Hemorrhage Segmentation in Fundus Images Using the U-Net 3+ Model: Performance Comparison Across Retinal Regions.

Diabetic retinopathy (DR) is one of the most common complications of diabetes, and timely detection of retinal hemorrhages is essential for preventing vision loss. This study evaluates the U-Net3 + model for pixel-level hemorrhage segmentation in fundus images and examines its performance across clinically meaningful retinal regions. Model performance was assessed using accuracy, sensitivity, specificity, and Dice score and further analyzed across perivascular and extravascular areas, perifoveal and extrafoveal regions, fovea-centered quadrants, and images stratified by hemorrhage burden. U-Net3 + achieved strong overall performance, with 99.93% accuracy, 87.03% sensitivity, 99.97% specificity, and an 85.02% Dice score. Higher segmentation accuracy was observed in extravascular regions and within the foveal area, while quadrant-wise performance remained largely consistent. Images with greater hemorrhage burden demonstrated higher segmentation reliability. These findings highlight the importance of region-aware evaluation and suggest that U-Net3 + can provide clinically meaningful support for automated DR screening. Further validation using larger and multi-center datasets is required to enhance the model's generalizability for real-world clinical deployment.