Evaluation of corneal flap symmetry in the optical center by anterior segment optical coherence tomography: mechanical versus femtolaser flaps

Objective The aim of this study was to evaluate corneal flap symmetry in the central 3 mm for subjects undergoing either laser in-situ keratomileusis or femtolaser in-situ keratomileusis for correction of myopia and/or astigmatism. Patients and methods This prospective study enrolled 160 eyes of 80 patients with mild to moderate myopia (<–6.00 D) as well as astigmatism less than −3.00 D. The corneal flaps of 80 eyes were created with the VisuMax femtosecond laser for intended thickness of 100 μm, and the other 80 eyes flaps were created by Moria M2 microkeratome (90 μm head) with intended thickness of 90 μm. The flap thickness was measured with a noncontact spectral-domain anterior segment optical coherence tomography system at three months postoperatively. The flap thicknesses were measured at five points (center and ±1.5 mm from the center) on each of the vertical and horizontal meridian (90° and 180°). Results The mean central thickness of the VisuMax and Moria M2 flaps was 102.06±5.37 and 130.25±12.61 μm, respectively (P<0.0001). In terms of mean flap thickness at each eccentricity, there were significant differences between the two groups, along the four measured eccentricities (P<0.0001). Conclusion The mean flap thickness measurements at each point showed more accurate outcomes in the femtolaser group. Moreover, slight vertical as well as horizontal asymmetry was found in the Moria group, although statistically insignificant.