The effect of long-term topical administration of commercial beta-blockers on the rat corneal endothelium.

To determine the effect of long-term topical application of commercial beta-blockers on the corneal endothelium, normal rats were randomly assigned to receive a drop of 0.5% timolol, 1% befunolol, or 2% carteolol four times daily for 8 months. Specular microscopy showed marked pleomorphism in the endothelium after three months of treatment with 1% befunolol. In contrast, the eyes treated with either 0.5% timolol or 2% carteolol demonstrated no significant change in endothelial morphology. Scanning and transmission electron microscopy at eight months after treatment revealed marked degeneration of the endothelium of the eyes treated with 1% befunolol. Similar endothelial changes were also noted in the 0.5% timolol-treated group, but to a significantly lesser extent. The eyes treated with 2% carteolol, however, showed only mild alteration of the endothelial ultrastructure. These results indicate that the corneal endothelium can be affected by long-term topical administration of commercial beta-blockers.