Corneal changes after a single episode of selective laser trabeculoplasty for open angle glaucoma

Abstract

PURPOSE: To investigate the changes in central corneal thickness, endothelial cell count, and refraction after a single session of selective laser trabeculoplasty (SLT) for primary open angle glaucoma (POAG) and normal tension glaucoma (NTG). SETTING: Consecutive cases with open angle glaucoma were recruited from a glaucoma specialist clinic at a tertiary university hospital in Hong Kong. METHODS: In this prospective study, patients with POAG or NTG received a single session of SLT delivered in a single burst mode to 360° of the trabecular meshwork and energy was titrated from 0.8mJ until bubble formation was just visible. The following parameters were measured pre-SLT and 1 week and 1 month post-SLT: central corneal thickness via videokeratography, endothelial cell count via specular microscopy, and spherical equivalent via autorefraction. A one-way ANOVA with Tukey's Multiple Comparison Test was performed for all time points in each parameter. Statistical significance was defined as p<0.05. RESULTS: In 53 eyes of 32 patients, there were 28 left eyes and 25 right eyes. The mean number of SLT shots was 140.6±37.1 with a mean energy of 1.0±0.07mJ. The mean endothelial cell count significantly decreased from 2468±369.6 at baseline to 2298±464.0 at 1 week (p=0.0006) and regained to 2387±445.6 at 1 month post-SLT; there was no significant difference between the baseline and 1 month endothelial cell count. For the central cornea thickness and spherical equivalent, there were no significant differences at the various time intervals pre and post-SLT. CONCLUSIONS: SLT may induce a transient reduction in specular microscopy measured endothelial cell count at 1 week post-SLT with a gradual regain to baseline levels, possibly accounted for by a reversible endothelial cell edema. It remains a safe treatment modality for open angle glaucoma without evidence of permanent corneal biometry changes post laser.