Efficacy and predictability of laser in situ keratomileusis for low astigmatism of 0.75 diopter or less

PURPOSE: To examine the refractive and visual outcomes of wavefront-optimized laser in situ keratomileusis (LASIK) in myopic eyes with low astigmatism of 0.75 diopter (D) or less.

SETTING: University Medical Center Hamburg-Eppendorf, Germany, and Care Vision private clinics, Germany and Austria.

DESIGN: Retrospective cross-sectional data analysis.

METHODS: This study comprised consecutive myopic patients with a preoperative refractive cylinder of 0.75 D or less and a preoperative subjective sphere between -2.75 D and -11.50 D. Three subgroups were formed based on preoperative refractive cylinder magnitude (0.25 D, 0.50 D, and 0.75 D). Manifest refraction, uncorrected distance visual acuity (UDVA), and corrected distance visual acuity were assessed preoperatively and postoperatively. The astigmatic changes were determined using Alpins vector analysis.

RESULTS: This study enrolled 448 eyes of 448 patients (145 men, 303 women; mean age at surgery 37.8 years ± 9.4 [SD]). By 4 months (mean 116.8 ± 27.7 days) postoperatively, the mean UDVA was 0.10 ± 0.13 logMAR and the mean manifest refraction spherical equivalent (MRSE) -0.05 ± 0.68 D. There was no statistically significant difference in efficacy or safety between the preoperative cylinder groups. Astigmatic overcorrection for a preoperative cylinder of 0.25 D and 0.50 D was suggested by the correction index, the magnitude of error, the index of success, and the flattening index.

CONCLUSIONS: Although the mean UDVA and mean MRSE obtained by the 4-month follow-up were appropriate, a preoperative cylinder of 0.50 D or less was significantly overcorrected. Accordingly, caution should be used when considering full astigmatic correction for manifest cylinder of 0.50 D or less.