Comparison of biomechanical effects of small incision lenticule extraction and laser-assisted subepithelial keratomileusis.

Abstract

To compare the corneal biomechanical properties after small incision lenticule extraction (SMILE) group and laser-assisted subepithelial keratomileusis (LASEK) group. The SMILE group comprised 39 patients (75 eyes) while it was 38 patients (76 eyes) in the LASEK group. Corneal hysteresis (CH) and the corneal resistance factor (CRF) parameters were determined using the Ocular Response Analyzer preoperatively and at 1 and 3months postoperatively. There were significant differences in the preoperative manifest refraction spherical equivalent (MRSE), central corneal thickness (CCT), the planned ablation depth (AD) or CRF values between the two groups, except for the CH value (p=0.07). The CH and CRF values at 1 and 3months postoperatively were significantly lower than the preoperative values in both groups (p<0.01). The postoperative CH values were significantly lower in the LASEK group than in the SMILE group at both follow-up visits after adjusting for age, sex, preoperative CCT, preoperative SE, planned AD and the use of both eyes in the same subject (p<0.01). However, no significant differences were observed in postoperative CRF between groups (p=0.22 at 1month and p=0.41 at 3months). No significant correlation was found between the planned AD and the changes in CH or CRF at any follow-up visit in the SMILE group. The preoperative magnitude of CH and CRF may be predictors of postoperative changes in CH and CRF in the both groups. CH and CRF decreased after SMILE and LASEK. However, the changes in the CH values were less after SMILE than after LASEK.