Finger blood flow was studied by means of laser Doppler flowmetry in 12 patients with low tension glaucoma (LTG), 12 patients with primary open-angle glaucoma (POAG) and 12 normal subjects. Baseline flow, flow after immersion of the hand in warm water (+40 degrees C), and flow after exposure of the hand in cold water (+4 degrees C) were measured. Statistically significant differences were not found in each flow between the three groups of the patients (p greater than 0.05). Vasospastic response to warm and cold water was observed in 25% of LTG patients, 17% of POAG patients, and 25% of normal subjects. There was no significant difference between LTG, POAG, and normal subjects in finger blood flow.