title: Chorioretinal vascular oxygen tension changes in response to light flicker.
abstract: OBJECTIVE
  To investigate oxygen tension (P(O2)) changes in the retinal and choroidal vasculatures in response to visual stimulation by light flicker.
  
  
  METHODS
  A previously developed optical section phosphorescence imaging system was used to measure P(O2) separately in the retinal veins, arteries, and capillaries and in the choroid before and during light flicker. Imaging was performed in rats during light flicker at frequencies between 0 and 14 Hz. Light flicker-induced changes in the chorioretinal vasculature P(O2) and arteriovenous P(O2) differences were determined. Retinal arterial and venous P(O2) were measured along blood vessels as a function of the distance from the optic nerve head.
  
  
  RESULTS
  Retinal arterial P(O2) and arteriovenous P(O2) differences increased with increasing light flicker at frequencies up to 10 Hz, after which no further increase was observed. Significant increases in retinal arterial P(O2) (P = 0.009; n =10) and in retinal capillary P(O2) (P = 0.04, n = 10) were measured in response to light flicker at 10 Hz. Retinal arteriovenous P(O2) differences during light flicker were significantly greater than differences before light flicker (P = 0.01; n = 10). Retinal arterial P(O2) decreased significantly with increased distance from the optic nerve head (P < or = 0.004), whereas retinal venous P(O2) remained relatively unchanged (P > or= 0.4).
  
  
  CONCLUSIONS
  Measurement of changes in the chorioretinal vasculature P(O2) can potentially advance the understanding of oxygen dynamics in challenged physiological states and in animal models of human retinal diseases.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago (UIC), 1855 West Taylor Street, Chicago, IL 60612, USA.
authors.forename: Akbar
authors.initials: A
authors.lastname: Shakoor
authors.forename: Norman P
authors.initials: NP
authors.lastname: Blair
authors.forename: Marek
authors.initials: M
authors.lastname: Mori
authors.forename: Mahnaz
authors.initials: M
authors.lastname: Shahidi
mesh_terms: D000818:Animals; D002829:Choroid / Q000098:blood supply*; D008163:Luminescent Measurements; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000528:radiation effects*; D010313:Partial Pressure; D010775:Photic Stimulation; D051381:Rats; D020318:Rats, Long-Evans; D012039:Regional Blood Flow / Q000528:radiation effects; D012160:Retina / Q000528:radiation effects*; D012171:Retinal Vessels / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D010100:Oxygen