Aims To define parameters of autonomic nervous system activity in patients with normal tension glaucoma (NTG).

Methods Ambulatory 24-h ECG (Lifecard CF) and 24-h blood pressure (BP) monitoring (SpaceLab 90207-30) were carried out in 54 patients with NTG (44 women, mean age 59.7) and 43 matched control subjects (34 women, mean age 57.0). Heart rate variability time and frequency domain parameters (low frequency (LF), high frequency (HF) and LF/HF ratio), BP variability (BPV), diurnal and nocturnal BP variables were compared between study groups.

Results Patients with NTG demonstrated higher LF, LF/HF and lower HF values than control subjects for the 24-h, daytime and night-time periods. The mean 24-h, daytime and night-time LF/HF ratios were statistically higher in patients with glaucoma as compared to control subjects ((3.2±1.5 vs 2.2±0.8, p=0.0009), (3.5±1.7 vs 2.7±1.0, p=0.0173) and (2.6±1.7 vs 1.4±0.6, p=0.0001), respectively). There were no statistical differences in the mean BP during the whole day, daytime and night-time, and in BPV (10.4±1.9 vs 10.5±2.1, p=0.790) between study groups. No difference was also found in the percentage decrease in night-time mean BP (12.3% vs 13.6%, p=0.720). ‘Dippers’, ‘non-dippers’ and ‘overdippers’ with NTG showed significantly higher LF/HF ratio as compared to the same subgroups of control subjects.

Conclusions The sympathovagal balance of autonomic nervous system in patients with NTG shifted towards sympathetic activity however with no change of 24-h pattern of BPV as compared to controls.