Effects of glaucoma medications on corneal endothelium, keratocytes, and subbasal nerves among participants in the Ocular Hypertension Treatment Study

PURPOSE: To compare subbasal corneal nerve and keratocyte density and endothelial characteristics of ocular hypertensive patients treated with medications or observation. METHODS: Participants in the Ocular Hypertensive Treatment Study (OHTS) randomized at Mayo Clinic to medication or observation were evaluated with specular microscopy annually for 6 years. Confocal microscopy was performed 78 to 108 months after enrollment. Subbasal nerve density was calculated by manual tracing and digital image analysis. Keratocyte density was determined by manual counting methods. Data were compared using a t test and a rank sum test. RESULTS: After 6 years, corneal endothelial cell density, percent hexagonal cells, and coefficient of variation of cell area for the observation (n = 21) and medication groups (n = 26) were similar (2415 ± 300 vs. 2331 ± 239 cells/mm; 63% ± 11% vs. 65% ± 10%; and 0.32 ± 0.07 vs. 0.30 ± 0.06, respectively). Of 38 participants undergoing confocal examination, the medication group (n = 19) had fewer nerves (3.8 ± 2.1 vs. 5.9 ± 2.0 nerves/frame; P = 0.02) and a lower nerve density (5643 ± 2861 vs. 9314 ± 3743 μm/mm; P = 0.007) than the observation patients (n = 10). An additional 9 patients in the observation group, who began medication before confocal scanning, had intermediate nerve densities. Full-thickness keratocyte density was similar, with 22,257 ± 2419 and 23,430 ± 3285 cell/mm in the observation and medication groups, respectively. CONCLUSIONS: Chronic administration of glaucoma medications causes a decrease in the number and density of corneal subbasal nerve fiber bundles but does not affect keratocyte density or corneal endothelial characteristics.