title: Relation of retinal blood flow and retinal oxygen extraction during stimulation with diffuse luminance flicker.
abstract: Cerebral and retinal blood flow are dependent on local neuronal activity. Several studies quantified the increase in cerebral blood flow and oxygen consumption during activity. In the present study we investigated the relation between changes in retinal blood flow and oxygen extraction during stimulation with diffuse luminance flicker and the influence of breathing gas mixtures with different fractions of O2 (FiO2; 100% 15% and 12%). Twenty-four healthy subjects were included. Retinal blood flow was studied by combining measurement of vessel diameters using the Dynamic Vessel Analyser with measurements of blood velocity using laser Doppler velocimetry. Oxygen saturation was measured using spectroscopic reflectometry and oxygen extraction was calculated. Flicker stimulation increased retinal blood flow (57.7 ± 17.8%) and oxygen extraction (34.6 ± 24.1%; p < 0.001 each). During 100% oxygen breathing the response of retinal blood flow and oxygen extraction was increased (p < 0.01 each). By contrast, breathing gas mixtures with 12% and 15% FiO2 did not alter flicker-induced retinal haemodynamic changes. The present study indicates that at a comparable increase in blood flow the increase in oxygen extraction in the retina is larger than in the brain. During systemic hyperoxia the blood flow and oxygen extraction responses to neural stimulation are augmented. The underlying mechanism is unknown.
authors.affiliation: Department of Clinical Pharmacology Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Palkovits
authors.affiliation: Department of Clinical Pharmacology Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Lasta
authors.affiliation: Department of Clinical Pharmacology Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Told
authors.affiliation: Department of Clinical Pharmacology Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.
authors.forename: Doreen
authors.initials: D
authors.lastname: Schmidl
authors.affiliation: Department of Clinical Pharmacology Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.|Center for Medical Physics and Biomedical Engineering Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.
authors.forename: René
authors.initials: R
authors.lastname: Werkmeister
authors.affiliation: Department of Ophthalmology, Emergency University Hospital 169, Splaiul Independentei St., District 5, Bucharest, Romania.
authors.forename: Alina Popa
authors.initials: AP
authors.lastname: Cherecheanu
authors.affiliation: Department of Clinical Pharmacology Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Garhöfer
authors.affiliation: Department of Clinical Pharmacology Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.|Center for Medical Physics and Biomedical Engineering Medical University of Vienna Waehringer Guertel 18-20, 1090 Vienna, Austria.
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
mesh_terms: D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D001783:Blood Flow Velocity / Q000502:physiology; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D012039:Regional Blood Flow / Q000502:physiology; D012119:Respiration; D012160:Retina / Q000502:physiology*; D012171:Retinal Vessels / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen