Focus What is the Best Method to Evaluate Retinal Microcirculation?

The microvasculature of retinal ganglion cell layer, which is the part of central nervous system, can be investigated non-invasively in human. For clinical routine the fluorescence angiography is used to test patency and leak of retinal or choroid vessels, and to determine the blood passage time through the capillaries, but not to measure microperfusion. The first non-mydriatic Heidelberg Retina Flowmetry with Scanning Laser Doppler Flowmetry (SLDF) technology using perfusion image analysis software AFFPIA has enabled simultaneously reliable examination of retinal microperfusion (RCF) and arteriolar morphology (inner and outer vessel diameters) with calculation of wall-thickness, wall-to-lumen-ratio (WLR), mean distance between vessels with 10–20mm diameter, calculation of retinal microperfusion resistance coefficient by RCF and mean arterial pressure, and the estimation of changes of the parameters depends on heart pulsation. Retinal arterioles morphology can be measure by adaptive optics technology. In real time correlating to heart beat retinal microperfusion was illustrated by Laser Speckle Flowgraphy. Perfusion in retinal arterioles and venules was studied using dual beam Fourier-domain Doppler optical coherence tomography. Non-mydriatic cameras and scanning laser ophthalmoscopy enable quantification of arteriole-to-venule diameter ratio (AVR) or oxygen saturation in retinal vessels. In studies exploring retinal microperfusion the crucial parameters can be obtained using SLDF.