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

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.

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.

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).

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