ABSTRACT: This study evaluates the efficacy and tolerability (ie, occurrence and severity of hyperemia) of bimatoprost 0.01% in treatment-naïve patients with open-angle glaucoma (OAG) or ocular hypertension in the Korean clinical setting.In this multicenter, open-label, observational study, treatment-naïve patients with OAG, including patients with normal-tension glaucoma (NTG, defined as IOP ?21 mm Hg), or ocular hypertension received bimatoprost 0.01% once daily. Hyperemia was assessed at baseline and weeks 6 and 12, graded by a masked evaluator using a photonumeric scale (0, +0.5, +1, +2, +3), and grouped as (0 to +1) and (+2 to +3). Shifts between groupings were reported as no change, improved ([+2 to +3] to [0 to +1]), or worsened ([0 to +1] to [+2 to +3]). Other adverse events were monitored. Mean IOP changes from baseline at weeks 6 and 12 were reported. Supplemental analyses were conducted for IOPs >21 versus ?21 mm Hg.Of 295 treatment-naïve patients included in the intent-to-treat/safety population, 73 (24.7%) had baseline IOP >21 mm Hg (mean, 25.7 ± 5.0 mm Hg) and 222 (75.3%) had baseline IOP ?21 mm Hg (mean, 16.3 ± 3.0 mm Hg); 96.3% had hyperemia graded none (36.3%) to mild (17.3%). At week 12, hyperemia was graded none to mild in 83.7% (n = 220). Worsening occurred in 12.3% of patients by week 6 and 12.7% by week 12. Small improvements occurred in 0.8% and 0.5% of patients at weeks 6 and 12, respectively. Hyperemia scores were generally low and the majority of patients had no change in severity during the study. Mean IOP at weeks 6 and 12 was reduced to 16.4 ± 4.0 mm Hg (-34.5%; P < 0.0001) and 16.7 ± 3.9 mm Hg (-32.0%; P < 0.001) in the baseline-IOP >21 mm Hg group versus 13.3 ± 2.6 mm Hg (-17.8%; P < 0.001) and 13.7 ± 2.8 mm Hg (-15.9%; P < 0.001) in the baseline-IOP ?21 mm Hg group, respectively.In treatment-naïve patients, bimatoprost 0.01% induced low shifts in worsening of hyperemia and significant reductions in IOP, regardless of baseline IOP.NCT01594970.