Decentration of optical zone center and its impact on visual outcomes following SMILE

Abstract

Purpose: To evaluate decentration from pupil center and corneal vertex normal following femtosecond laser small incision lenticule extraction (SMILE) for the treatment of myopia and myopic astigmatism.

Methods: This study evaluated 101 eyes of 101 patients with a spherical equivalent (SE) of -5.30 ± 1.72 diopters (D). Decentration was measured in the pupil-centered group (PC group) by video capture images and in the vertex normal-centered group (VNC group) using the WaveLight Oculyzer II (Alcon). The PC and VNC groups were further divided into 4 subgroups (1 PC, 2 PC and 1 VNC, 2 VNC) based on the displacement of the lenticule center. Uncorrected and corrected distance visual acuities, manifest refraction, and wavefront errors were measured preoperatively, and at 1 day, 1 week, 1 month, and 3 and 6 months postoperatively.

Results: Regarding efficacy and safety, at 6 months postoperatively, 65, 71, 83, and 53% of eyes had unchanged corrected distance visual acuity in 1 PC, 1 VNC, 2 PC and 2 VNC groups, respectively. Also, 97, 98, 100, and 97% of treated eyes had a postoperative uncorrected distance visual acuity 20/20 or better in the subgroups, respectively. In the groups mentioned above, 96, 100, 100, and 95% of eyes, respectively, were within ±0.5 D of the targeted SE. In terms of total higher-order aberrations, the 1 PC group was significantly higher than the 1 VNC group (P = 0.04), whereas the 2 VNC group was significantly higher than the 2 PC group (P = 0.02).

Conclusions: Our results demonstrate that better refractive outcomes will be achieved when the lenticule center is closer to the corneal vertex normal.