Respiratory Stress, Visual Function and Moderation by Chemotherapy

Based upon the accepted sensitivity of visual function, particularly the peripheral visual fields, to moderate changes in circulating oxygen subsequent to work at altitude and/or respiratory distress, studies were undertaken to determine the sight in the visual system of changes and the influence of blood factors upon these changes. In an animal model, controlled hypoxia, blood gas measures, and measures of electrical signals at various stages of the visual pathway were correlated. Findings were: there is a threshold effect for short term hypoxia where visual function is altered first between 10-12% inspired O2; retinal action potentials are the most sensitive indicators of the onset of hypoxic visual loss with changes at the optic nerve and the visual cortex following; blood PaO2 is only partially correlated with the rate of visual loss and recovery; and buffering of blood pH provides for protection from visual loss under hypoxic conditions which would otherwise produce functional deficits. Cumulative effects of hypoxia relating to visual function and the extent to which buffering can control visual functional losses requires additional research.