Effects of topical timolol on corneal endothelial cell morphology in vivo.

To determine the effect of topical timolol on corneal endothelial cell morphology in a randomized, controlled, double-masked study of 40 healthy human eyes, we photographed the central corneal endothelium with a contact specular microscope before and after two weeks of treatment with placebo (20 eyes), with 0.5% timolol with 0.01% benzalkonium chloride (ten eyes), or with 0.5% timolol without benzalkonium chloride (ten eyes). From the specular photomicrographs, we analyzed five morphologic cell characteristics by means of electronic digitizer and microcomputer--cell density, mean cell area, the coefficient of variation for cell area, mean cell perimeter and a new feature quantifying cell shape. Statistical analysis of the data showed that two weeks of exposure to topical timolol or its preservative had no significant effect on corneal endothelial cell morphology in young, healthy eyes in vivo.