Summary Diabetes and other retinal vascular diseases are a major cause of vision loss. This work builds on our measures of vascular remodeling in diabetes using adaptive optics (AO) retinal imaging. AO retinal imaging provides highly accurate and reproducible measures of both structural changes to the vascular walls of arterioles, and functional measures of blood flow and neurovascular coupling between visual stimulation and blood flow. By taking advantage of the precision of AO imaging we can make highly reproducible and accurate measurements of changes to retinal microvessels. In Aim 1 we will test the hypothesis that using a unique index of vascular wall damage which is insensitive to sampling biases can act as an index of diabetic damage. We will also generate a new measure of arteriole damage based on variability in the thickness of the vessel walls, presumably arising from endothelial and pericyte cell loss. We will then test whether these easily measured biomarkers are sensitive to local retinal ischemia, and can be used to measure progression of DR. Improving measurements in early DR is important as the clinical pathology is ultimately a consequence of these early changes. We will also test whether impaired neurovascular coupling is associated with these vascular changes. In Aim 2 we will measure early changes to the cone photoreceptors in diabetes, including both local areas of less reflective cones and regions of disordered cones and relate these changes to vascular changes. By also measuring visual sensitivity in areas with cone changes and those without we will test the hypothesis that imaging measurements can be used to understand the sensitivity changes occurring in DR. In Aim 3 we will for the first time, measure quantitative 3D flow maps of entire regions of the retinal vascular network. Flow maps include information as to where blood is flowing, velocity, size and in which direction allowing network quantification. Because the distribution of flow through a vascular network is sensitive to physical and biological constraints, flow maps will change markedly as capillary occlusion occur. By combining our state-of-the-art for retinal imaging of the vasculature with clinically available data we will continue to better understand the anatomical and functional basis for clinically observable damage. This work will advance our long term scientific goals of understanding the role that early vascular changes play in vision loss, our clinical goal of developing new approaches to identify those individuals most at risk for damage, as well as allow improved monitoring of future treatments on an individual basis.