AIMS--This study describes an investigation of the relation between the change of intraocular circulatory dynamics and visual field defect between primary open angle glaucoma (POAG) and normal tension glaucoma (NTG). METHODS--The method was to determine the blood flow velocity of the ophthalmic artery using colour Doppler imaging and quantitative peak systolic flow velocity, mean envelope velocity, end diastolic velocity, and Pourcelot resistivity index (RI) were determined. The visual field was examined using program 30-2 of the Humphrey field analyser: the mean deviation (MD) and corrected pattern standard deviation (CPSD) were calculated as indices for visual field defects. There were 25 patients with POAG and 25 patients with NTG. RESULTS--There were no significant differences in all the four indices of the ophthalmic arterial flow and in both of visual field indices between patients with POAG and those with NTG. However, NTG patients alone showed a statistically significant correlation between RI and MD. CONCLUSION--The results suggest the vascular resistance of the ophthalmic artery may be associated with the development of visual field defect in NTG patients.