AimsTo investigate the differences between 0.2 and 0.15% brimonidine tartrate eye drops for anti-mydriatic effects and the optical quality under different light conditions.MethodsThis prospective study involved 80 consecutive high myopia patients undergoing implantation of a V4c ICL. The patients were randomly instilled with brimonidine 0.2 and 0.15% 2 weeks postoperatively. Visual quality, pupil center, pupil size, and refraction under different light conditions were measured before and 0.5 h after brimonidine administration. A symptom questionnaire was also evaluated.ResultsThere was no statistical difference in the static and dynamic pupil diameters and velocity after LS between the two groups (p> 0.05). The 0.2% group had significant changes in pupil center before and after treatment, while there was no obvious movement of the 0.15% group under all illumination condition (p> 0.05). The OSI after treatment of the 0.15% group was lower than that of 0.2% group (p= 0.012). The PVA9% and PVA100% of the 0.15% group was higher than that of 0.2% group in the dark (p= 0.009,p= 0.012). The HOA RMS of the 0.15% group was lower than that of 0.2% group (p= 0.016). The QIRC score in the 0.15% group was significantly higher than that in the 0.2% group (p= 0.043).Conclusion0.15 and 0.2% brimonidine tartrate eye drops had similar anti-mydriatic ability, while 0.15% group had better visual quality than 0.2% concentration, and hardly introduced pupil shift. 0.15% brimonidine tartrate eye drops may be more suitable for patients with nocturnal glare symptoms in the early postoperative period after ICL implantation.