DPP4 and diabetes mellitus: This decline in visually impaired cases associated with diabetic retinopathy in Japan may be attributed to advancements in diabetes mellitus and diabetic retinopathy treatments, such as the introduction of intravitreal injection of anti-vascular endothelial growth factor (VEGF) agents, systemic administration of dipeptidyl peptidase-4 (DPP-4) inhibitors, sodium-glucose co-transporter-2 (SGLT2) inhibitors, and glucagon-like peptide-1 (GLP-1) receptor agonists, as well as improvements in vitrectomy systems [4].