Effects of brimonidine tartrate 0.1% ophthalmic solution on the pupil, refraction, and light reflex

This study aimed to assess changes in pupil size, uncorrected visual acuity, refraction, and the direct and consensual light reflexes after instillation of brimonidine 0.1% in healthy subjects. The investigation comprised 46 eyes of 23 healthy subjects with no eye diseases in whom brimonidine 0.1% was instilled in the right eye. Pupil size was measured quantitatively under photopic and scotopic conditions, uncorrected visual acuity, refraction, and direct and consensual light reflexes before and at 1, 6, and 24 h after instillation. We found No significant change was found in refraction or uncorrected visual acuity (P = 0.999 and P = 0.998, respectively). A significant reduction in pupil size was observed under scotopic conditions at 1 h and 6 h after instillation (P = 0.007 and P = 0.005, respectively). The rate of pupil contraction and constriction speed measured by light reflexes were significantly increased at 1 h and 6 h after instillation (P = 0.021 and P = 0.033, respectively). Brimonidine 0.1% induced a significant reduction in pupil size under scotopic conditions without a significant change in refraction or visual acuity due to suppression of the sympathetic nervous system.