Abstract Purpose: This study investigated retinal blood flow alterations in diabetic macular edema (DME) using ultra-widefield optical coherence tomography angiography (OCTA). Methods: We enrolled 31 healthy controls (NC, 56 eyes), 40 diabetes patients without diabetic retinopathy (DM, 79 eyes), 25 non-proliferative diabetic retinopathy patients (NPDR, 47 eyes), and 42 DME patients (DME, 54 eyes).