Effect of brimonidine on visual indices in patients with acute optic neuritis: A single blind randomized clinical trial

Purpose: This study investigates brimonidine's potential effect on visual functions, particularly contrast sensitivity (CS), an indicator of retinal ganglion cell function. Methods: In this single-blind, randomized clinical trial, 60 patients (aged 23-56) with first-episode acute optic neuritis within seven days of symptom onset were randomly assigned to brimonidine or control groups. The intervention group received brimonidine three times daily for three months, while the control group received synthetic tears with the same dosage and frequency. Primary outcomes were changes in CS, visual acuity (VA), and color vision at one and three months post-treatment. Repeated measures ANOVA was used to assess statistically significant and partial eta squared (eta 2) values, mean differences, and clinically significance important were reported. Results: All participants completed the study without complications. VA improved significantly in both groups by follow-up end (p < 0.001), with significant improvement from first to third month only in the brimonidine group (p < 0.001). The mean VA difference between groups was not statistically and clinically significant. CS showed statistically significant improvement within both groups (p < 0.001) and between groups (p < 0.001), with a large effect size (partial eta 2 = 0.28). The mean CS difference between groups (14.5) was clinically considerable. No significant changes in color vision were observed between groups (p = 0.96). Conclusion: Brimonidine significantly improved contrast sensitivity compared to placebo and was well-tolerated. Its neuroprotective effects suggest it may be beneficial in treating optic neuritis and preserving retinal ganglion cell function. Trial registration: Prospectively registered at Iranian Clinical Trial Registration; Registration date 3 December 2022; Registration number: IRCT20221127056631N1