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G. Garhofer, G. Weigert, H. Resch, L. Schmetterer; Effect of Oxygen Breathing on Flicker Induced Vasodilatation in the Human Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2259.
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It has been shown that increased neural activity evoked by stimulation with diffuse luminance flicker increases retinal and optic nerve head blood flow. Beside others, an increased oxygen demand has been attributed to evoke the flicker response. This study seeks to investigate whether the flicker light induced increase in retinal vessel diameters is different in subjects breathing 100% oxygen compared to subjects breathing room air.
10 healthy volunteers were included in the study. Diameters of retinal vessels were recorded continuously with a Retinal Vessel Analyzer. During this measurement flicker stimulation was applied at a frequency of 8 Hz. Flicker responses were assessed before and during breathing of 100% oxygen. Blood gas values were determined from capillary blood samples.
Under room air conditions flicker stimulation increased retinal vessel diameters by +2.0±1.2% in retinal arteries and by +1.4±0.8% in retinal veins. Breathing of oxygen increased pO2 from 85±5 mmHg to 390±80 mmHg. Arterial diameter decreased by -9±8%, retinal venous diameters by -15±6% during the breathing period (p<0.01 each). No significant change in flicker response was observed during breathing oxygen compared to baseline conditions (arteries: 2.1±2.0%, veins: 1.1±1.0%).
Oxygen breathing leads to a pronounced constriction of retinal vessels. Additionally, breathing of oxygen does not alter the response of retinal vessels to stimulation with flicker light. This indicates that systemic hyperoxia does not modulate flicker responses in retial vessels.
www.trialregister.nl/trialreg/index.asp NTC00312390 recruitment started in 2004
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