Background: To evaluate the effect of brimonidine tartrate 0.15% ophthalmic solution on pupil size under scotopic condition and upper eyelid position.
Methods: This study comprised 72 eyes of 36 healthy subjects. A single drop of brimonidine tartrate 0.15% ophthalmic solution was instilled in the right eye and artificial tear was instilled in the left eye. Pupil size was measured using an infra-red pupillometer under scotopic condition before and at 30 min, 2, 4, 6, 8 and 10 h after instillation. Measurement of margin reflex distance 1 (MRD1) was performed using a millimetre ruler before and after at 10 min after instillation.
Results: The mean age of the subjects was 32.19 ± 11.43 years (range 10-52 years), 17 were female and 19 were male. Before brimonidine instillation, the mean pupil size was 6.09 ± 1.03 mm in the brimonidine eyes and 6.06 ± 1.04 mm in the control eyes. There was a significant decrease in mean pupil size at 30 min (4.45 ± 1.04), 2 h (4.49 ± 1.06), 4 h (4.59 ± 1.06), 6 h (4.89 ± 1.06) and 8 h (5.38 ± 1.02) after instillation compared to before in brimonidine eyes (p < 0.001 for all). There was a significant miosis continued for at least 6 h (5.95 ± 1.03) in control eyes (p < 0.001). There was no significant change in MRD1, before and after instillation both in brimonidine and control eyes.
Conclusions: Brimonidine tartrate 0.15% had a significant miosis under scotopic condition for at least 8 h after instillation and had a significant miosis on the untreated eye for at least 6 h.