title: Intraocular pressure correlates with optic nerve sheath diameter in patients with normal tension glaucoma.
abstract: OBJECTIVE
  1. Identify differences in optic nerve sheath diameter (ONSD) as an indirect measure of intracranial pressure (ICP) in glaucoma patients and a healthy population. 2. Identify variables that may correlate with ONSD in primary open-angle glaucoma (POAG) and normal tension glaucoma (NTG) patients.
  
  
  METHODS
  Patients with NTG (n = 46) and POAG (n = 61), and healthy controls (n = 42) underwent B-scan ultrasound measurement of ONSD by an observer masked to the patient diagnosis. Intraocular pressure (IOP) was measured in all groups, with additional central corneal thickness (CCT) and visual field defect measurements in glaucomatous patients. Only one eye per patient was selected. Kruskal-Wallis or Mann-Whitney were used to compare the different variables between the diagnostic groups. Spearman correlations were used to explore relationships among these variables.
  
  
  RESULTS
  ONSD was not significantly different between healthy, NTG and POAG patients (6.09 ± 0.78, 6.03 ± 0.69, and 5.71 ± 0.83 respectively; p = 0.08). Visual field damage and CCT were not correlated with ONSD in either of the glaucoma groups (POAG, p = 0.31 and 0.44; NTG, p = 0.48 and 0.90 respectively). However, ONSD did correlate with IOP in NTG patients (r = 0.53, p < 0.001), while it did not in POAG patients and healthy controls (p = 0.86, p = 0.46 respectively). Patient's age did not relate to ONSD in any of the groups (p > 0.25 in all groups).
  
  
  CONCLUSIONS
  Indirect measurements of ICP by ultrasound assessment of the ONSD may provide further insights into the retrolaminar pressure component in glaucoma. The correlation of ONSD with IOP solely in NTG patients suggests that the translaminar pressure gradient may be of particular importance in this type of glaucoma.
authors.affiliation: Department of Ophthalmology, Centro Hospitalar de Lisboa Central, Alameda de Santo António dos Capuchos, Lisbon, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Abegão Pinto
authors.forename: Evelien
authors.initials: E
authors.lastname: Vandewalle
authors.forename: Anna
authors.initials: A
authors.lastname: Pronk
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Stalmans
mesh_terms: D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D007429:Intraocular Pressure / Q000502:physiology*; D057066:Low Tension Glaucoma / Q000175:diagnosis* / Q000503:physiopathology; D009900:Optic Nerve / Q000000981:diagnostic imaging / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis* / Q000503:physiopathology; D014065:Tonometry, Ocular; D014463:Ultrasonography; D014792:Visual Acuity / Q000502:physiology; D014794:Visual Fields
chemical_list: D000959:Antihypertensive Agents