Effect of eye laterality on correction of myopic astigmatism with small incision lenticule extraction (SMILE) using vector analysis.

Purpose: To compare the vector analysis, visual, and refractive outcomes after myopic astigmatic correction using SMILE between the right and left eyes.

Methods: This is a retrospective study including 41 right and 40 left eyes that underwent SMILE for correction of myopic astigmatism greater than 0.75 diopters (D) with a follow-up of at least 3 months. Vector analysis for astigmatic correction was done. Visual and refractive parameters were compared between both groups by measuring mean postoperative logMAR uncorrected distance visual acuity, mean postoperative spherical equivalent (SE), cylinder, and refractive predictability in terms of SE and cylindrical correction. Efficacy and safety of SMILE were also determined.

Results: No significant difference was found between vector outcomes except for angle of error (AE). The right eye group yielded a negative mean AE (- 2.71 ± 5.35), while the left eye group yielded a positive mean AE (0.23 ± 9.60). Correction index, magnitude of error and refractive predictability of cylindrical correction showed undercorrection of astigmatism in both groups. The right eye group showed lower predictability for higher cylindrical correction. Visual outcomes were similar for both eyes.

Conclusion: Rotational errors account for vectorial outcome differences between right and left eyes. Despite achieving good visual and refractive outcomes with low cylinder correction, the tendency to undercorrect between eyes due to this error may be more evident when treating higher amounts of astigmatism. More careful preoperative control for cyclotorsion is warranted for right eyes compared to left eyes.