Blood viscosity in ocular hypertension.

Blood viscosity and its determinants were measured in 27 patients with primary open-angle glaucoma, 15 patients with ocular hypertension and 18 healthy control subjects matched for sex, blood pressure and smoking habits. The mean blood viscosity value was significantly higher in the glaucoma group than in the two other groups at all three shear rates studied; there was no difference in viscosity between the hypertension group and the control group. The mean hematocrit value was significantly lower in the hypertension group than in the two other groups. The results suggest that blood viscosity may contribute to nerve damage in patients with primary open-angle glaucoma. The low hematocrit observed in the patients with ocular hypertension may, by contributing to low viscosity, in some measure protect this group from optic nerve damage.