Effect of brimonidine tartrate 0.10% ophthalmic solution on pupil diameter

Purpose: To evaluate the effect of brimonidine tartrate 0.10% ophthalmic solution on pupil diameter under light and dark luminance conditions. Setting: Ophthalmology Department, Tel Aviv Medical Center, Tel Aviv, Israel. Design: Case series. Methods: The pupil diameter was measured with a Colvard pupillometer in eyes of healthy volunteers under light (5.0 candelas [cd]/m ²) and dark (0.0 cd/m²) luminance conditions before brimonidine 0.10% instillation and after 30 minutes, 3 hours, and 6 hours. Results: The mean age of the 26 volunteers (52 eyes) was 34.73 years (range 19 to 60 years). Under light conditions, the mean pupil diameter was 4.98 mm ± 0.83 (SD) before instillation of brimonidine 0.10% and 4.64 ± 0.82 mm after instillation. The difference was not statistically significant, with 13.4% of eyes having a clinically significant reduction (>1.0 mm) in pupil diameter after 6 hours. Under dark conditions, the mean pupil diameter was 6.76 ± 1.08 mm before instillation of brimonidine 0.10% and 5.30 ± 0.85 mm after instillation; the difference was statistically significant (P<.001). There was a clinically significant reduction in pupil diameter after 6 hours in 90.4% of eyes. The antimydriatic effect under dark luminance conditions was more pronounced in eyes with light irides. Conclusions: Brimonidine 0.10% ophthalmic solution had an antimydriatic effect under dark luminance conditions and had a negligible effect on pupil diameter under light luminance conditions. The effect was similar to that reported in studies using higher concentrations of brimonidine.