Ambulatory blood pressure monitoring in glaucoma: the nocturnal dip

Purpose: Hypoperfusion of the optic nerve head may be among the Significant factors relating to glaucoma damage. The physiologic nocturnal blood pressure 'dip' may be exaggerated in some patients and may compromise local vascular supply. Methods: Twenty-four-hour ambulatory blood pressure recording was performed on 38 patients with normal-tension glaucoma and on 46 with primary open-angle glaucoma. Eleven control subjects of similar age also were tested. The means of the systolic and diastolic blood pressures, mean arterial pressure, and pulse pressure for 24 hours, taken during the daytime (6 AM-10 PM) and night (10 PM-6 AM) periods were determined. The percentage nocturnal dip for each patient was calculated. A masked assessment of Humphrey visual fields for progression or stability was done on those 52 patients who had numerous fields plotted for more than 2 years. Results: The results of the control subjects confirmed that the authors' technique produces values similar to cardiologic studies from large healthy populations. The mean results from all the authors' patients with glaucoma were within the ranges reported for control subjects in the literature. The blood pressure parameters of the normal-tension glaucoma and primary open- angle glaucoma groups did not differ significantly. All nocturnal pressure parameters (except pulse pressure) were lower in the 37 patients with progressive field defects compared with the 15 patients whose pressure parameters were stable, whereas the systolic, diastolic, and mean arterial pressure dips were significantly larger (systolic dip, P = 0.001). Conclusion: The nocturnal reduction in blood pressure may be an additional risk factor in patients with glaucoma.