Abstract
Purpose :
Changes in the arterial blood pressure induce compensatory changes in the diameter of retinal arterioles in order to maintain the retinal blood flow constant. It is unknown to what extent the oxygen saturation in the larger retinal vessels is affected by this autoregulation.
Methods :
Twenty normal persons, age (mean±SD, range) 30.1±3.7, 24-37 years were subjected to dual wave-length retinal oximetry (model T1, Oxymap, Reykjavik, Iceland) and Doppler OCT measurement (Medical University, Vienna, Austria) of the retinal blood flow before and 30 seconds after having started isometric exercise by lifting a hand weight of 2 kg. The changes in the diameter, the oxygen saturation and the linear velocity of the blood induced by the increase in the arterial blood pressure were assessed.
Results :
The isometric exercise increased the mean arterial blood pressure with (mean±SD) 10±5.0 mmHg which induced a contraction of (mean±SD) 4.9% ± 9.2% (p<0.001) in the arterioles and 4.4%± 9.1% (p<0.001) in the venules. The linear velocity increased (mean±SD) 33.9% ± 94.7% (p=0.003) in the arterioles and 38.9% ±100.6% (p=0.001) in the venules, which implied that the change in volume flow was unchanged in both the arterioles (p=0.9) and in the venules (p=0.8). The retinal oxygen saturation in the arterioles was reduced non-significantly by (mean±SD) 0.02% ± 3.2% (p=1.0) whereas the oxygen saturation in the larger retinal venules increased significantly by (mean±SD) 8.1% ± 6.6% (p<0.001).
Conclusions :
An increase in the arterial blood pressure induced by isometric exercise reduces oxygen extraction in the retinal microcirculation. This may partially be due to shunting of blood to bypass the retinal microcirculation.
This is a 2020 ARVO Annual Meeting abstract.