Overt and harmful diabetes mellitus (DM) has detrimental effects on individuals and, by extension, the community. Among the microvascular DM complications is diabetic retinopathy (DR). DR may cause irreversible vision deterioration in cases of poor blood glucose regulation. Changes in vascular permeability are key trigger points for diabetic macular edema (DME), a condition characterized by the accumulation of fluid in the macula. The development of vascular endothelial growth factor (VEGF) pathway inhibitors has provided a pathogenesis-based treatment approach for DME. Optical coherence tomography (OCT) provides high-resolution imaging of the anatomy, including the aging of DME and its structural damage, in distinct morphologic subtypes of macular edema, thereby supporting the assessment of macular edema treatment. The availability of repeated OCT monitoring provides clinical reassurance through the treatment. OCT angiography (OCTA) provides retinal blood flow maps with high spatial resolution. The ability promotes an understanding of disease pathogenesis and facilitates the implementation of new therapeutic methods. This review compares the potential of OCT and OCTA in the diagnosis and treatment of DME, as well as their respective therapeutic applications.