Comparison of corneal flap striae and displacement after LASIK with microkeratome and femtosecond laser

Abstract

Objective To compare the early corneal flap striae and displacement between mechanical microkeratome and femtosecond laser for laser in-situ keratomileusis (LASIK). Methods The data of 5 792 cases with LASIK from Jan. 2016 to Jan. 2017 were analyzed retrospectively. All cases were randomly divided into two groups: group A received flap made by femtosecond laser in 3 358 cases and group B received flap made by mechanical microkeratome in 2 434 cases. Patients with flap striae and displacement above grade Ⅱ without obvious trauma history in the early postoperative periods were selected as research objects, the incidence rate and causes were compared between the two groups. Results The corneal flap striae and displacement occurred in 15 eyes (0.45 %) in group A and 22 eyes (0.90 %) in group B. The difference was statistically significant (χ2=4.647, P=0.031). The spherical equivalent of patients with corneal flap striae and displacement before surgery was (-7.71±1.38)D in group A and (-5.56±1.90)D in group B (t=-3.99, P=0.0003). The mean corneal flap thickness of patients with corneal flap striae and displacement was (84.29±5.78)μm in group A and (93.96±7.47)μm in group B. The difference of corneal flap thickness in two groups were not statistically significant between the displacement cases and the normal cases (t=0.34, P=0.73; t=-0.38, P=0.71). Conclusion The rate of corneal flap striae and displacement is related to the preoperative refraction and surgical method, but is not significant correlation with the thickness of the corneal flap. Femtosecond LASIK flaps represent significant improvement in predictability with implications for safety. Key words: Keratomileusis, laser in situ(LASIK); Flap creation, femtosecond laser-assisted; Flap creation, mechanical micro-keratome-assisted; Striae, corneal flap; Displacement, corneal flap