Recent findings indicate that low-tension glaucoma is associated with impaired ocular blood flow. In the present study we evaluated the blood-flow in the ophthalmic artery in regulated open-angle glaucoma. Using pulsed Doppler sonography (4 MHz), the blood-flow velocity in the ophthalmic artery of 183 eyes of 95 persons with open-angle glaucoma was examined (mean age, 66.6 +/- 14.5 years). The patients showed advanced glaucomatous optic-nerve atrophy (cup-to-disk ratio, 0.74 +/- 0.27) and regulated intraocular pressure (IOP: range, 8-25 mm Hg; mean, 16.4 +/- 3.9 mm Hg). The blood pressure (BP) was 140 +/- 22 (systolic) and 79 +/- 14 mm Hg (diastolic). The control group (84 eyes of 44 persons: mean age, 69.7 +/- 7.7 years; IOP range, 10-22 mm Hg; mean IOP, 15.2-2.6 mm Hg; BP, 143 +/- 20/81 +/- 9 mmHg was matched for age and circulatory risk factors. The vascular resistance index (RIO) was calculated by the equation RIO = (systolic blood velocity-diastolic blood velocity)/systolic blood velocity. We found that the blood velocity in the ophthalmic artery was significantly decreased in glaucomatous eyes in contrast to normal eyes: systolic peak velocity, 36.9 +/- 16.2 cm/s (normal, 40.2 +/- 10.9 cm/s; P < 0.001); diastolic peak velocity 9.9 +/- 4.4 cm/s (normal, 11.7 +/- 4.0 cm/s, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)