title: Noninvasive assessment of retinal vascular oxygen content among normal and diabetic human subjects: a study using hyperspectral computed tomographic imaging spectroscopy.
abstract: OBJECTIVE
  This pilot study was aimed to demonstrate the clinical feasibility of using hyperspectral computed tomographic spectroscopy to measure blood oxygen content in human retinal vessels.
  
  
  METHODS
  All procedures were performed under a University of Southern California Institutional Review Board-approved protocol and after obtaining informed consent. Fifty-seven subjects with and without diabetic retinopathy were dilated for standard fundus photography. Fundus photographs and retinal vascular oxygen measurements (oximetry) were made using a custom-made hyperspectral computed tomographic imaging spectrometer coupled to a standard fundus camera. Oximetry measurements were made along arteries (Aox) and veins (Vox) within vessel segments that were 1 to 2 disk diameters from the optic disk.
  
  
  RESULTS
  For all control subjects (n = 45), mean Aox and Vox were 93 ± 7% and 65 ± 5% (P = 0.001), respectively. For all diabetic subjects (n = 12), mean Aox and Vox were 90 ± 7% and 68 ± 5% (P = 0.001), respectively. In subjects with proliferative diabetic retinopathy, Aox was significantly lower, and Vox was significantly higher than other groups (85 ± 4% and 71 ± 4%, respectively; P = 0.04, analysis of variance). There was a highly significant difference in the arteriovenous difference between subjects with proliferative diabetic retinopathy and those in the control group (14 vs. 26%, P = 0.003).
  
  
  CONCLUSIONS
  Hyperspectral computed tomographic spectroscopy is a clinically feasible method for measurement and analysis of vascular oxygen content in retinal health and disease. This study uses the techniques relevant to oximetry; however, the breadth of spectral data available through this method may be applicable to study other anatomical and functional features of the retina in health and disease.
authors.affiliation: *Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, California; †Reichert Technologies, Buffalo, New York; and Departments of ‡Neuroscience, and §Biomedical Engineering, University of Southern California, Los Angeles, California.
authors.forename: Amir H
authors.initials: AH
authors.lastname: Kashani
authors.forename: Gilberto R
authors.initials: GR
authors.lastname: Lopez Jaime
authors.forename: Saloomeh
authors.initials: S
authors.lastname: Saati
authors.forename: Gabriel
authors.initials: G
authors.lastname: Martin
authors.forename: Rohit
authors.initials: R
authors.lastname: Varma
authors.forename: Mark S
authors.initials: MS
authors.lastname: Humayun
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001786:Blood Glucose / Q000378:metabolism; D003930:Diabetic Retinopathy / Q000503:physiopathology*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D005451:Fluorescein Angiography; D006442:Glycated Hemoglobin / Q000378:metabolism; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000097:blood*; D010865:Pilot Projects; D012171:Retinal Vessels / Q000503:physiopathology*; D013057:Spectrum Analysis; D014057:Tomography, X-Ray Computed
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; D010100:Oxygen; C517652:hemoglobin A1c protein, human
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