title: The Optic Canal: A Bottleneck for Cerebrospinal Fluid Dynamics in Normal-Tension Glaucoma?
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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-tailedt-test.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Ophthalmology, Cantonal Hospital , Aarau, Aargau , Switzerland.
authors.forename: Achmed
authors.initials: A
authors.lastname: Pircher
authors.affiliation: Department of Ophthalmology, Cantonal Hospital, Aarau, Aargau, Switzerland; Department of Neuroradiology, Cantonal Hospital, Aarau, Aargau, Switzerland.
authors.forename: Margherita
authors.initials: M
authors.lastname: Montali
authors.affiliation: Department of Neuroradiology, Cantonal Hospital , Aarau, Aargau , Switzerland.
authors.forename: Jatta
authors.initials: J
authors.lastname: Berberat
authors.affiliation: Department of Neuroradiology, Cantonal Hospital , Aarau, Aargau , Switzerland.
authors.forename: Luca
authors.initials: L
authors.lastname: Remonda
authors.affiliation: Department of Ophthalmology, Cantonal Hospital , Aarau, Aargau , Switzerland.
authors.forename: Hanspeter E
authors.initials: HE
authors.lastname: Killer
keywords: cerebrospinal fluid; glaucoma; normal-tension glaucoma; optic canal; optic nerve