title: Intervisit Repeatability of Retinal Blood Oximetry and Total Retinal Blood Flow Under Varying Systemic Blood Gas Oxygen Saturations.
abstract: OBJECTIVE
  The aim of the study is to validate and calibrate the Doppler spectral-domain optical coherence tomography (SD-OCT) derived total retinal blood flow (TRBF) and metabolic hyperspectral retinal camera (MHRC) derived oxygen saturation (SO2) of major retinal vessels in human volunteers using a novel and exact provocation technique (RespirAct) that allows the precise control of the end-tidal partial pressure of oxygen (PETO2). Between visit repeatability of the TRBF and retinal blood SO2 also were studied.
  
  
  METHODS
  One eye of 11 young healthy subjects was chosen randomly for the study. Total retinal blood flow and retinal SO2 measurements were obtained under conditions of normoxia, hyperoxia, and hypoxia. The order of hyperoxia and hypoxia was randomized between subjects. The measurements were repeated after a week interval.
  
  
  RESULTS
  When the arterial PETO2 was increased from baseline (PETO2 = 100 mm Hg) to 200 and 300 mm Hg, the TRBF significantly reduced (P = 0.02) from 44.60 (±8.9) to 40.28 (±8.9) and 36.23 (±4.6) μL/min. Lowering the arterial PETO2, from baseline to 80, 60, and 50 mm Hg, TRBF significantly increased (P = 0.04) from 43.17 (±12.7) to 45.19 (±5.5), 49.71 (±13.4), and 52.89 (±10.9) μL/min with simultaneous reduction in the arterial blood SO2 content from 99.3% (±5.8) to 95.6% (±5.1), 89.6% (±2.8), and 83.3% (±3.9), respectively (P = 0.00). The coefficient of repeatability (COR) of TRBF, retinal arterial, and venous blood SO2 values are 21.8 μL/min, 18.4%, and 15.2%, respectively.
  
  
  CONCLUSIONS
  Total retinal blood flow and retinal blood SO2 measurements performed under safe levels of hypoxia and hyperoxia were repeatable in healthy adults over the range of SO2 investigated.
authors.affiliation: School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Kalpana
authors.initials: K
authors.lastname: Rose
authors.affiliation: Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Susith I
authors.initials: SI
authors.lastname: Kulasekara
authors.affiliation: School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada 2Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Christopher
authors.initials: C
authors.lastname: Hudson
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D008297:Male; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology*; D012171:Retinal Vessels / Q000166:cytology / Q000502:physiology*; D041623:Tomography, Optical Coherence / Q000379:methods
chemical_list: D010100:Oxygen