Retinal blood flow and its autoregulation measured by intraocular hydrogen clearance

Retinal blood flow (RBF) was measured with polarographic electrodes at the inner retinal surface using the hydrogen clearance technique. This new intraocular technique allowed repeated and reproducible measurements of retinal blood flow. Usually the clearance curves were monoexponential, indicating that hydrogen clearance in only one compartment, the retina, was being measured. In order to quantitatively describe the autoregulation of retinal blood flow with oxygen tension, the retinal blood flow was measured at levels of arterial blood oxygen tension ranging from 20 to 250 mmHg. The retinal blood flow was found to decrease progressively with increased arterial blood oxygen tension. Linear regression analysis showed a statistical fit (P less than 0.01) between retinal blood flow and arterial blood oxygen tension (PaO2): RBF (ml min-1 100 g-1)-1 = 79.2-0.17 x PaO2 (mmHg)-1. The average blood flow in the cat was found to be 56 +/- 10 ml min-1 100 g-1 (mean +/- 1 S.D., n = 11) at an average arterial blood oxygen tension of 128 mmHg.