Effect of laser in situ keratomileusis on retinal nerve fiber layer thickness measurements by scanning laser polarimetry

PURPOSE: To determine the effect of laser in situ keratomileusis (LASIK) on retinal nerve fiber layer measurements by scanning laser polarimetry in a large clinical trial. SETTING: Asan Medical Center, University of Ulsan, Department of Ophthalmology, Seoul, Korea. METHODS: Scanning laser polarimetry measurements were performed in 59 eyes of 59 consecutive patients who had LASIK. The mean retardation values of the whole measurement ellipse and of the superior, inferior, temporal, and nasal sectors of the ellipse before and after LASIK were compared statistically. RESULTS: The mean spherical equivalent refractive error was -6.10 diopters (D) +/- 2.34 (SD) (range -1.19 to -15.50 D) preoperatively and -0.31 +/- 0.52 D (range +0.68 to -2.13 D) postoperatively. The mean ablation depth was 94.0 +/- 30.49 microm (range 28.0 to 161.1 microm). The mean postoperative retardation values of all the sectors and of the superior, temporal, inferior, and nasal sectors showed reduced nerve fiber layer thickness (P =.000, P =.000, P =.011, P =.000, and P=.002, respectively). CONCLUSION: Laser in situ keratomileusis affected nerve fiber layer thickness measurements by scanning laser polarimetry. The change in nerve fiber layer thickness was probably due to modification of the corneal architecture. This effect of keratorefractive surgery should be considered when using scanning laser polarimetry as a diagnostic and follow-up tool for glaucoma.