (LASIK).
Methods: In this study, we included 150 patients (150 eyes) who underwent LASIK and 83 healthy individuals (83 eyes). In all patients, CET and CCT were measured using anterior segment optical coherence tomography with Copernicus REVO on B-scans. Statistical analysis was performed using the Spearman rank test, t test, and receiver operating characteristic curve analysis.
Results: In healthy individuals, CET positively correlated with CCT (r = 0.5, P < 0.001), the CET-to-CCT ratio being 0.100 ± 0.006. The CET-to-CCT ratio increased to 0.111 ± 0.009 (P < 0.001) and to 0.132 ± 0.021 (P < 0.001) at 1 day and 1 month postoperatively, respectively. The area under the curve for the CET-to-CCT ratio as a diagnostic criterion for previously performed myopic LASIK was 0.97 (sensitivity 93.5% and specificity 91.6%).
Conclusions: In healthy individuals, the corneal epithelium contributes a mean of 10.0% of corneal thickness. The CET-to-CCT ratio has a highly predictive value for indication of previously performed myopic LASIK. It seems that clinical application of epithelial thickness measurement can be improved by adjusting CET for CCT.