Spectral-domain optical coherence tomography epithelial and flap thickness mapping in femtosecond laser-assisted in situ keratomileusis.

Purpose To evaluate the change of epithelial and flap thickness after femtosecond laser–assisted in situ keratomileusis (LASIK) using spectral-domain optical coherence tomography (SD OCT) in correlation with the spherical equivalent refraction treated and clinical outcomes. Design Prospective, randomized, contralateral-eye study. Methods Forty myopic eyes underwent LASIK using an excimer laser with refraction ranging from −1.00 to −7.25 diopters (mean −3.25 ± 1.9). Flap creation was randomized between eyes, using the IntraLASE FS60 laser (IL) in 1 eye and WaveLight FS200 laser (FS) in the contralateral eye. SD OCT was used to evaluate the epithelial and flap thickness profiles and corneal power preoperatively and at 1 week and 1, 3, and 9 months postoperatively. Manifest and wavefront refractions were performed at each postoperative visit. Results Statistically significant epithelial thickening was observed in both IL and FS groups as early as 1 month postoperatively ( P  = .033 and P  = .042), but this stabilized between 3 ( P  = .042 and P  = .035) and 9 months ( P  = .043 and P  = .041). Femtosecond-LASIK flaps were thicker in the IL group in comparison to the FS group at 3 and 9 months postoperatively ( P  = .003 and P  = .005, respectively). There was a statistically significant correlation between the magnitude of preoperative myopic refraction and the central epithelial thickness at 1, 3, and 9 months (Pearson correlation coefficients 0.485, 0.587 and 0.576) ( P  = .0021, P  = .0010, and P  = .0011), respectively. SD OCT corneal power maps showed steepening at 3 and 9 months along with mild myopic shift. Conclusion Progressive epithelial and flap thickening with increased corneal power were observed after femtosecond laser-assisted in situ keratomileusis for myopia with consequent stabilization between 3 to 9 months postoperatively. The magnitude of epithelial and flap thickness remodeling correlated to the preoperative myopic refractive error.