PRéCIS:: Instillation of brimonidine or timolol slowed visual field deterioration in patients with open-angle glaucoma; both brimonidine and timolol might improve the mean deviation (MD) slopes. PURPOSE: The purpose of this study was to investigate and compare the effects of 0.1% brimonidine and 0.5% timolol on the progressing visual field defects in open-angle glaucoma. PATIENTS AND METHODS: We evaluated 1 eye each of 68 glaucoma patients who were treated with at least 1 prostaglandin analog. Their baseline MD slopes were < -0.5 dB/y based on at least 5 Humphrey field analyzer measurements within 3 years. Eligible eyes were randomly assigned to brimonidine or timolol treatment groups and treatments were administered without the wash-out period. Clinical examinations were performed every 4 months for 2 years. We designated the MD slope as the primary endpoint. RESULTS: Ultimately, 56 eyes (brimonidine:timolol=26:30) were included in the present study (mean age=65.2 y). Dropout rates of brimonidine and timolol treatment groups were 27.8% and 6.3%, respectively. There were no significant differences in baseline intraocular pressure or MD slopes between brimonidine and timolol groups (12.7 and 12.9 mm Hg, P=0.77, and -1.22 and -1.08 dB/y, P=0.43, respectively). Intraocular pressure decreased significantly in the brimonidine group at 4, 8, 12, and 16 months, and in the timolol group at 4 months, without significant differences between the drugs (P=0.20). MD slopes significantly improved in both groups (brimonidine: -0.38 dB/y, P<0.001; timolol: -0.52 dB/y, P=0.04). Furthermore, there was no significant difference between groups in the primary endpoint (P=0.59). CONCLUSION: Brimonidine and timolol treatments improved MD slopes in open-angle glaucoma.