Retinal blood flow derived from dye dilution curves: Televised fluorescein angiography

A television system was used to record retinal fluorescein dilution curves. In pigs, fluorescein was injected intravenously (IV), into the left ventricle (ILV), and ILV during bilateral carotid occlusion (ILVco). Dye dilution curves from points on a retinal-artery-vein pair, from two points on a single artery, and from two points on a single vein were recorded by a storage oscilloscope, using two photodetectors positioned over the television image of the vessels. Dye curves were less dispersed following ILV than following IV injections, and were irregular following ILVco injection. The dye appearance time was shortest after injection with ILV and progressively longer with ILVco and IV. The artery-vein mean transit time was greatest during carotid occlusion. Retinal blood flow in a venous segment was calculated to be 0.149 +/- 0.037 mi/min. This value was reproducible following both IV and ILV injections but could not be obtained following ILVco due to irregularity of the curves. It was in the same range as that found (0.095 +/- 0.011 ml/min), using the radioactively labeled microsphere technique. The system was subsequently tested in humans and was found to give reproducible dye curves. The usefulness of the system as a clinical tool is presently being explored.