Spectral-Domain Optical Coherence Tomography Epithelial and Flap Thickness Mapping in Femtosecond Laser–Assisted In Situ Keratomileusis

• Published in: American journal of ophthalmology 2014-08, Vol.158 (2), p.293-301.e1
• Main Authors: Rocha, Karolinne Maia, Krueger, Ronald R
• Format: Article
• Language: English
• Subjects: Adult; Cornea - pathology; Cornea - surgery; Female; Follow-Up Studies; Humans; Keratomileusis, Laser In Situ - methods; Lasers; Male; Myopia - pathology; Myopia - physiopathology; Myopia - surgery; Ophthalmology; Prospective Studies; Refraction, Ocular; Reproducibility of Results; Software; Surgery; Surgical Flaps - pathology; Tomography, Optical Coherence - methods; Treatment Outcome; Variance analysis; Visual Acuity; Young Adult
• ISSN: 0002-9394; 1879-1891
• DOI: 10.1016/j.ajo.2014.04.012

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.