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Continuous measurements of intra-vascular pO2 in the pig optic nerve head
S D Cranstoun1, C E Riva, J L Munoz
1Institut de Recherches en Ophtalmologie, Sion.
Background:
The measurement of oxygen concentration in the microvasculature of a tissue is important for the understanding of oxygen delivery.
Material And Methods:
A technique was developed to measure in a continuous manner the partial pressure of oxygen (pO2) in the optic nerve microvasculature of the minipig. This technique is based on the quenching by oxygen of the phosphorescence emitted by a dye that is injected intravenously. It provides measurements of the intra-vascular pO2 and was applied simultaneously with measurements of the extra-vascular pO2 with microelectrodes and blood flow by laser Doppler flowmetry.
Results:
We demonstrate for the first that the optic nerve head intra-vascular pO2 increases during dark adaptation. Furthermore no change in extra-vascular pO2 and blood flow could be detected.
Conclusions:
Based on Krogh's model, these results suggest that oxygen consumption by the optic nerve head tissue increases during dark adaptation.