Effects of changes in arterial Po2 and Pco2 on the electroretinogram in the cat

Abstract

Changes in components of the electroretinogram during hyperoxia, hypoxia, and hypercapnia were studied to demonstrate retinal vascular autoregulation by electrophysiologic means. Autoregulation of the retinal arterial network is shown to stabilized the b-wave during hyperoxia (arterial PO2 of 395 mm Hg). During marked hypoxia, under ventilation with 10% and 5% O2, the b-wave decreased, indicating failure of autoregulation at the corresponding arterial PO2 levels of 30 and 26 mm Hg. During hypercapnia, possible autoregulatory effects were counteracted by a low arterial pH, which decreased the b-wave amplitude. The findings provide new electrophysiologic evidence for autoregulation of the retinal vessels. The c-wave during changes in arterial PO2 and PCO2 underwent changes that correlate inversely with fluctuations in blood pressure that occurred during ventilation with test gas mixtures. Considering the linear relationship between blood pressure and choroidal flow, we suggest that the latter influences the amplitude of the c-wave.