Abstract
To report on the optic canal cross-sectional area (OCA) in Caucasian patients with normal-tension glaucoma (NTG) compared with Caucasian control subjects without known optic nerve (ON) diseases. Retrospective analysis of computed tomographic images of the cranium and orbits in 56 NTG patients (30 females and 26 males; 99 of 112 eyes; mean age 67.7 ± 11.1 years). Fifty-six age- and gender-matched subjects (mean age: 68.0 ± 11.2 years) without known ON diseases served as controls. The OCA at the orbital opening was measured in square millimeters by using the tool "freehand." Statistical analysis was performed by using the independent two-tailed t-test. The mean orbital opening OCA in NTGs measured 14.5 ± 3.5 mm2 (right OCA: 14.4 ± 3.6 mm2, left OCA: 14.5 ± 3.4 mm2) and in controls measured 18.3 ± 2.6 mm2 (right OCA: 18.5 ± 2.7 mm2, left OCA: 18.1 ± 2.5 mm2). The difference between NTG and controls was statistically significant (p < 0.000 for the right OCA, p < 0.000 for the left OCA). This study demonstrates narrower OCAs in Caucasian NTG patients compared with Caucasian control subjects without known ON diseases. Narrower OCAs might contribute to a discontinuity of the cerebrospinal fluid flow between the intracranial and orbital subarachnoid space in NTG patients. This might have an influence onto the pathophysiology in NTG.
Highlights
Normal-tension glaucoma (NTG) is a multifactorial disease of the optic nerve (ON) consistent with primary open-angle glaucoma (POAG), despite a normal intraocular pressure (IOP) [1]
In all NTG patients, computed tomographic (CT) scan was combined with cisternography that was performed if visual field defects showed progression, despite a low IOP
The mean glaucomatous visual field defect (MD) at time of CT was 13.9 ± 7.1 dB on the right eye and 13.5 ± 7.3 dB on the left eye
Summary
Normal-tension glaucoma (NTG) is a multifactorial disease of the optic nerve (ON) consistent with primary open-angle glaucoma (POAG), despite a normal intraocular pressure (IOP) [1]. Several IOP-independent factors such as vascular dysregulation [2], oxidative stress [3], and Abbreviations: OCA, optic canal cross-sectional area; NTG, normal-tension glaucoma; ON, optic nerve; CT, computed tomographic; CSF, cerebrospinal fluid; SAS, subarachnoid space; POAG, primary open-angle glaucoma; IOP, intraocular pressure; MECs, meningothelial cells; OAG, open-angle glaucoma; MD, mean deviation; SAP, standard automated perimetry; OCT, optic coherence tomography; ROI, region of interest; IIH, idiopathic intracranial pressure; ONSD, optic nerve sheath diameter; ICP, intracranial pressure; MRI, magnetic resonance imaging. Smaller Optic Canals in Normal-Tension Glaucoma autoinflammatory processes [4] have been considered in the pathogenesis of NTG. Several clinical and experimental studies [7,8,9,10,11,12] demonstrated a discontinuity of CSF flow along the ON
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