To evaluate the variation of 24-hours blood pressure in patients with normal tension glaucoma (NTG) and primary open-angle glaucoma (POAG).

Thirty patients with NTG, 30 patients with POAG, and 30 normal controls were enrolled in this study. Each subjects underwent 24-hours ambulatory blood pressure monitoring. The variation of each parameter and difference among NTG, POAG, and control groups were compared.

The lowest diastolic blood pressure (DBP) and the lowest mean arterial blood pressure (MAP) were significantly lower in the NTG group(51.9±11.3 mmHg and 66.9±13.1 mmHg) than in the POAG group(60.0±11.4 mmHg and 77.8±16.8 mmHg, p=0.048 and 0.024) and the control group(60.1±10.5 mmHg and 77.4±13.3 mmHg, p=0.047 and 0.031) during nighttime. More patients showed a lowest MAP less than 60 mmHg in the NTG group(8 patients, 27%) than in the POAG group(2 patients, 7%) and the control group(2 subjects, 7%, p=0.038 each). In addition, a decrease of more than 15% in DBP was more frequent in NTG group(17 patients, 57%) than in the POAG group(9 patients, 30%) and the control group(9 subjects, 30%, p=0.037 each).

Nocturnal reduction in blood pressure may play an important role in the pathogenesis of NTG in some patients. Therefore, nighttime blood pressure should be considered as an important reference factor in diagnosis and treatment of NTG.