Retinal Microvascular Alterations in Diabetic Patients Assessed with Novel Imaging Techniques

The global burden of diabetes mellitus and its chronic complications-including premature atherosclerotic cardiovascular disease and microvascular impairments such as nephropathy, retinopathy, and neuropathy-highlights the need for improved strategies for the early identification of individuals at risk of carbohydrate metabolism disorders. Growing evidence suggests that alterations in the microcirculatory bed occur concomitantly with, or may even precede, the development of cardiovascular disease. The eye, owing to its transparent anatomical structures, provides a unique opportunity for the in vivo assessment of microvascular changes and offers valuable insights into other vascular territories, serving as a potential "window" into cardiometabolic disorders. Recent advances in microcirculation imaging have enabled detailed, non-invasive evaluation of the retinal microvasculature. Techniques such as scanning laser Doppler flowmetry (SLDF), adaptive optics (AO), optical coherence tomography angiography (OCTA), and laser speckle flowgraphy (LSFG) allow for quantitative assessment of the retinal microvascular bed, demonstrating partial correlation with invasive measures of vascular function and sensitivity to therapeutic interventions. The integration of these imaging modalities into clinical and research settings may facilitate the early detection of microvascular dysfunction, improve risk stratification, and support the monitoring of disease progression and treatment efficacy in patients with carbohydrate metabolism disorders. Therefore, this review aims to summarize the current evidence on retinal microvascular alterations in carbohydrate metabolism disorders assessed using advanced imaging techniques, focusing primarily on early, subclinical retinal changes that precede the onset of diabetic retinopathy.