Variation in the effectiveness of refractive surgery during the year: results from the Hamburg Weather Study.

Purpose: To examine the impact of seasonality on the refractive and visual outcomes of laser in situ keratomileusis (LASIK) in myopic eyes.

Setting: Department of Ophthalmology and Care Vision Refractive Centers, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Design: Retrospective cross-sectional data analysis.

Methods: Two subgroups were defined. The first comprised patients having surgery during meteorological winter and the second, patients having surgery during meteorological summer. The manifest refraction and uncorrected and corrected visual acuities were assessed preoperatively and postoperatively. Robust regression analysis was applied with the efficacy index, safety index, and postoperative SE as dependent variables.

Results: This study comprised 1052 eyes of 1052 consecutive myopic patients (419 men, 633 women; mean age at surgery 35.0 years ± 9.0 [SD]) with a mean preoperative refractive spherical equivalent (SE) of -3.88 ± 1.85 diopters (D). At the 1-month follow-up (mean 33.0 ± 5.0 days), the mean postoperative SE was -0.18 ± 0.44 D. The efficacy index was 0.023 higher in eyes with refractive surgery during summer than in eyes treated during winter (P=.032), indicating less efficacy during winter. The differences in the safety index and postoperative SE between summer and winter were not statistically significant. No eye had a change of more than 1 line on the logMAR scale (corrected distance visual acuity).

Conclusions: Although the difference in the efficacy index was statistically significant, the difference in the outcomes of LASIK was not clinically relevant, which shows the procedure's highly standardized reliability. Prospective longitudinal studies are warranted to address meteorotropic reactions by evaluating defined meteorological parameters.

Financial Disclosure(s): No author has a financial or proprietary interest in any material or method mentioned.