Effect of topical levobunolol on retinal and prelaminar circulation in normal subjects

Purpose. To evaluate the effect of levobunolol versus placebo on retinal and prelaminar blood flow in normal subjects in a double-masked placebo-controlled study. Methods. Our sample contained healthy subjects who first underwent an eye examination and a learning visual field with program 24-2 with the Humphrey Field Analyser. Subjects were then randomised to receive either levobunolol (0.5%) or placebo twice daily for one week in one randomly selected eye. Blood flow measurements were obtained pre- and post- treatment using the confocal Heidelberg Retina Flowmeter. In each session, we obtained three scans each centred on the optic nerve head at the retinal and prelaminar levels using the 10° scan angle. Five measurements each were then taken by two observers (with individual pre-and post-treatment images randomised) at the retinal level and at the prelaminar level in vessels not previously identified at the retinal level. Pre- and post-treatment visual fields and blood pressure measurements were also obtained. Results. To date, the results of 18 subjects (8 treatment and 10 placebo, mean age 31.5 yrs) have been analysed. There were no significant differences in pre- and post-treatment Mean Deviations, systemic or diastolic blood pressure in either group. Intraocular pressure decreased significantly from 17.13 to 14.88 mm Hg (P=0.005) in the treated group and from 15.90 to 14.40 mm Hg (P=0.081) in the control group. There were no pre- and post-treatment differences in any of the circulation parameters in either group with the notable exception of velocity at the retinal level in the treated group in which all 8 subjects showed a small (mean=3%) but significant (P=0.011) increase post-treatment. Conclusions. Topical levobunolol probably has little meaningful influence on retinal and prelaminar haemodynamics. The implications of the small increase in retinal blood velocity in the treated group is not clear.