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hanruo liu, Teng Ma, Wenyuan Shi, Diya Yang, Ningli Wang; Measurement and Associations of the Optic Nerve Subarachnoid Space in Normal Tension and Primary Open Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5825. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Low cerebrospinal fluid pressure (CSF-P) may be involved in the pathogenesis of glaucoma. We performed a prospective observational clinical study to measure the area of optic nerve subarachnoid space (ONSASA) in normal tension (NTG), primary open angle glaucoma (POAG) and controls，and examined its associations with relevant ocular and systemic parameters.
The study included 30 NTG patients, 32 POAG patients and 35 healthy controls. By using B-scan ultrasound, we measured the optic nerve diameter (OND), optic nerve sheath diameter (ONSD) and ONSASA in all groups. Central corneal thickness (CCT), 24h intraocular pressure (IOP)，refractive error, and axial length were measured in all groups, with additional central retinal nerve fiber layer (RNFL) thickness, and visual field defect measurements in glaucomatous patients. Only one eye per patient was selected. Shapiro–Wilk’s test and Levene’s test were used to exam the normal distribution of data and the homogeneity of the variance. Kruskal–Wallis was used to compare the different variables between the diagnostic groups. One-way ANOVA with post hoc least significant difference analysis was performed to assess all the examinations groups.
The ONSASA from 3 to 7mm behind the globe in NTG (5.15±1.8mm2, p<0.001) was significantly smaller than in the POAG (6.24±1.6mm2) or control groups (6.4±2.2mm2). The measurements in the POAG and control groups were not significantly different (p=0.13). Visual field damage and CCT were not correlated with ONSASA in either of the glaucoma groups (POAG, p=0.52 and 0.37; NTG, p=0.49 and 0.79 respectively). ONSAS didn’t correlated with refractive error, and axial length in any groups. However, ONSASA did correlate with mean IOP and highest recorded IOP in NTG patients (r=0.53, p< 0.001 and r=0.66, p< 0.001), while it did not in POAG patients and healthy controls (p=0.86, p=0.46 respectively).
The smaller ONSASA in POAG patients with normal pressure compared with high pressure suggests a lower orbital CSF-P in NTG patients.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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