Visual and refractive outcomes of SMILE and FS-LASIK for high myopia

Abstract

Objective To compare the visual quality of small-incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) after correction for high myopia. Methods In this prospective non-randomized case-controlled study, patients were divided into a SMILE group (21 patients, 41 eyes) and a FS-LASIK group (19 patients, 38 eyes) based on the surgical method at the Department of Ophthalmology, West China Hospital. Routine ophthalmic examinations were performed.The patients were followed 6 months to monitor uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), refractive error, intraocular pressure, contrast sensitivity, corneal higher order aberrations, and scores for Quality of Life Impact of Refractive Correction Questionnaire (QIRC). Statistical analyses were performed using an independent samples t-test or Mann-Whitney U test. Results The safety index was 1.00±0.23 in the FS-LASIK group and 1.00±0.12 in the SMILE group. Log contrast sensitivity (LogCS) of 12.0 cycles per degree (cpd) was significantly higher in the SMILE group compared to the FS-LASIK group before surgery (t=2.137, P=0.035). The change in LogCS for 3.0 cpd at six months after surgery was significantly greater in the SMILE group compared to the FS-LASIK group (t=2.843, P=0.008), but other differences were statistically insignificant. The changes in total higher order aberrations, the third order coma, and the fourth order spherical aberration were greater in the FS-LASIK group than in the SMILE group during the same period (t=-7.587, P<0.001; t=-4.127, P<0.001; t=10.068, P<0.001; respectively). There was no significant difference in the amount of change in the QIRC scores between the two groups at 3 and 6 months postoperation. Conclusion Both SMILE and FS-LASIK can safely correct high myopia. Spatial frequency contrast sensitivity recovers better after SMILE surgery compared to FS-LASIK. Both SMILE and FS-LASIK increase corneal higher-order aberrations, but the FS-LASIK procedure induces more coma and spherical aberrations than SMILE. Key words: Small-incision lenticule extraction; Laser in situ keratomileusis; Femtosecond laser; High myopia; Visual quality