title: Retinal blood flow during hyperoxia in humans revisited: concerted results using different measurement techniques.
abstract: Retinal vasculature shows pronounced vasoconstriction in response to hyperoxia, which appears to be related to the constant oxygen demand of the retina. However, the exact amount of blood flow reduction and the exact time course of this phenomenon are still a matter of debate. We set out to investigate the retinal response to hyperoxia using innovative techniques for the assessment of retinal hemodynamics. In a total of 48 healthy volunteers we studied the effect of 100% O(2) breathing on retinal blood flow using two methods. Red blood cell movement in larger retinal veins was quantified with combined laser Doppler velocimetry and retinal vessel size measurement. Retinal white blood cell movement was quantified with the blue field entoptic technique. The time course of retinal vasoconstriction in response to hyperoxia was assessed by continuous vessel size determination using the Zeiss retinal vessel analyzer. The response to hyperoxia as measured with combined laser Doppler velocimetry and vessel size measurement was almost twice as high as that observed with the blue field technique. Vasoconstriction in response to 100% O(2) breathing occurred within the first 5 min and no counterregulatory or adaptive mechanisms were observed. Based on these results we hypothesize that hyperoxia-induced vasoconstriction differentially affects red and white blood cell movement in the human retina. This hypothesis is based on the complex interactions between red and white blood cells in microcirculation, which have been described in detail for other vascular beds.
authors.affiliation: Department of Clinical Pharmacology, Department of Ophthalmology, University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Kiss
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Polska
authors.forename: Guido
authors.initials: G
authors.lastname: Dorner
authors.forename: Kaija
authors.initials: K
authors.lastname: Polak
authors.forename: Oliver
authors.initials: O
authors.lastname: Findl
authors.forename: Gabriele Fuchsjäger
authors.initials: GF
authors.lastname: Mayrl
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Eichler
authors.forename: Michael
authors.initials: M
authors.lastname: Wolzt
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002309:Cardiology / Q000379:methods*; D006439:Hemodynamics; D006801:Humans; D018496:Hyperoxia; D017078:Laser-Doppler Flowmetry; D008297:Male; D010100:Oxygen; D011674:Pulse; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000502:physiology*; D013997:Time Factors
chemical_list: D010100:Oxygen