Purpose: To study the effects of topical brimonidine tartrate 0.2%, an alpha(2)-agonist ocular hypotensive drug, on retinal capillary blood flow in patients with ocular hypertension.
Methods: The study was a double-masked, randomized, placebo-controlled trial set in a tertiary eye center. Ocular hypertensive patients with repeatable intraocular pressures greater than 21 mm Hg and normal visual fields and optic disks were consecutively recruited. After an eye examination, baseline retinal blood flow measurements were made with confocal scanning laser Doppler flowmetry in one study eye. Patients were then randomly assigned to receive either brimonidine or placebo (saline) twice daily for 8 weeks. Blood flow and intraocular pressure measurements were then repeated after 4 and 8 weeks.
Results: Seventeen patients were randomly assigned to receive brimonidine, and 14 received placebo. One patient in each group failed to complete the study. The mean group differences in baseline age and intraocular pressure were not statistically significant (59. 23 [+/-10.24] and 52.23 [+/-16.46] years, respectively, and 24.84 [+/-2.08] and 24.56 [+/-2.85] mm Hg, respectively). Brimonidine reduced intraocular pressure by 17.90% and 16.17% at 4 and 8 weeks, respectively, with a significant difference in treatment effect compared with the placebo group (P <.007). The group difference in treatment effect in any of the three hemodynamic parameters velocity, volume, and flow was within 8% and not significantly different at 4 or 8 weeks (P.360). Based on a type I error of 0.05, our study had a power greater than or equal to 75% to detect group differences in treatment effect of greater than or equal to 15% to 20%.
Conclusions: Brimonidine reduces intraocular pressure without altering retinal capillary blood flow in patients with ocular hypertension.