Correlation of spectral-domain OCT epithelial and flap thickness mapping, preoperative refractive error and postoperative regression in myopic Femto-LASIK

Session Details

Session Title: Imaging

Session Date/Time: Tuesday 16/09/2014 | 08:00-10:30

Paper Time: 08:58

Venue: Capital Hall B

First Author: : K.Rocha USA

Co Author(s): :    R. Krueger   W. Dupps           

Abstract Details

Purpose:

To evaluate the role of epithelial thickness remodeling on Femtosecond Laser-Assisted in situ Keratomileusis (LASIK) flap architecture using a Spectral-domain optical coherence tomography (SD OCT), in correlation with the spherical equivalent refraction treated and postoperative myopic regression.

Setting:

Cleveland Clinic Foundation, Cole Eye Institute

Methods:

40 myopic eyes of 20 patients underwent femtosecond laser LASIK using the ALLEGRETTO WAVE® Eye-Q Excimer Laser with a spherical equivalent refraction ranging from -1 to -7.25 diopters (mean -3.25±1.9). Two femtosecond lasers for flap creation were randomized between eyes, using the IntraLASE FS60 (IL) in one eye and WaveLight FS200 (FS) in the contralateral eye. Anterior segment SD OCT using the Optovue RTVue-100 (6 mm Pachymetry+Cpwr scans) was used to evaluate the epithelial thickness profile, Femto-LASIK flap, corneal architecture and corneal power preoperatively and 1 week, 1 month, 3 and 9 months postoperatively. The average thickness of the central (2mm), superior and inferior zones (2-5mm) was calculated. Manifest and wavefront refractions were performed at 1 week, 1 month, 3 and 9 months postoperatively.

Results:

Statistically significant epithelial thickening was observed in both IL and FS laser groups centrally (p=0.033 and p=0.042) and inferiorly (p=0.007 and p=0.013) at 1 month postoperatively in comparison with preoperative measurements. At 3 and 9 months the epithelium was thicker centrally (p=0.042 and p= 0.043 in the IL group; p=0.035 and p=0.041 in the FS group), inferiorly (p=0.031 and p=0.035 in the IL group; p=0.023 and p=0.031 in the FS group) and superiorly (p=0.04 and p= 0.044 in the IL group; p=0.042 and p=0.045 in the FS group). 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 coefficient 0.485, p = 0.0021 at 1 month; 0.587, p = 0.00102 at 3 months and 0.576, p = 0.0011 at 9 months, respectively). Flap thickness mapping revealed thickening of the Femto-LASIK flaps in both the IL and FS laser groups (p=0.045 and p=0.057) at 1 month; (p=0.003 and p=0.012) 3 months; and 9 months (p=0.005 and p=0.010) compared to 1 week postoperative. The corneal power change reconstructed from the SD-OCT maps shows a statistically significant steepening at 3 and 9 months along with myopic shift.

Conclusions:

Significant epithelial and flap thickening along with mild myopic regression was observed up till 3 months after Femto-LASIK, with the magnitude of each being correlated to the spherical equivalent refractive correction. Epithelial remodeling may play a predictive role on early refractive instability after LASIK and refractive enhancements should not be considered before 3 months postoperatively.

Financial Interest:

NONE