title: Orbital cerebrospinal fluid space in glaucoma: the Beijing intracranial and intraocular pressure (iCOP) study.
abstract: OBJECTIVE
  Low cerebrospinal fluid pressure (CSF-P) may be involved in the pathogenesis of glaucoma. We measured the optic nerve subarachnoid space width (ONSASW) as a surrogate for orbital CSF-P in patients with primary open-angle glaucoma (POAG) with normal and high pressure and a control group.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  The study included 39 patients with POAG; 21 patients had normal pressure (intraocular pressure [IOP] 21 mmHg), and 18 patients had high pressure (IOP >21 mmHg); 21 subjects formed the control group.
  
  
  METHODS
  By using magnetic resonance imaging (MRI) with fat-suppressed fast recovery fast spin echo (FRFSE) T2-weighted sequence, we determined the ONSASW at 3, 9, and 15 mm posterior to the globe.
  
  
  METHODS
  The ONSASW and optic nerve diameter.
  
  
  RESULTS
  At all 3 measurement locations of 3, 9, and 15 mm, the ONSASW was significantly (P<0.001, P<0.001, and P = 0.003, respectively) narrower in the normal-pressure group (0.67±0.16, 0.55±0.09, and 0.51±0.12 mm, respectively) than in the high-pressure group (0.93±0.21, 0.70±0.12, and 0.62±0.11 mm, respectively) or the control group (0.87±0.15, 0.67±0.07, and 0.61±0.07 mm, respectively). The high-pressure and control groups did not vary significantly at 3, 9, and 15 mm (P = 0.31, P = 0.39, and P = 0.44, respectively). At all 3 measurement locations, ONSASW was narrower in the normal-pressure group compared with the high-pressure and control groups after adjustment for optic nerve diameter (P<0.01). Correspondingly, the width of the optic nerve subarachnoid space measured at 3, 9, and 15 mm behind the globe, respectively, was significantly (all P<0.05) associated with IOP after adjustment for optic nerve diameter and visual field defect.
  
  
  CONCLUSIONS
  The narrower orbital optic nerve subarachnoid space in patients with POAG with normal pressure compared with high pressure suggests a lower orbital CSF-P in patients with POAG with normal pressure.
authors: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, China. wningli@vip.163.com
authors: Ningli
authors: N
authors: Wang
authors: Xiaobin
authors: X
authors: Xie
authors: Diya
authors: D
authors: Yang
authors: Junfang
authors: J
authors: Xian
authors: Yong
authors: Y
authors: Li
authors: Ruojin
authors: R
authors: Ren
authors: Xiaoxia
authors: X
authors: Peng
authors: Jost B
authors: JB
authors: Jonas
authors: Robert N
authors: RN
authors: Weinreb
mesh_terms: D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology*; D006068:Gonioscopy; D006801:Humans; D019585:Intracranial Hypotension / Q000503:physiopathology*; D007427:Intracranial Pressure / Q000502:physiology*; D007429:Intraocular Pressure / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis / Q000503:physiopathology; D009900:Optic Nerve / Q000473:pathology*; D009915:Orbit; D011446:Prospective Studies; D013346:Subarachnoid Space / Q000473:pathology*; D014065:Tonometry, Ocular