Randomized, contralateral eye study to evaluate the effect of standard and inverted side‐cut angle on corneal biomechanical properties during femtosecond laser‐assisted in situ keratomileusis

Abstract

To evaluate the effect of side-cut angle profile on corneal biomechanical properties after femtosecond laser in situ keratomileusis (FS-LASIK). Ninety-six myopic eyes of 48 patients underwent FS-LASIK. One eye of each patient was randomized to flap creation with a side-cut angle of 115°. The fellow eye flap side-cut angle was adjusted to 70°. Mean absolute error of flap diameter and mean change in Goldmann-correlated intra-ocular pressure (IOPg), corneal-compensated IOP (IOPcc), corneal hysteresis (CH), corneal resistance factor (CRF), p1 area, p2 area, p1 area 1 and p2 area 1 were compared between both groups. Overall, the mean IOPg and CRF showed significant reduction at the end of 1 and 3months, as well as between 1 and 3months postoperatively (p≤0.03). The mean IOPcc and CH showed significant reduction (p<0.001) at the end of 3months postoperatively. The parameters p1 area, p2 area, p1 area 1 and p2 area 1 changed significantly at the end of 1 and 3months postoperatively (p<0.001). There was no significant difference between both groups with regards to the mean change of IOPg, IOPcc, CH, CRF, p1 area, and p1 area 1. In 115° group, the mean absolute error in flap diameter was greater compared with 70° group (p=0.014). The stability of IOP and corneal biomechanical properties were not enhanced in FS-LASIK flaps with an inverted side-cut angle. The size of corneal flap created with 70° side-cut angle was more accurate compared with 115° side-cut angle.