Neuroretinal rim area and ocular haemodynamic parameters in patients with normal-tension glaucoma with differing intracranial pressures

Purpose: To assess the differences in the neuroretinal rim area (NRA) and ocular haemodynamic parameters in patients with normal-tension glaucoma (NTG) with differing intracranial pressure (ICP) values. Methods: 40 patients (11 males) with NTG (age 61.1 (11.5)) were included in the prospective study. Intraocular pressure (IOP), non-invasive ICP, retrobulbar blood flow (RBF) and confocal laser scanning tomography for optic nerve disc (OND) structural parameters were assessed. Non-invasive ICP was measured using a novel two-depth Transcranial Doppler device. RBF was measured using colour Doppler imaging in the ophthalmic artery (OA). The patients were divided into two groups, ICP ≥ and <8.3 mm Hg, based on the statistical median of ICP. p Values <0.05 were considered statistically significant. Results: Patients with NTG had mean ICP 8.8 (2.5) mm Hg, IOP 13.6 (2.1) mm Hg, OND size 2.3 (0.6) mm², NRA 1.2 (0.4) mm². Lower ICP was correlated with decreased NRA (r=0.51, p=0.001). Patients with NTG having lower ICP (N=20) had significantly lower NRA 1.0 (0.3) mm², than patients with NTG having higher ICP (N=20) 1.3 (0.3) mm², p=0.002, although there were no significant differences in OND size (accordingly, 2.2 (0.5) and 2.3 (0.6) mm², p=0.55) and IOP (accordingly, 13.5 (2.4) and 13.7 (1.8) mm Hg, p=0.58). Patients with NTG having lower ICP had significantly lower OA blood flow velocities (peak systolic volume (PSV) 28.7 (8.0), end-diastolic volume (EDV) 6.9 (3.0) cm/s), compared with patients with NTG having higher ICP (PSV 35.5 (10.2), EDV 9.4 (4.1) cm/s), p<0.04. Conclusions: Patients with NTG having lower ICP have decreased neuroretinal rim area and OA blood flow parameters compared with patients having higher ICP. Further longitudinal studies are needed to analyse the involvement of ICP in NTG management.