title: The Effects of Diabetic Retinopathy Stage and Light Flicker on Inner Retinal Oxygen Extraction Fraction.
abstract: OBJECTIVE
  We determined the effects of light flicker and diabetic retinopathy (DR) stage on retinal vascular diameter (D), oxygen saturation (SO2), and inner retinal oxygen extraction fraction (OEF).
  
  
  METHODS
  Subjects were categorized as nondiabetic control (NC, n = 42), diabetic with no clinical DR (NDR; n = 32), nonproliferative DR (NPDR; n = 42), or proliferative DR (PDR; n = 14). Our customized optical imaging system simultaneously measured arterial and venous D (DA, DV) and SO2 (SO2A, SO2V) before and during light flicker. Inner retinal OEF was derived from SO2 values. Light flicker-induced ratios of metrics (DAR, DVR, SO2AR, SO2VR, OEFR) were calculated.
  
  
  RESULTS
  Arterial D was larger in NPDR compared to NC (P = 0.01) and PDR (P = 0.002), whereas DV was similar among groups (P ≥ 0.16). Light flicker increased DA and DV (P ≤ 0.004), but DAR and DVR were similar among groups (P ≥ 0.09). Arterial SO2 was higher in all groups compared to NC (P ≤ 0.02) and higher in PDR compared to NDR and NPDR (P<0.001). Arterial SO2 did not change with light flicker (P ≥ 0.1). Venous SO2 was higher in NPDR and PDR compared to NC and NDR (P ≤ 0.02). Light flicker increased SO2V in NC, NDR, and PDR (P ≤ 0.003), and SO2VR was lower in NPDR compared to NC and NDR (P ≤ 0.05). Inner retinal OEF was lower in NPDR compared to NDR and PDR (P ≤ 0.02). Light flicker decreased OEF (P ≤ 0.03), but OEFR was greater in NPDR compared to NC and NDR (P ≤ 0.03).
  
  
  CONCLUSIONS
  The findings of alterations in retinal D, SO2, OEF, and their light flicker-induced responses at stages of DR may be useful to elucidate the pathophysiology of DR.
authors: Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.
authors: Anthony E
authors: AE
authors: Felder
authors: Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.
authors: Justin
authors: J
authors: Wanek
authors: Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.
authors: Norman P
authors: NP
authors: Blair
authors: Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States 2School of Public Health, Division of Epidemiology and Biostatistics, University of Illinois at Chicago, Chicago, Illinois, United States 3University of Illinois Cancer Center, Population Health, Behavior, and Outcomes Program, Chicago, Illinois, United States.
authors: Charlotte E
authors: CE
authors: Joslin
authors: School of Public Health, Division of Epidemiology and Biostatistics, University of Illinois at Chicago, Chicago, Illinois, United States.
authors: Katherine C
authors: KC
authors: Brewer
authors: Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.
authors: Felix Y
authors: FY
authors: Chau
authors: Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.
authors: Jennifer I
authors: JI
authors: Lim
authors: Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.
authors: Yannek I
authors: YI
authors: Leiderman
authors: Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.
authors: Mahnaz
authors: M
authors: Shahidi
mesh_terms: D000328:Adult; D000368:Aged; D003930:Diabetic Retinopathy / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D033401:Microscopy, Acoustic; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D010775:Photic Stimulation; D012171:Retinal Vessels / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D010100:Oxygen