Comparison of Refractive Outcomes and Optical Zone Decentration After SMILE Between Patients With Symmetrical and Asymmetrical High Astigmatism.

PURPOSE: To compare the refractive outcomes and optical zone decentration between patients with symmetrical and asymmetrical high astigmatism after small incision lenticule extraction (SMILE).

METHODS: This was a prospective analysis of 89 patients (152 eyes) with myopia and astigmatism of more than 2.00 diopters (D) treated with the SMILE procedure. There were 69 eyes with asymmetrical topographies (asymmetrical astigmatism group) and 83 eyes with symmetrical topographies (symmetrical astigmatism group). Decentralization values were assessed using the tangential curvature difference map preoperatively and 6 months after surgery. Decentration, visual refractive outcomes, and induced changes in corneal wavefront aberrations were compared between the two groups 6 months postoperatively.

RESULTS: Both groups achieved favorable visual and refractive outcomes, with a mean postoperative cylinder of -0.22 ± 0.23 and -0.20 ± 0.21 D in the asymmetrical and symmetrical astigmatism groups, respectively. In addition, visual and refractive outcomes and induced changes in corneal aberrations were comparable between the asymmetrical and symmetrical astigmatism groups (all P > .05). However, the total and vertical decentration in the asymmetrical astigmatism group was greater than that in the symmetrical astigmatism group (all P < .05), whereas no significant differences were found in the values of horizontal decentration between the two groups ( P > .05). There was a weak positive correlation between induced total corneal higher order aberrations and total decentration ( r = 0.267, P = .026) in the asymmetrical astigmatism group but not in the symmetrical astigmatism group ( r = 0.210, P = .056).

CONCLUSIONS: An asymmetrical corneal surface might affect treatment centration after SMILE. Subclinical decentration may be associated with the induction of total higher order aberrations, but it did not affect high astigmatic correction or induced corneal aberrations. [ J Refract Surg . 2023;39(4):273-280.] .