title: Hyperspectral imaging for measurement of oxygen saturation in the optic nerve head.
abstract: OBJECTIVE
  To evaluate a hyperspectral imaging technique for monitoring relative spatial changes in retinal oxygen saturation.
  
  
  METHODS
  The optic nerve head (ONH) and overlying vessels in cynomolgus monkey eyes were imaged with a fundus camera attached to a hyperspectral imaging system. Images were acquired with inspiration of room air and pure oxygen and at controlled intraocular pressures (IOP) of 15 mm Hg (normal) and 60 mm Hg (sustained for up to 5 minutes). Changes in relative blood oxygen saturation in the vessels and ONH were assessed from reflectance spectra. Saturation maps were derived from contributions of oxygenated and deoxygenated hemoglobin spectral signatures extracted from hyperspectral images. The results obtained with hyperspectral imaging were compared with known experimental outcomes.
  
  
  RESULTS
  Pure oxygen markedly increased oxygen saturation in veins. Increases in arteries and the ONH were smaller. The results obtained with hyperspectral image analysis agreed with known changes in oxygen saturation from breathing experiments. Raising IOP reduced saturation in all structures and resulted in profound desaturation of arteries. During sustained high IOP, a rebound in saturation was observed in the ONH. Spatial maps clearly showed the saturation changes in arteries, veins, and surrounding tissues.
  
  
  CONCLUSIONS
  Hyperspectral imaging can be adapted to measure and map relative oxygen saturation in retinal structures and the ONH in nonhuman primate eyes.
authors.affiliation: LSU Eye Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA. bkhoob@lsuhsc.edu
authors.forename: Bahram
authors.initials: B
authors.lastname: Khoobehi
authors.forename: James M
authors.initials: JM
authors.lastname: Beach
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kawano
mesh_terms: D000818:Animals; D005451:Fluorescein Angiography; D007429:Intraocular Pressure; D008252:Macaca fascicularis; D009898:Optic Disk / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology*; D010108:Oxyhemoglobins / Q000378:metabolism; D010781:Photography / Q000379:methods; D012039:Regional Blood Flow; D012171:Retinal Vessels / Q000502:physiology*; D013057:Spectrum Analysis
chemical_list: D010108:Oxyhemoglobins; D010100:Oxygen