PURPOSE: To evaluate the effect of laser-assisted in situ keratomileusis on retinal nerve fiber layer thickness measurements obtained with scanning laser polarimetry. METHODS: Thirteen consecutive eyes (13 patients) undergoing laser-assisted in situ keratomileusis were enrolled in this prospective study. Scanning laser polarimetry (NFA-GDx; Laser Diagnostic Technologies, Inc, San Diego, California) examination was performed 1 week before and 1 to 8 weeks after laser-assisted in situ keratomileusis surgery. Intraocular pressure was normal at all preoperative and postoperative examinations. Total mean, and superior, temporal, inferior, and nasal mean retinal nerve fiber layer thickness values before and after laser-assisted in situ keratomileusis were compared by Student paired t test. RESULTS: Mean ± SD patient age was 34.6 ± 10.9 years (range, 20 to 56 years). Mean ± SD preoperative spherical equivalent refractive error was -6.6 ± 3.1 diopters (range, -3.25 to -13.25 diopters) and mean ± SD spherical equivalent refractive surgical correction was -6.2 ± 3.0 diopters (range, -2.9 to -12.25 diopters). Total mean retinal nerve fiber layer and superior, inferior, temporal, and nasal mean retinal nerve fiber layer thicknesses were thinner after laser-assisted in situ keratomileusis (P = .01, for all comparisons, paired t test). CONCLUSIONS: Measurements of the retinal nerve fiber layer with scanning laser polarimetry depend on a corneal compensator inherent in the device. Keratorefractive surgery may affect scanning laser polarimetry measurements. Copyright (C) 2000 Elsevier Science Inc.