Effect of one week of levobunolol HCl 0.5% on the human retinal circulation

To determine the effect of one week of topical treatment with levobunolol HCl 0.5% on the retinal circulation of normal subjects.

Fifteen healthy volunteers with no history of ocular disease were included in this study. In a double-masked, randomized, cross-over design, one eye of each subject was treated, for one week, with one drop of either levobunolol or placebo, administered twice daily. Following a washout period of at least three weeks, the same eye received the alternate treatment for one week. Before the beginning of therapy and then two hours after the last drop, vessel diameter (D), maximum erythrocyte velocity (Vmax), and volumetric blood flow rate (Q) were determined in one major retinal vein of the treated eye, using bidirectional laser Doppler velocimetry and monochromatic fundus photography. Statistical analysis was performed using two-tailed, paired Student's t-test, linear regression, and correlation analysis.

The average percentage change from baseline in intraocular pressure was statistically significant following levobunolol (-15% +/- 13% (+/-1 SD), P < .001), but not following placebo (-3% +/- 11%, P > .05). No significant changes in average D, Vmax, or Q were observed after levobunolol treatment (-1% +/- 4%, 5% +/- 11%, 4% +/- 15%, respectively) or placebo treatment (-1% +/- 4%, -2% +/- 9%, -5% +/- 10%, respectively). The average difference between the changes in Q from baseline after levobunolol and placebo treatments (9% +/- 17%) achieved a significance level of P = 0.06. Furthermore, following levobunolol treatment, Q was 7% +/- 14% higher than following placebo treatment (P = 0.05).

A comparison of the effects of placebo and levobunolol treatments suggests that levobunolol has a variable effect on the retinal circulation with a tendency to show an overall slight increase in flow.