title: Oximetry in glaucoma: correlation of metabolic change with structural and functional damage.
abstract: OBJECTIVE
  To determine whether retinal vessel oxygen saturation in patients with glaucoma is associated with structural optic disc and retinal nerve fibre layer (RNFL) changes and visual field (VF) defects.
  
  
  METHODS
  Fifty-nine patients with confirmed glaucoma were recruited at University Hospitals Leuven. Retinal oxygen saturation in patients with glaucoma was measured with a noninvasive spectrophotometric retinal oximeter (Oxymap ehf, Reykjavik, Iceland). VF and Heidelberg retinal tomographies (HRTs) were performed on the same day. Statistical analysis was performed using Student's t-test and Pearson's or Spearman correlation coefficient.
  
  
  RESULTS
  The mean oxygen saturation in venules was higher in patients with severe VF defects compared to those patients with mild VF defects (69 ± 3% versus 65 ± 6% respectively; p = 0.0003; n = 59). Accordingly, the arteriovenous (AV) difference in oxygen saturation was lower in patients with worse VF compared to those with better VF (29 ± 3% versus 33 ± 6% respectively; p = 0.002). The oxygen saturation in venules correlated with the VF mean defects (r = -0.42; p = 0.001; n = 59) as well as with the structural HRT parameters rim area and RNFL thickness (r = -0.39; p = 0.008 and r = -0.26; p = 0.05 respectively; n = 53). The AV difference decreased significantly as the VF defect worsened (r = 0.38; p = 0.003), as the rim area diminished (r = 0.29; p = 0.03) and as the RNFL thickness decreased (r = 0.27; p = 0.05). No correlation was found between the oxygen saturation in retinal arterioles and either of these parameters.
  
  
  CONCLUSIONS
  Severe glaucomatous damage is associated with increased oxygen saturation in retinal venules and decreased AV difference in oxygen saturation. These data suggest that in eyes with severe glaucomatous damage, reduced retinal oxygen consumption is consistent with tissue loss.
authors: Laboratory of Ophthalmology, KULeuven, Leuven, BelgiumDepartment of Ophthalmology, University Hospitals Leuven, Leuven, BelgiumDepartment of Pharmacology and Neurosciences, Faculty of Medicine, Lisbon University, Lisbon, PortugalDepartment of Ophthalmology, Centro Hospitalar de Lisboa Central, Lisbon, PortugalDepartment of Ophthalmology, University of Iceland, Reykjavik, Iceland.
authors: Evelien
authors: E
authors: Vandewalle
authors: L
authors: L
authors: Abegão Pinto
authors: Olof B
authors: OB
authors: Olafsdottir
authors: Eline
authors: E
authors: De Clerck
authors: Peter
authors: P
authors: Stalmans
authors: Joachim
authors: J
authors: Van Calster
authors: Thierry
authors: T
authors: Zeyen
authors: Einar
authors: E
authors: Stefánsson
authors: Ingeborg
authors: I
authors: Stalmans
mesh_terms: D001794:Blood Pressure / Q000502:physiology; D005260:Female; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D010313:Partial Pressure; D011446:Prospective Studies; D012165:Retinal Ganglion Cells / Q000473:pathology*; D012171:Retinal Vessels / Q000503:physiopathology*; D014054:Tomography; D014065:Tonometry, Ocular; D014786:Vision Disorders / Q000097:blood; D058609:Visual Field Tests; D014794:Visual Fields
chemical_list: D010100:Oxygen
keywords: glaucoma; oxygen; retinal oximetry; structural parameters; visual field test