Quantify absolute choroidal blood flow with speckle imaging

Blood flow measurements are important in many applications, especially in the retina. In the clinic, flow is typically imaged with optical coherence tomography angiography (OCTA), fluorescein angiography or laser speckle contrast imaging. While conventional non-invasive imaging modalities can visualize flow, they cannot determine the absolute flow without information about the angle between the flow and the probing beam. Typically, two or three beams are required in OCTA to determine the absolute flow. Measurements on the flow phantom demonstrated our speckle imaging system can quantify the absolute flow independent of the angle between the vessel and the imaging system. Measurements in the human eye demonstrate the method can measure the flow in the upper layers of the retina, and in choroidal blood vessels below the photoreceptors-retinal pigment epithelium-Bruch's membrane complex.