Vector analysis of high (≥3 diopters) astigmatism correction using small-incision lenticule extraction and laser in situ keratomileusis

Abstract

To compare the astigmatic correction in high myopic astigmatism between small-incision lenticule extraction and laser insitu keratomileusis (LASIK) using vector analysis. Hong Kong Laser Eye Center, Hong Kong. Retrospective case series. Patients who had correction of myopic astigmatism of 3.0 diopters (D) or more and had either small-incision lenticule extraction or femtosecond laser-assisted LASIK were included. Only the left eye was included for analysis. Visual and refractive results were presented and compared between groups. The study comprised 105 patients (40 eyes in the small-incision lenticule extraction group and 65 eyes in the femtosecond laser-assisted LASIK group.) The mean preoperative manifest cylinder was -3.42 D±0.55 (SD) in the small-incision lenticule extraction group and -3.47±0.49 D in the LASIK group (P=.655). At 3months, there was no significant between-group difference in uncorrected distance visual acuity (P=.915) and manifest spherical equivalent (P=.145). Ninety percent and 95.4% of eyes were within ± 0.5 D of the attempted cylindrical correction for the small-incision lenticule extraction and LASIK group, respectively (P=.423). Vector analysis showed comparable target-induced astigmatism (P=.709), surgically induced astigmatism vector (P=.449), difference vector (P=.335), and magnitude of error (P=.413) between groups. The absolute angle of error was 1.88±2.25 degrees in the small-incision lenticule extraction group and 1.37±1.58 degrees in the LASIK group (P=.217). Small-incision lenticule extraction offered astigmatic correction comparable to LASIK in eyes with high myopic astigmatism.