PURPOSE: To investigate the effects of topical beta-blocker eyedrops on nocturnal arterial hypotension and heart rate and on visual field deterioration. METHODS: We prospectively investigated 275 white patients, 161 with glaucomatous optic neuropathy and 114 with nonarteritic anterior ischemic optic neuropathy, by 24-hour ambulatory blood pressure monitoring and diurnal curve of intraocular pressure, in addition to detailed ophthalmic evaluation. Of the patients with glaucomatous optic neuropathy, 131 had normal-tension glaucoma and 30 had primary open-angle glaucoma. Of the 275 patients, 114 were using topical beta-blocker eyedrops twice daily (76 with normal-tension glaucoma, 26 with primary open-angle glaucoma, and 12 with anterior ischemic optic neuropathy). RESULTS: Hourly average blood pressure data analyses showed overall a drop in blood pressure as well as heart rate during sleep, and a significantly greater drop in mean diastolic blood pressure ( P = .009) at night in normal-tension glaucoma than in anterior ischemic optic neuropathy. Also, patients using beta-blocker eyedrops experienced a significantly greater percentage drop in diastolic blood pressure at night ( P = .028), lower minimum nighttime diastolic blood pressure ( P = .072), and lower minimum nighttime heart rate ( P = .002) than did those not using them. In normal-tension glaucoma, eyes receiving beta-blocker eyedrops showed visual field progression significantly ( P = .0003) more often than those not receiving beta-blockers. CONCLUSIONS: The findings of our studies, as well as those of others, suggest that any factor that increases nocturnal arterial hypotension is a potential risk factor in vulnerable individuals with glaucomatous optic neuropathy or anterior ischemic optic neuropathy. The present study suggests that the use of beta-blocker eyedrops, by aggravating nocturnal arterial hypotension and reducing the heart rate, may be a potential risk factor in susceptible individuals.