Comparison of corneal hysteresis and corneal resistance factor after small incision lenticule extraction and femtosecond laser-assisted LASIK: a prospective fellow eye study

Abstract

Purpose: To compare corneal hysteresis (CH) and corneal resistance factor (CRF) between eyes treated with small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (femto-LASIK).

Setting: Beyoğlu Eye Training and Research Hospital.

Design: Prospective comparative case series.

Methods: Sixty eyes from 30 patients with bilateral myopia or myopic astigmatism were studied. Inclusion criteria were spherical equivalent of subjective manifest refraction (SE) <10diopters (D) and a difference ≤0.50D between the SEs of both eyes. One eye of each patient was treated with SMILE, and the fellow eye underwent femto-LASIK. Randomization was performed using a sealed envelope system. The main outcome measures were CH and CRF measured preoperatively and postoperatively (1 and 6 months).

Results: Preoperative SE was similar in both groups (p=0.852). CH and CRF values were reduced postoperatively in both groups compared to their corresponding preoperative values (p<0.001). At the 6-month follow-up visit, the mean CH values in the SMILE and femto-LASIK groups were 8.95±1.47 and 9.02±1.27, respectively (p=0.852), and the mean CRF values were 7.77±1.37 and 8.07±1.26, respectively (p=0.380).

Conclusion: CH and CRF decreased after SMILE. There were no differences between SMILE and femto-LASIK treatments in postoperative CH or CRF values.

Keywords: Biomechanics; Corneal hysteresis; Corneal resistance factor; LASIK; SMILE; Small incision lenticule extraction.