Comparison of Visual Quality after SMILE and FS-LASIK

Objective: To compare the visual quality between small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) in treating myopia and astigmatism. Methods: In this prospective non-randomized study, we selected 162 patients (324 eyes) with myopia and astigmatism who wanted refractive surgery in Changsha Aier Hospital from November, 2015 to February, 2016. The patients were allocated to either of two groups according to each person's request. The SMILE group had 78 patients (156 eyes) and the FS-LASIK group had 84 patients (168 eyes). All patients were followed up for 6 months. Uncorrected visual acuity (UCVA) and spherical equivalent (SE) were measured 1 day, 1 month, and 6 months after surgery. Corneal higher-order aberrations (HOAs) and decentration were measured 3 months after surgery. A vision quality questionnaire, based on a simplified version of Quality of Vision (QoV) Questionnaire to assess negative symptoms, was administered at 1 month and 6 months after surgery. Repeated measures ANOVA, ANOVA, chi-square test, and the rank-sum test were used to analyze and compare the data for the two groups. Results: One day after surgery, UCVA in the FS-LASIK group was better than in the SMILE group (t=4.555, P<0.001), but there were no significant differences between the two groups in the later periods. The SE in the SMILE group at 1 day after surgery were higher than in the FS-LASIK group (t=-2.952, P=0.003), but at 1 month and 6 months after surgery, there was no significant difference between them. HOA, spherical, coma, and trefoil aberrations were significantly increased in both groups at 3 months after surgery compared with the preoperative values (P<0.05). SMILE induced more spherical and trefoil aberrations compared with FS-LASIK (t=5.633, P<0.001; t=2.586, P=0.010). The cutting decentration with SMILE (0.17 ± 0.09 mm) was similar to FS-LASIK (0.18 ± 0.10 mm) (t=0.594, P=0.553). For SMILE patients, the rates and degrees of haloes at 6 months had declined compared with 1 month (χ2=5.547, P=0.019; Z=-2.283, P=0.022). For FS-LASIK patients, there were no significant changes in postoperative negative visual symptoms between 1 month and 6 months after surgery. There were also no significant differences between the two groups at 1 and 6 months. Conclusions: Vision recovery was slower with SMILE, and it induced more spherical and trefoil aberrations than FS-LASIK. Cutting decentration and the occurrence of negative visual symptoms were similar in both procedures. Key words: Keywords: small incision lenticule extraction; femtosecond laser; laser in situ keratomileusis; aberration; visual quality