title: Effect of increased oxygen tension on flicker-induced vasodilatation in the human retina.
abstract: In the retina, blood flow and neural activity are tightly coupled. Stimulation of the retina with flickering light is accompanied by an increase in blood flow. The current study seeks to investigate whether an increase in oxygen tension modulates flicker (FL)-induced vasodilatation in the human retina. A total of 52 healthy volunteers were included. Via a breathing mask, 100% oxygen (O(2)) was administered in one, a mixture of 8% carbon dioxide and 92% oxygen (C/O) in a second cohort. Retinal vessel diameters were measured with a Vessel Analyzer and FL responses were assessed before and during the breathing periods. At baseline, FL stimulation increased retinal vessel diameters by +3.7±2.3% in arteries and by +5.1±3.7% in veins. Breathing of C/O led to a decrease in arterial (-9.0±6.9%) and venous (-11.3±5.9%) vessel calibers. Flicker response was increased to 5.7±2.5% in arteries and to 8.6±4.1% in veins. Breathing of pure O2 induced a vasoconstriction of vessel diameters by -14.0±5.3% in arteries and -18.4±7.0% in veins and increased FL responses in arteries (+6.2±2.8%) and veins (+7.2±3.1%). Systemic hyperoxia increases FL-induced retinal vasodilatation in the retina. The mechanism by which oxygen modulates the hyperemic response to FL stimulation remains to be elucidated.
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Palkovits
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Told
authors.affiliation: 1] Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria [2] Center of Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Agnes
authors.initials: A
authors.lastname: Boltz
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Doreen
authors.initials: D
authors.lastname: Schmidl
authors.affiliation: Department of Ophthalmology, Emergency University Hospital, Bucharest, Romania.
authors.forename: Alina
authors.initials: A
authors.lastname: Popa Cherecheanu
authors.affiliation: 1] Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria [2] Center of Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Leopold
authors.initials: L
authors.lastname: Schmetterer
authors.affiliation: Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Garhöfer
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000097:blood; D005260:Female; D006801:Humans; D018496:Hyperoxia / Q000503:physiopathology; D017078:Laser-Doppler Flowmetry; D008297:Male; D010092:Oximetry; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood*; D010313:Partial Pressure; D010775:Photic Stimulation; D012039:Regional Blood Flow / Q000502:physiology; D012160:Retina / Q000378:metabolism; D012161:Retinal Artery / Q000502:physiology*; D012169:Retinal Vein / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology*; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen