Retinal Microvascular Disease in Diabetes and Its Prognostic Utility for Cardiovascular and Renal Complications: A Comprehensive Literature Review.

Retinal microvascular impairments are recognized as a non-invasive measure of systemic vascular injury in patients with diabetes. Change in retinal structure and function may serve as markers of renal and cardiovascular microvascular pathology, thereby providing a potential source of prognostic information for predicting outcomes of diabetic kidney disease (DKD), chronic kidney disease (CKD), and cardiovascular disease (CVD). The study design of a comprehensive literature review was selected. The literature review was conducted using the systematic approach of PRISMA 2020 guidelines. However, the study design is a literature review. The literature review aimed to synthesize the current evidence using a narrative approach to the relationship between retinal microvascular parameters and renal and cardiovascular outcomes in patients with diabetes. Cross-sectional, case-control, randomized controlled, and prospective cohort studies published between January 1, 2000, and December 31, 2025, were included after the literature search. We conducted the literature search and screening in compliance with the PRISMA 2020 guidelines to ensure transparency and reproducibility. The review indicates that broader retinal venules, constriction of arterioles, decreased fractal dimension, failed circulation inside the fovea, and expanded foveal avascular zone were considerably associated with the augmented danger of DKD, albuminuria, and lost estimated glomerular filtration rate (eGFR). In several longitudinal cohort studies, diabetic retinopathy at moderate-to-severe levels, but not at mild, fully explained incident CVD and stroke, as well as coronary events and all-cause mortality. Synergistic outcomes were a development of the coexistence of retinal abnormalities and microalbuminuria, with a risk of up to seven times that of cardiovascular events. Nonetheless, certain studies identified no or weak correlations when traditional risk factors were adjusted, underscoring the variability in predictive efficacy. The study concluded that retinal microvascular predictors, particularly diabetic retinopathy severity and imaging parameters, have strong potential to predict non-invasive renal and cardiovascular outcomes in diabetes. These results support the notion of the retina as a window into microvascular health within the systemic circulation. Future, large-scale studies using standardized imaging modalities are warranted to determine the additional prognostic value of retinal biomarkers in risk-stratification models for diabetic complications.