Effect of brimonidine tartrate ophthalmic solution 0.2% on pupil size in normal eyes under different luminance conditions

Purpose: To evaluate the effect of brimonidine tartrate ophthalmic solution 0.2% (Alphagan (R)) on pupil size in normal eyes. Three luminance conditio ns were used to assess the potential use of brimonidine in postoperative re fractive patients who experience nighttime vision problems related to large pupil size. Setting: McDonald Eye Associates, Fayetteville, Arkansas, USA. Methods: Pupil size was measured in 16 eyes of 16 participants with the Col vard pupillometer under 3 luminance conditions. One drop of brimonidine 0.2 % was administered to each patient, Pupil size was then measured using the same technique 30 minutes and 4 and 6 hours after drop administration. Results: Under scotopic conditions, 100% or the pupils showed significant m iosis at 30 minutes (P <.05). The effect continued in all eyes for ii hours , At 6 hours, a miotic effect was still present in 81.3%. However, under ph otopic luminance, there was no significant effect on pupil size in ail 16 e yes (P >.05). The pupil size in 5 eyes (31.2%) was not affected at 30 minut es or 4 or 6 hours. At 6 hours, 15 eyes (93.8%) had returned to their prein stillation size. Conclusion: Brimonidine tartrate 0.2% had a significant effect in decreasin g pupil size under scotopic conditions, The results indicate that the drug can decrease night-vision difficulties such as halos, star bursts, glare, a nd monocular diplopia in postoperative refractive patients.