The retina of the eye— one of the highly metabolic tissues in the body— relies upon an adequate supply of blood largely from choroidal circulation and to a small extent from retinal circulation for optimal retinal health. Impaired or reduced blood flow in either the retinal or the choroidal circulation triggers ischemic damage to the retina and subsequently leads to ischemic retinal diseases, such as diabetic retinopathy and age-related macular degeneration. Besides, choroidal blood flow is also indicated in the regulation of transient thickness changes in the choroid and in the maintenance of retinal temperature. However, the exact mechanisms underlying the pathogenesis of ischemic retinal diseases, choroidal thickness changes, and retinal thermoregulation are still unclear, as quantifying chorio-retinal blood flow remains challenging. Current ocular blood flow measurement techniques have several limitations and can only assess blood flow qualitatively. We have recently implemented a non-invasive arterial spin labeling (ASL) MRI technique to quantify blood flow in the human retina/ choroid complex. In this talk, I will provide an overview of this novel technique and discuss some of our research findings using ASL-MRI in relation to its potential clinical applications.