Purpose: There is some indirect evidence for altered autoregulation in patients with glaucoma, but only a few studies have measured ocular blood flow directly during changes in ocular perfusion pressure. The present study was designed to compare pulsatile choroidal blood flow and optic nerve head (ONH) blood flow during moderate increases in intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG) and normal controls. Design: Two nonrandomized studies comparing blood flow responses in glaucoma patients and controls in an open design. Participants and Controls: Sixteen patients with POAG glaucoma and 16 healthy gender-matched and age-matched controls were included in the choroidal blood flow experiments. The ONH blood flow experiment was performed in 14 POAG patients and 14 healthy gender-matched and age-matched controls. Methods:In the first study, pulsatile choroidal blood flowwas assessed by laser interferometric measurement of fundus pulsation amplitude (FPA). In the second study, ONH blood flow was measured using laser Doppler flowmetry. In both cohorts, the IOP was increased stepwise by 10 and 20 mmHg using a suction cup. Main Outcome Measures: Fundus pulsation amplitude and ONH blood flow. Results: The baseline values of FPA and ONH blood flow were lower in glaucoma patients as compared with age-matched and gender-matched healthy controls. In patients with POAG, FPA decreased by -4.5± 5.8% and -11.3± 4.9% during elevation of IOP of 10 and 20 mmHg, respectively. These results were not different from the results in healthy controls, where FPA decreased by -5.1± 3.4% and -12.2± 4.9% at the 2 pressure levels (P=0.23 between groups). Optic nerve head blood flow showed no changes during the increase of IOP of 10 and 20 mmHg in either of the 2 groups (glaucoma patients, + 2.1± 14.7% and-0.8± 15.2% ; healthy controls, + 4.3± 12.0% and + 0.2± 14.2% ; P=0.83 between groups). Conclusions: The present study does not provide evidence for altered autoregulation in patients with POAG during a moderate increase in IOP. However, these results do not necessarily contradict the concept of vascular dysregulation in glaucoma. Purpose: There is some indirect evidence for altered autoregulation in patients with glaucoma, but only a few studies have measured ocular blood flow directly during changes in ocular perfusion pressure. The present study was designed to compare pulsatile choroidal blood flow and optic nerve head (ONH ): blood flow during moderate increases in intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG) and normal controls. Design: Two nonrandomized studies comparing blood flow responses in glaucoma patients and controls in an open design. Participants and Controls: Sixteen patients with POAG glaucoma and 16 healthy gender-matched and age-matched controls were included in the choroidal blood flow experiments. The ONH blood flow experiment was performed in 14 POAG patients and 14 healthy gender-matched and age-matched controls. Methods: In the first study, pulsatile choroidal blood flow was assessed by laser interferometric measurement of fundus pulsation amplitude (FPA). In the second study, ONH blood flow was measured using laser Doppler flowmetry. In both cohorts, the IOP was increased stepwise by 10 and 20 mmHg using a suction cup. Main Outcome Measures: Fundus pulsation amplitude and ONH blood flow. Results: The baseline values ​​of FPA and ONH blood flow were lower in glaucoma patients as compared with age-matched and gender-matched healthy controls. In patients with POAG, FPA decreased by -4.5 ± 5.8% and -11.3 ± 4.9% during elevation of IOP of 10 and 20 mmHg, respectively. These results were not from the results in healthy controls, where FPA decreased by -5.1 ± 3.4% and -12.2 ± 4.9% at the 2 pressure levels (P = 0.23 between groups). Optic nerve head blood flow showed no changes during the increase of IOP of 10 and 20 mmHg in either of the two groups (glaucoma patients, + 2.1 ± 14.7% and-0.8 ± 15.2%; healthy controls, + 4.3 ± 12.0% and + 0.2 ± 14.2% ; P = 0.83 between groups). Conclusions: The present study does not provide evidence for alter ed autorregulation in patients with POAG during a moderate increase in IOP. However, these results do not decided contradict the concept of vascular dysregulation in glaucoma.