Predictive factors for efficacy and safety in refractive surgery for myopia.

PURPOSE:To evaluate the predictive factors for safety and efficacy in laser refractive surgery for myopia. SETTING:A singular refractive surgery center, at a University-affiliated tertiary medical center. DESIGN:Retrospective cohort study. METHODS:Study population-A total 8,775 eyes having laser refractive laser procedures for myopia (in4,623 patients). Observation procedures-Using a prospective database of refractive procedures performed over the span of 13 years, variables such as gender, age, type of surgery, date of surgery, pre-operative corneal thickness and Spherical Equivalent (SEQ) were evaluated. Main outcome measures-Proportion of patients with Safety index higher than 0.85 and Efficacy index higher than 0.80. RESULTS:91.9% and 86.0% of all evaluated eyes were above the safety and efficacy cut-off levels, respectively. Younger age was significantly correlated with safety and efficacy indices above the cut-off levels (p<0.001). Male gender was significantly correlated with efficacy above the cut-off level (p<0.001). Myopic eyes with lower SEQ were associated with both safety (p = 0.002) and efficacy (p<0.001) indices above the cut-offs. The surgical procedure was found to significantly affect the outcome only using univariate analysis: Safety was higher in Photorefractive Keratectomy (PRK), while Efficacy was higher in Laser Assisted In Situ Keratomileusis (LASIK) (p<0.001, respectively) but no difference was found using multivariate analysis. Safety index above the cut-off level increased over the years (p<0.001). CONCLUSIONS:Efficacy in refractive surgery for myopia is correlated with younger age, male gender and low myopia. Safety is correlated with younger age, low myopia and increases over the years. Multivariate analysis found no differences between PRK and LASIK regarding safety and efficacy