title: Higher optic nerve sheath diameters are associated with lower ocular blood flow velocities in glaucoma patients.
abstract: OBJECTIVE
  To investigate the relationship between optic nerve sheath diameter (ONSD) and retrobulbar blood flow velocities, as measured by color Doppler imaging (CDI) in glaucoma patients.
  
  
  METHODS
  We performed a prospective, randomized, observer-masked study involving a total of 197 subjects. Once enrolled, they were divided by three groups: healthy controls (n = 51), normal-tension glaucoma patients (NTG, n = 58), and primary, open-angle glaucoma patients (POAG, n = 88). All subjects underwent a general ophthalmological examination, an ultrasound-based assessment of the ONSD, and a hemodynamic study of the retrobulbar vascularization using CDI. Non-parametric tests, chi-square contingency tables, and the Deming correlations were used to explore differences and correlations between variables in the diagnostic groups.
  
  
  RESULTS
  ONSD was not different between experimental groups (p = 0.28). ONSD correlated positively with the pulsatility index of the ophthalmic artery in healthy individuals (p = 0.007), but not in glaucoma patients (NTG: p = 0.41; POAG: p = 0.22). In NTG patients, higher ONSD values were associated with lower end-diastolic and mean flow velocities in the short ciliary arteries (p = 0.005 in both correlations). No such correlation was found in healthy nor POAG groups (p range between 0.15 to 0.96). ONSD was not associated with any CDI-related variable of the central retinal artery in any cohort. Venous outflow velocities were not associated with ONSD in any of the three groups.
  
  
  CONCLUSIONS
  ONSD is negatively correlated with retrobulbar blood flow velocities in glaucoma patients, but not in healthy controls.
authors.affiliation: Department of Ophthalmology, University Hospitals Leuven, Campus St. Raphaël, Kapucijnenvoer 33, 3000, Leuven, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Willekens
authors.forename: Luís
authors.initials: L
authors.lastname: Abegão Pinto
authors.forename: Evelien
authors.initials: E
authors.lastname: Vandewalle
authors.forename: Carlos
authors.initials: C
authors.lastname: Marques-Neves
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Stalmans
mesh_terms: D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use; D001783:Blood Flow Velocity; D019842:Ciliary Arteries / Q000502:physiology*; D004311:Double-Blind Method; D005260:Female; D005902:Glaucoma, Open-Angle / Q000188:drug therapy / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D057066:Low Tension Glaucoma / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D009186:Myelin Sheath / Q000473:pathology*; D009880:Ophthalmic Artery / Q000502:physiology*; D009900:Optic Nerve / Q000473:pathology*; D011446:Prospective Studies; D012161:Retinal Artery / Q000502:physiology*; D014065:Tonometry, Ocular; D018615:Ultrasonography, Doppler, Color; D014792:Visual Acuity / Q000502:physiology
chemical_list: D000959:Antihypertensive Agents