Longitudinal evaluation of cornea with swept-source optical coherence tomography and Scheimpflug imaging before and after lasik

Swept-source optical coherence tomography (OCT) is the latest advancement in anterior segment imaging. There are limited data regarding its performance after laser in situ keratomileusis (LASIK). We compared the reliability of swept-source OCT and Scheimpflug imaging for evaluation of corneal parameters in refractive surgery candidates with myopia or myopic astigmatism. Three consecutive measurements were obtained preoperatively and 1 year postoperatively using swept-source OCT and Scheimpflug imaging. The study parameters included central corneal thickness (CCT), thinnest corneal thickness (TCT), keratometry at steep (Ks) and flat (Kf) axes, mean keratometry (Km), and, anterior and posterior best fit spheres (Ant and Post BFS). The main outcome measures included reliability of measurements before and after LASIK was evaluated using intraclass correlation coefficient (ICC) and reproducibility coefficients (RC). Association between the mean value of corneal parameters with age, spherical equivalent (SEQ), and residual bed thickness (RBT) and association of variance heterogeneity of corneal parameters and these covariates were analyzed. Twenty-six right eyes of 26 participants (mean age, 32.7±6.9 yrs; mean SEQ, ±6.27±1.67 D) were included. Preoperatively, swept-source OCT demonstrated significantly higher ICC for Ks, CCT, TCT, and Post BFS (P≥0.016), compared with Scheimpflug imaging. Swept-source OCT demonstrated significantly smaller RC values for CCT, TCT, and Post BFS (P≥0.001). After LASIK, both devices had significant differences in measurements for all corneal parameters (P≥0.015). Swept-source OCT demonstrated a significantly higher ICC and smaller RC for all measurements, compared with Scheimpflug imaging (P≥0.001). Association of variance heterogeneity was only found in pre-LASIK Ant BFS and post-LASIK Post BFS for swept-source OCT, whereas significant association of variance heterogeneity was noted for all measurements except Ks and Km for Scheimpflug imaging. This study reported higher reliability of swept-source OCT for post-LASIK corneal measurements, as compared with Scheimpflug imaging. The reliability of corneal parameters measured with Scheimpflug imaging after LASIK was not consistent across different age, SEQ, and RBT measurements. These factors need to be considered during follow-up and evaluation of post-LASIK patients for further surgical procedures.