Comparison of modulation transfer function between the eyes after small-incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis

Objective

To investigate and compare the changes of modulation transfer function (MTF) after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK).

Methods

A cohort study was conducted.One hundred and two myopic patients (102 eyes) who underwent SMILE and FS-LASIK in Tianjin Eye Hospital from December 2015 to June 2016 were enrolled and divided into SMILE group with 53 eyes and FS-LASIK group with 49 eyes according to different surgical methods.The ocular aberrations and corneal morphology of all patients were measured by the Hartman-Shack wave-front analyzer and Pentacam topography before surgery and 1, 3 and 6 months postoperatively.MTF of optic system was calculated and analyzed.The changes of MTF values were compared between the two groups at different time points under different spatial frequencies, after removal of low-order aberrations at postoperative 6 months, and after removal of vertical coma aberration, horizontal coma aberration and spherical aberration in the SMILE group at postoperative 6 months.The study protocol complied with the Declaration of Helsinki and was approved by an Ethics Committee of Tianjin Eye Hospital (No.TJYYLL-2014-17). Written informed consent was obtained from each patient before surgery.

Results

Compared with the preoperative MTF, there were significant increases in postoperative 1-, 3- and 6-month MTF at all spatial frequencies in the SMILE group and FS-LASIK group (all at P<0.05). MTF values at all spatial frequencies in the SMILE group were significantly higher than those in the FS-LASIK group at 1, 3, and 6 months after surgery (all at P<0.05), except at 55 c/d and 60 c/d at 6 months postoperatively.The postoperative 6-month MTF values at all spatial frequencies without low-order aberration were higher in the SMILE group than those in the FS-LASIK group, showing significant differences between the two groups (all at P<0.05). In the SMILE group, the postoperative 6-month MTF values at 1 c/d spatial frequency without the horizontal coma aberration and spherical aberration were significantly higher than the preoperative MTF values (both at P<0.01); the postoperative 6-month MTF values at 1 c/d and 3 c/d spatial frequency without vertical coma aberration were significantly higher than the preoperative MTF values (both at P<0.05), and there were no statistically significant differences between the postoperative 6-month MTF values at the other spatial frequencies with and without single high-order aberrations (all at P>0.05).

Conclusions

Optic quality has been obviously improved after SMILE and FS-LASIK, and the SMILE is superior to FS-LASIK in the MTF value.

Modulation transfer function; Small-incision lenticule extraction; Femtosecond laser-assisted laser in situ keratomileusis; Optic quality