Multi-exposure laser speckle perfusion imaging for retinal blood flow

Abstract

Measurements of flow in retinal vessels is presented and compared with in vitro measurements on whole blood in capillaries ranging from 75 to 200µm diameter. The viewing angle of the capillaries and their range of size allows sizedependent effects to be investigated when estimating flow within actual vessels.Retinal measurements show a pulse effect. When this is removed by synchronisation, multi-exposure measurements show different spectral signature from single speed scatterers. Multi-exposure measurements of the retina demonstrate a varying contribution of stationary scatter across the field. Unlike scattering in dermal tissue, photons in retinal vessels must return by multiple scatter from moving Red Blood Cells, whose motion is directed. Speckle estimates of flow in retinal vessels are therefore possible.