24 HOUR BLOOD-PRESSURE MONITORING IN NORMAL-TENSION GLAUCOMA

Background-The few investigations that used continuous 24 hour blood p ressure monitoring to investigate whether blood pressure in patients w ith normal tension glaucoma is lower than in normal subjects yielded c onflicting results. Therefore, a prospective controlled trial was carr ied out. Methods-Systemic blood pressure was recorded continuously ove r a 24 hour period in 20 patients with normal tension glaucoma (IOP le ss than or equal to 21 mm Hg). Eight of them showed a localised loss o f the neuroretinal rim area and, in addition, optic disc haemorrhages- that is, focal ischaemic signs. Twenty healthy patients without glauco ma, who were hospitalised for cataract or retinal surgery, served as c ontrols. Blood pressure was automatically measured every 20 minutes du ring the day and every 40 minutes at night. Results-Both groups showed a significant (physiological) blood pressure drop at night, which was significantly (p<0.001, ANOVA) more pronounced in the group with norm al tension glaucoma than in the control group. There was a weak trend towards lower blood pressure values in the normal tension glaucoma gro up. Minima, maxima, and mean values of the systolic, diastolic, and me an arterial pressures did not differ significantly between the group w ith normal tension glaucoma and the control group. The greatest differ ences occurred with nocturnal systolic and diurnal diastolic values. T here were no significant differences between the subgroup with focal l esions and the other patients with normal tension glaucoma. Conclusion s-Patients with normal tension glaucoma tend to have lower blood press ure values (p>0.05, ANOVA) than normals; this difference is probably m uch smaller than formerly assumed. Patients with normal tension glauco ma, however, have significantly greater nocturnal blood pressure drops (p<0.001, ANOVA) than normal controls. Nocturnal blood pressure drops (relative day-night differences) may play a more important role in th e pathogenesis of normal tension glaucoma than the absolute height of the blood pressure.