Quantitative and Morphological Corneal Endothelial Changes After Selective Laser Trabeculoplasty and Retinal Photocoagulation

Selective laser trabeculoplasty (SLT) and retinal photocoagulation (RP) are two common laser procedures often performed at a wavelength of 532 nm, and may affect the corneal endothelium. This study used corneal specular microscopy to determine the impact of these procedures on the corneal endothelium. DESIGN: Retrospective cohort study in a private practice. METHODS: There were 249 eyes from 136 consecutive patients who underwent SLT for open-angle glaucoma and 132 eyes from 74 patients who underwent RP included. Corneal specular microscopy was performed immediately before and after each procedure and at 1-month postprocedure. Microscopy data included quantitative measures, such as cell density and central corneal thickness, and morphological measures, including percentage of hexagonal cells and coefficient of variation in cell area. RESULTS: There was a small (just over 1%) reduction in corneal endothelial cell count from pre-SLT to post-SLT (P = 0.008), and a statistically significant recovery at 1 month (P = 0.04). Central corneal thickness also transiently increased from pre-SLT to post-SLT (P = 0.03). Although polymegathism was unchanged, changes in pleomorphism were observed (P = 0.03). The only change in the RP group was an increase in polymegathism between pre-RP and post-RP (P = 0.001). CONCLUSIONS: SLT has measurable effects on both quantitative and morphological characteristics of the corneal endothelium, which seem to be transient. RP has fewer measurable effects, likely because, although the total laser energy is similar, it is delivered over a much longer time (3 ns versus 0.1 s). The changes observed in both procedures are minor and unlikely to be of clinical significance.