Short-term effects of levobunolol on ocular pulsatile flow

In a randomized, double-masked, placebo-controlled study, we evaluated the effect of levobunolol 0.5%, a nonselective beta-blocker, on intraocular pressure, volume amplitude, and ocular pulsatile flow in healthy individuals and patients with glaucoma. Volume amplitude and ocular pulsatile flow were derived from measurements of pulse amplitude with a pneumatonometer. Two hours after instillation of levobunolol, intraocular pressure decreased from 26.0 ± 5.1 mm Hg to 17.8 ± 3.9 mm Hg (28.3%) (P < .001) in glaucomatous eyes and 20.2 ± 3.6 mm Hg to 14.5 ± 4.2 mm Hg (29.6%) (P < .001) in healthy eyes. Ocular pulsatile flow was increased after treatment with levobunolol from 482.1 ± 133.3 μl/minute to 548.5 ± 180.3 μl/minute (13.3%) (P < .006) in glaucomatous eyes and 457.6 ± 178.2 μl/minute to 528 ± 223.8 μl/minute (12.3%) (P > .05) in healthy eyes. There was no significant change in intraocular pressure, volume amplitude, or ocular pulsatile flow in placebo-treated eyes. The implication of these data for glaucoma therapy is not clear. Although we used an instrument that supposedly measures total pulsatile flow, it may be that optic nerve blood flow is dependent on total, both pulsatile and nonpulsatile, flow. Further, even though retinal blood flow is a small component of total ocular blood flow, it may be equally or more important than choroidal flow because of the necessity to maintain the perfusion of the retinal ganglion cells.