Investigation of the retinal neurovascular networks through modulation of blood oxygen levels in humans

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Introduction: The human retina is comprised of neurons that relay visual information to the brain. An effective distribution of oxygen to the different layers of the retina is required to support their structural and functional integrity. The retinal and choroidal vasculatures insure proper oxygen distribution to neural tissue. Oxygen delivery to a tissue is strongly dependent on the arterial oxygen concentration. Experimentally, it is possible to modify the arterial oxygen level by modifying the oxygen or carbon dioxide concentrations in inspired air. Objective: To quantify changes in the responsiveness of retinal neurons and their blood supply to carefully controlled changes in the normal concentration of oxygen in blood. Scientific approach: The bio-electrical responses representing the activity of the principal retinal neurons will be monitored non-invasively through the flash electroretinogram a-wave, b-wave and oscillatory potentials, as well as the pattern evoked electroretinogram. Global and focal blood flow in the retina, and blood flow in discrete vessels and capillary beds will be recorded with dedicated systems. These measurements will be carried out during alterations in the degree of oxygenated arterial blood. Expected significance: This research will provide new insights into the dependence of normal retinal function on the degree of oxygenation in the blood perfusing the anatomically distinct retinal layers. This knowledge is essential if we are to understand the vascular role in retinal diseases, particularly those associated with retinal ischemia.