Influence of Temperature and Humidity on Laser in situ Keratomileusis Outcomes

PURPOSE: The influence of ambient factors on the results of refractive surgery is not well-known. This study evaluated the influence of temperature and humidity on laser in situ keratomileusis (LASIK) outcomes. METHODS: Two hundred thirty-seven patients who underwent LASIK at the Clivan Instituto de Oftalmologia in Salvador--Bahia--Brazil, between May 1999 and March 2000, were evaluated. A total of 156 (65.8%) patients were female. Mean age was 30.3 +/- 7.6 years. Refractive errors: 197 patients (83.12%) had compound myopic astigmatism, 17 patients (7.17%) had myopia, 11 patients (4.64%) had compound hyperopic astigmatism, and 12 patients (5.07%) had other. Results at 15 and 60 days after LASIK were compared according to different levels of temperature and humidity in the operating room during the procedure. RESULTS: Patients whose spherical equivalent refraction varied between -0.50 to +0.50 D at 15 days after LASIK had surgery performed when the temperature was 25.1 +/- 1.4 degrees C and humidity was 45.1 +/- 4.2%; for the others, temperature was 24.7 +/- 1.5 degrees C (P = .12) and humidity was 43.0 +/- 4.0% (P = .002). The linear regression coefficient showed that lower temperature levels were associated with lower spherical equivalent refractions at 60 days after LASIK (r2 = .14; P = .03) but not at 15 days after LASIK (P = .98). The evaluation of humidity indicated an influence at 15 days after LASIK (r2 = .44; P = .04), as well as at 60 days (r2 = .45; P = .0002). CONCLUSION: Operating room environment may influence LASIK outcomes; humidity may be more significant than temperature.