Perfusion-Map Variations Demonstrate the Activity of the Retinal Autoregulation System in the Human Retina

Abstract

Optic-nerve head and retinal perfusion were measured in 26 normal volunteers, in 28 hypertensive patients (in the preperimetric period of the evolution of glaucoma) and in 24 patients with advanced glaucoma (perimetric period). Patients were examined with the Heidelberg Retina Flowmeter, and flow, volume and velocity indices were assessed in each report. Perfusion maps were reconstructed based on 12 different acquisitions of each optic-nerve head and adjacent retina in order to cover a larger area. Result: Normal patients showed relatively normal perfusion indices, while hypertensive eyes (glaucomatous patients in the preperimetric period) showed significantly increased perfusion values in relation to the control group (p< 0.001). Patients with advanced glaucoma (in the perimetric period) showed significantly decreased values (p< 0.001) in relation to both groups. Conclusions:(1) During exposure to high intraocular pressure, retinal blood flow increases due to stimulation of autoregulation.(2) When this exposure is longer, autoregulation might not be able to preserve blood flow, thus leading to its decrease. (3) Autoregulation seems to have a “point of no return” if intraocular pressure is too high or if exposure is too long.