Comparative Vector Analysis of Astigmatic Changes After Small-incision Lenticule Extraction versus Femtosecond Laser In -situ Keratomileusis
Abstract Purpose To compare thevisual outcomes of small-incision lenticule extraction (SMILE) versus femtosecond laser in-situ keratomileusis (FS-LASIK) in eyes with myopia and high astigmatism. Methods This retrospective study was conducted at a tertiary eye hospital between January 2021 and December 2022. Data were collected from individuals with myopia up to - 10.00 diopters (D) and cylinder ≥ 2.50 D who underwent SMILE (VisuMax 500) or FS-LASIK (MEL 90) and completed a 3-month postoperative follow-up. Results A total of 170 eyes of 123 patients were included: 83 eyes (60 patients) underwent SMILE, and 87 eyes (63 patients) underwent FS-LASIK. The preoperative cylindrical refractive error was - 3.01 ± 0.61 D in the SMILE group and - 3.09 ± 0.66 D in the FS-LASIK group. At 3 months, there was no statistically significant difference in uncorrected visual acuity (UCVA) or manifest refraction spherical equivalent (SEQ) between the two groups (P = 0.26 and P = 0.88, respectively). In the SMILE group, 90.4% of eyes achieved an uncorrected distance visual acuity (UDVA) of 20/20 or better compared to 98.77% with a preoperative corrected distance visual acuity (CDVA) of 20/20 or better. In the FS-LASIK group, 80.46% of eyes achieved a UDVA of 20/20 or better compared to 94.25% with a preoperative CDVA of 20/20 or better. Moreover, 95.1% of eyes in the SMILE group and 94.3% in the FS-LASIK group were within ± 0.50 D. Vector analysis showed comparable results between the two groups in terms of target-induced astigmatism (P = 0.559), difference vector (P = 0.155), index of success (P = 0.091), and angle of error (P = 0.89). The surgically induced astigmatism and correction index were significantly lower in the SMILE group (P < 0.01), whereas the absolute magnitude of error was higher in the SMILE group (P = 0.02). Conclusion SMILE and FS-LASIK have comparable efficacy, predictability, and safety in correcting myopia associated with high astigmatism ( ≥ 2.50 D).