Association Between Carotid Intima-Media Thickness and Severity of Diabetic Retinopathy

Background: Diabetic retinopathy (DR) is a microvascular complication of diabetes, while increased carotid intima-media thickness (CIMT) reflects subclinical atherosclerosis. Evidence regarding their association in northern Iraq remains limited. Aim: To determine the association between CIMT and the presence and severity of DR among adults with type 2 diabetes mellitus. Methods: This hospital-based cross-sectional study included 144 adults with type 2 diabetes attending Azadi Teaching Hospital, Kirkuk, Iraq, from January 2024 to June 2026. DR was graded using dilated fundus examination and color fundus photography. Bilateral CIMT was measured using B-mode ultrasonography. Participants were classified as no DR (n=42), mild-to-moderate non-proliferative DR (n=61), or severe non-proliferative/proliferative DR (n=41). Results: Mean age was 57.8±8.9 years, and 54.17% were male. Mean CIMT increased progressively from 0.70±0.11 mm in patients without DR to 0.82±0.14 mm in mild-to-moderate DR and 0.96±0.17 mm in severe/proliferative DR (p<0.001). Carotid plaque prevalence increased from 11.90% to 27.87% and 48.78%, respectively (p<0.001). CIMT correlated with DR severity (rho=0.58; p<0.001). After multivariable adjustment, each 0.10-mm increase in CIMT was associated with greater odds of severe/proliferative DR (adjusted OR=1.48; 95% CI: 1.16–1.90; p=0.002). Conclusion: Increased CIMT and carotid plaque burden were independently associated with greater DR severity, supporting an association between retinal microvascular disease and systemic vascular injury in type 2 diabetes.