title: Reproducibility and sensitivity of scanning laser Doppler flowmetry during graded changes in PO2.
abstract: OBJECTIVE
  Recently a commercially available scanning laser Doppler flowmeter has been produced, which provides two dimensional maps of the retinal perfusion. The aim of the present study was to investigate the reproducibility and the sensitivity of these measurements.
  
  
  METHODS
  16 healthy subjects were randomised to inhale different gas mixtures of oxygen and nitrogen in a double blind crossover study. The following gas mixtures of oxygen and nitrogen were administered: 100% oxygen + 0% nitrogen, 80% oxygen + 20% nitrogen, 60% oxygen + 40% nitrogen, 40% oxygen + 60% nitrogen, 30% oxygen + 70% nitrogen, 20% oxygen + 80% nitrogen, 15% oxygen + 85% nitrogen, and 10% oxygen + 90% nitrogen. Retinal haemodynamic variables and systemic haemodynamics were measured during all inhalation periods. Recordings under resting conditions were performed three times to calculate intraclass coefficients.
  
  
  RESULTS
  In two subjects we did not obtain technically adequate results. A dose dependent change in retinal blood flow during graded oxygen breathing was observed (p < 0.001). During 100% oxygen breathing blood flow decrease was between 29% and 33%, whereas blood flow increase was between 28% and 33% during inhalation of 10% oxygen + 90% nitrogen.
  
  
  CONCLUSIONS
  Scanning laser Doppler flowmetry has an acceptable reproducibility and is appropriate for description of the effect of graded changes in PO2 on retinal haemodynamics. The main problems with the system are the large zero offset, the fixation during retinal scanning, and the neglect of blood flow changes during the cardiac cycle.
authors.affiliation: Department of Ophthalmology B, University of Vienna, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Strenn
authors.forename: R
authors.initials: R
authors.lastname: Menapace
authors.forename: G
authors.initials: G
authors.lastname: Rainer
authors.forename: O
authors.initials: O
authors.lastname: Findl
authors.forename: M
authors.initials: M
authors.lastname: Wolzt
authors.forename: L
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001783:Blood Flow Velocity / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D018496:Hyperoxia / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D017078:Laser-Doppler Flowmetry / Q000379:methods* / Q000592:standards; D008297:Male; D010100:Oxygen / Q000502:physiology*; D010313:Partial Pressure; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000502:physiology*; D012680:Sensitivity and Specificity
chemical_list: D010100:Oxygen