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Editors Selection IGR 8-4
Bloodflow: Bloodoxygen saturation
Comment by Alon Harris on:
16844 Oxygen saturation in optic nerve head structures by hyperspectral image analysis, Beach J; Ning J; Khoobehi B, Current Eye Research, 2007; 32: 161-170
This is an original and interesting publication. Beach et al. (172) measured blood oxygen saturation in optic nerve head (ONH) arteries, veins, and capillaries at normal and elevated IOP in a primate model. They found surprising low levels of arterial and venous blood oxygen saturation at baseline (81.8% and 42.6% respectively) with 68.3% oxygen saturation in capillaries within the tissue of the ONH. Increasing IOP from the baseline value of 10mmHg to 55mmHg reduced blood oxygen saturation in both large vessels and capillaries. In addition to monitoring blood pressure and heart rate during the experiment, the authors could have employed a pulse oximeter. This might have provided a reference standard for the primary outcome parameters; provided the validity of the assumption that arterial blood oxygen saturation is similar throughout the arterial system. Further, the induction of ischemia via increased IOP might be expected to result in decreased oxygen saturation in blood in both large vessels and capillaries; however, the effect could easily have been confirmed within the test animals with a similar peripheral ischemia and a pulse oximeter. Interpretation of the study data would have been enhanced with a simple parallel measurement of systemic oximetry.
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