Perspectives on diabetic retinopathy from advanced retinal vascular imaging

Diabetic retinopathy (DR) is a microvascular complication of diabetes and the most common cause of acquired vision loss in adults worldwide. DR is associated with long-term chronic hyperglycaemia and its detrimental effects on the neurovascular structure and function of the retina. Direct imaging of the retinal vasculature and staging of DR has been traditionally based on fundoscopy and fluorescein angiography, which provide only 2D views of the retina, and in the case of fluorescein angiography, requires an invasive dye injection. In contrast, advanced retinal imaging modalities like optical coherence tomography angiography (OCTA) and adaptive optics (AO) are non-invasive and provide depth-resolved, 3D visualization of retinal vessel structure as well as blood flow. Recent studies utilizing these imaging techniques have shown promise in evaluating quantitative vascular parameters that correlate tightly to clinical DR staging, elucidating functional changes in early diabetes, and monitoring DR treatment response. In this article, we discuss and synthesize the results of advanced retinal imaging studies in DR and their implications for our clinical and pathophysiologic understanding of the disease. Based on the recent literature, we also propose a model to describe the differential changes in vascular structure and flow that have been described on advanced retinal imaging as DR progresses. Future studies of these imaging modalities in larger and more diverse populations, as well as corroboration with histological and functional studies, will be important to further our understanding of DR.