Systemic Hypoxia Increases Retinal Blood Flow but Reduces the Oxygen Saturation Less in Peripheral Than in Macular Vessels in Normal Persons.

Purpose: Retinal vascular diseases are characterized by regional differences in the distribution of morphological lesions that may be related to regional differences in the autoregulation of retinal blood flow. The purpose of the present study was to investigate how systemic hypoxia affects blood flow and oxygen saturation in different vascular areas in normal persons. Methods: In 28 normal persons, oxygen saturation and vessel diameters were measured by dual wavelength retinal oximetry, and blood flow velocity by Doppler OCT in the peripapillary arterioles supplying and venules draining the four retinal quadrants, and in an arteriolar and a venular branch from the upper temporal arcade towards respectively the retinal periphery and the macular area. The measurements were performed during normoxia and during breathing of a gas mixture containing 12.5% oxygen. Results: Systemic hypoxia reduced the oxygen saturation in peripapillary arterioles by approximately 11% (P < 0.001) and increased the peripapillary blood flow by approximately 40% (P < 0.001). Systemic hypoxia also reduced the oxygen saturation in the macular arterioles and venules and in the peripheral arterioles (P < 0.003), but not in the peripheral venules (P = 95). The blood flow increased significantly in both macular and peripheral arterioles and venules (P < 0.04). Conclusions: Systemic hypoxia can affect the venous oxygen saturation in vessels draining the retinal periphery and the macular area differently. The findings may help to understand the regionally varying manifestations of retinal vascular disease.