NPPB and acute kidney injury: Analysis of the ROC curves (Fig. 2) showed no difference in performance for the prediction of AKI for retinal vascular density (area under the ROC curve (AUC) 0.745; 95% CI 0.649–0.841; P < 0.001), Mehran score (AUC 0.801; 95% CI 0.696–0.912; P < 0.001), NT-proBNP (AUC 0.794; 95% CI 0.688–0.899; P < 0.001), and the GRACE score (AUC 0.828; 95% CI 0.724–0.932; P < 0.001).