Acute effect of topical β-adrenergic antagonists on normal perimacular hemodynamics

Purpose: β-adrenergic antagonists are the most commonly prescribed antiglaucoma medications. The nonselective β blocker timolol has been shown to either increase or to not affect retinal blood flow, despite the suggestion that the drug may cause vasoconstriction due to its blockade of β-2 receptors. Other β blockers with unique pharmacologies may produce different effects on blood flow. We studied the effects of betaxolol (β-1 selective antagonist), carteolol (nonselective β-antagonist with intrinsic sympathomimetic activity), and levobunolol (nonselective β antagonist with intrinsic sympathomimetic activity), and levobunolol (nonselective β antagonist with active polar metabolite) on perimacular hemodynamics. Method: On four separate occasions separated by at least 10 days, 16 normal subjects performed measurements of heart rate, blood pressure, IOP, and blue field entoptic simulation assessment of leukocyte velocity and density before and 2 h after instillation of one of the three drugs or an artificial tears placebo. Results: IOP was significantly reduced by all three drugs as compared to placebo (p < 0.05, Bonferroni-corrected two-tailed paired t-test). No significant differences were found in heart rate, blood pressure, and perimacular leukocyte velocity or density in any of the treatment conditions as compared to placebo. Conclusions: Betaxolol, carteolol, and levobunolol do not appear to significantly alter perimacular hemodynamics 2 h after administration. The absence of any acute change in hemodynamics despite the drop in IOP suggests normal autoregulation maintained constant blood flow.