Corneal light backscatter measured by optical coherence tomography after LASIK.
PURPOSE: To objectively quantify corneal light backscatter after LASIK using optical coherence tomography (OCT). METHODS: Twenty-eight eyes of 14 patients (mean age: 39.9 +/- 8.6 years) underwent LASIK surgery. Corneal images were taken with a custom built anterior segment OCT at 1310 nm before and 1 day, 1 week, and 1 month after surgery. Backscattered light from the epithelium and 10 equally divided corneal stromal layers of the central cornea were analyzed using custom software. Light scattering of the interface area (defined as seven image pixels [46.2 microm] in depth centered by the peak corresponding to the interface between the corneal flap and bed) was also calculated and compared to the light backscatter at an equivalent depth of the respective preoperative cornea. RESULTS: There were significant differences of light backscatter in different layers (analysis of variance [ANOVA]: F(10, 130) = 44.89, P = .0001), but no significant differences between right and left eyes preoperatively (ANOVA: F(10, 130) = 1.16, P = .32). After surgery, there were significant differences in light backscatter profiles of the central cornea (repeated measures ANOVA: F(30, 810) = 7.70, P = .0001) with significant increases at approximately 140 to 190 microm in depth from the corneal front surface at 1 day (post hoc test: P = .004) and 1 week (post hoc test: P = .001) postoperatively, compared to the baseline. One month after surgery, light backscatter increased significantly in the epithelium (post hoc test: P = .0001) and decreased significantly (post hoc test: P = .0001) at approximately 100 to 140 microm in depth. Light backscatter results of these interface areas (repeated measures ANOVA: F(3, 81) = 21.29, P = .0001) showed significant increases at 1 day and 1 week postoperatively (post hoc tests: P = .0001) compared to baseline results and 1-month postoperative results. CONCLUSIONS: Objective and quantitative analysis of corneal light backscatter from OCT demonstrated increasing comeal light scattering at the interface and subsequent recovery.