Effect of beta-blocker eyedrops on corneal epithelial barrier function

To investigate the long-term effect of a topically applied beta-blocker on human corneal epithelium, the corneal epithelial barrier function and the superficial cell area of the corneal epithelium were evaluated. Seventeen normal healthy volunteers (without medication), 7 cataract patients (treated with pyrenoxine eyedrops) and 7 glaucoma or ocular hypertension patients (treated with 0.5% timolol maleate) were assigned to this study. The eyedrops had been used on a daily basis for at least 3 months. In the evaluation of corneal epithelial barrier function, fluorescein uptake was measured using a slitlamp fluorophotometer after application of 3 microl of 0.5% fluorescein for 10 min. In the evaluation of the superficial cell area, the central corneal epithelium was measured by tandem scanning confocal microscopy (TSCM). The healthy control and timolol groups were compared. Corneal fluorescein uptake in the healthy control, pyrenoxine and timolol groups was 20.3 +/- 3.2, 21.5 +/- 4.0 and 76.2 +/- 30.0 ng/ml (mean +/- standard error), respectively. There was a significantly higher fluorescein uptake in the timolol group compared to the pyrenoxine group (p = 0.0088) and the healthy control group (p = 0.0055). TSCM showed no significant difference in the superficial cell areas of the corneal epithelium between the healthy control and timolol groups. beta-Blocker eyedrops decreased the corneal epithelial barrier function. Their application was not accompanied by any biomicroscopic change in the superficial cell area.