Backscattered light from the cornea before and after laser-assisted subepithelial keratectomy for myopia

Abstract

To study corneal backscatter changes after laser-assisted subepithelial keratectomy (LASEK) and to search for correlations between the changes in forward and backward corneal light scatter. Antwerp University Hospital, Edegem, Belgium. Prospective interventional case series. Corneal backscatter was determined with a commercial Scheimpflug device and purpose-written image-analysis software. The mean backscatter profile and gray value distributions of the images for a 1.0 mm zone around the corneal apex were obtained preoperatively and 6 months after LASEK for myopia. This was compared with forward light scatter (or straylight) using measurements obtained with the compensation comparison method. The study enrolled 80 eyes (40 patients; mean age 34.2 years ± 10.4 [SD]). Very strong correlations were found between the backscatter profiles of right eyes and left eyes preoperatively. Hence, only right eyes were used for further calculations. The epithelial-Bowman peak of the backscatter profile decreased significantly after LASEK (mean decrease -2.2 ± 4.7 grayscale units) (P=.002, paired t test), which corresponded to the ablation of Bowman layer. Significant changes in the gray-value distribution were observed postoperatively, corresponding to the decreases in the epithelium-Bowman peak. Forward light scatter decreased significantly after LASEK (mean decrease -0.10 ± 0.13) (P<.001); however, no significant correlation with corneal backscatter was observed. The anterior part of the corneal backscatter profile decreased significantly after LASEK. A significant reduction in forward light scatter was also seen, although it was not correlated to backward light scatter.