Resistive index of central retinal artery is a bioimaging biomarker for severity of diabetic retinopathy

BACKGROUND: The present study was undertaken to assess the resistive index (RI) of central retinal artery (CRA) as a bioimaging biomarker for the severity of diabetic retinopathy (DR), for the first time. METHODS: Eighty-one consecutive patients of type 2 diabetes mellitus between the ages of 40 and 70 years were included in a tertiary care center-based cross sectional study. Severity of retinopathy was assessed according to Early Treatment Diabetic Retinopathy Study (ETDRS) classification: diabetes mellitus with no retinopathy (No DR) (n = 26); non-proliferative diabetic retinopathy (NPDR) (n = 29); and proliferative diabetic retinopathy (PDR) (n = 26). Twenty-six healthy controls of similar age were also included. Resistive index of CRA was studied using color Doppler and gray scale sonography. Central subfield thickness (CST), cube average thickness (CAT), retinal photoreceptor ellipsoid zone (EZ) disruption, and retinal nerve fiber layer (RNFL) thickness were evaluated using spectral domain optical coherence tomography. Sensitivity and specificity were assessed by receiver operating characteristic (ROC) curve. RESULTS: Mean RI of CRA for the study groups revealed significant increase with severity of diabetic retinopathy (F = 10.24, P < 0.001). The ROC curve analysis showed diagnostic accuracy of RI of CRA (area under curve = 0.841–0.999; sensitivity = 76–100%, specificity = 95.45–100%, P < 0.001) in discriminating controls and patients. Univariate regression analysis revealed significant association between the study groups and RI of CRA (P < 0.001). RI of CRA correlated positively with CST (r = 0.37), CAT (r = 0.45), EZ disruption (r = 0.43) and negatively with RNFL thickness (r = − 0.35) (P < 0.001). CONCLUSIONS: Resistive index of CRA is a reliable bioimaging biomarker for the severity of DR.