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Rene Werkmeister, Doreen Schmidl, Gerold Aschinger, Veronika Doblhoff-Dier, Stefan Palkovits, Magdalena Wirth, Gerhard Garhofer, Leopold Schmetterer; Retinal oxygen extraction in humans. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4398.
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© ARVO (1962-2015); The Authors (2016-present)
Optimal function of the retina is dependent on adequate oxygen supply. In humans, the inner retina including the retinal ganglion cells is oxygenated via the retinal circulation. We present a method to calculate total retinal oxygen extraction based on non-invasive techniques in humans.
In a total of 8 healthy subjects, absolute retinal blood flow values and optical density ratio for each retinal vessel entering the optic nerve head were assessed using dual-beam bidirectional Doppler Optical Coherence Tomography (OCT) and spectrophotometric measurements, respectively. These experiments were done during breathing of ambient room air as well as during breathing of 100% oxygen. Based on these measurements, retinal oxygen extraction was calculated.
Total retinal blood flow was 44.3 ± 3.0 ml/min during baseline and decreased to 18.7 ± 4.2 µl/min during 100% oxygen breathing (P < 0.001). Corrected arterio-venous oxygen difference was 0.053 ± 0.008 [ml(O2)/ml] at baseline and 0.048 ± 0.011 [ml(O2)/ml] during systemic hyperoxia (P < 0.01). This resulted in a pronounced decrease in retinal oxygen extraction from 2.33 ± 0.51 μl(O2)/min during breathing of room air to 0.88 ± 0.14 µl(O2)/min during breathing of 100% oxygen.
The present study indicates that total retinal oxygen extraction is significantly reduced during 100% oxygen breathing most likely because oxygen from the choroid is delivered towards the inner retina under these conditions. The proposed method may have significant potential to study oxygen metabolism in hypoxic retinal diseases such diabetic retinopathy.
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