Several groups have reported that 100% oxygen breathing caused an increase in retinal venous oxygen saturation. In the present study we set out to study the effects of 100% oxygen breathing on retinal blood flow and retinal oxygen saturation to gain more insight into the regulation of retinal oxygenation.Methods
30 healthy volunteers were included into the present study. The effect of 100% oxygen breathing on retinal blood velocities was performed using laser Doppler velocimetry (LDV). Retinal vessel diameters were measured with the Dynamic Vessel Analyzer (DVA, Imedos, Germany). Retinal oxygen saturation was evaluated in retinal arteries and retinal veins using spectroscopy also employing the DVA. The effect of 100% oxygen breathing on systemic oxygen tension was evaluated based on arterialized blood samples drawn from the earlobe.Results
Breathing 100% oxygen caused systemic hyperoxia as evidenced from a pronounced increase in systemic oxygen tension (p < 0.001). Oxygen saturation increased in both retinal arteries and retinal veins (p < 0.05 each) but the effect in veins was more pronounced. As expected we observed a decrease in retinal vessel diameters, retinal blood velocities as well as in retinal blood flow (p < 0.001 each).Conclusion
The results are compatible with the idea that increased venous oxygen saturation during 100% oxygen breathing is due to a pronounced decrease in retinal blood flow. In addition, our data indicate unchanged retinal oxygen extraction during hyperoxia.