Risk factors for night vision complaints after LASIK for myopia.

PURPOSE To study the preoperative risk factors for night vision complaints (NVCs) after LASIK in a clinical setting. DESIGN Retrospective noncomparative case series. PARTICIPANTS Seven hundred ninety-five patients (1488 eyes) who underwent LASIK for myopia up to -9.75 diopters (D) (from January 1 to December 31, 1999). SETTING Private clinic. METHODS A complete preoperative examination was performed. Patients had bilateral LASIK surgery using the Nidek EC-5000 non-wavefront guided slit-scanning excimer laser and the Moria LSK One microkeratome. Patients were observed postoperatively for 12 months. MAIN OUTCOME MEASURES The reported NVCs for each eye were rated on a subjective scale based on functional visual comfort. Clinically important NVC odds ratios (ORs) were calculated. RESULTS Reports of NVCs decreased considerably from 25.6% at 1 month to 4.7% at 12 months postoperatively, at which time all patients reported similar NVCs in both eyes. Stratification of risk factors at 12 months postoperatively showed a 2.8-times increase in NVCs for initial myopia of >5 D, a 2.5-times increase for an optical zone of </=6.0 mm, and a 2.9-times increase for a postoperative spherical equivalent outside +/-0.5 D of emmetropia. The role of attempted spherical correction, age of the patient, and postoperative spherical equivalent had significant importance in logistic regression of the OR throughout the first postoperative year. In a stepwise logistic regression using 6- and 12-month data, attempted spherical correction and optical zone were the most predictive factors of NVCs (P<0.001). Pupil size at any month postoperatively was not statistically predictive of postoperative NVCs in any differential model involving it. CONCLUSIONS Attempted degree of spherical correction, age, optical zone, and postoperative spherical equivalent were major risk factors of NVCs throughout the first postoperative year, whereas pupil size was not. Future wavefront studies that characterize higher order aberrations might be helpful for understanding individual visual aberrations while predicting quality of vision.