The pathophysiological mechanism involved in normal-tension glaucoma is still not fully understood. Besides intraocular pressure, vascular and rheological factors have been described. In the present study, the prevalence of silent myocardial ischemia in patients of the same age with normal-tension glaucoma, primary open-angle glaucoma and cataract was compared. Our findings indicate that in all three groups ischemic episodes occurred more frequently than described in normal people. The most striking observation, however, was the fact that in normal-tension glaucoma the frequency was twice that of the other two groups.