NOS3 and non-proliferative diabetic retinopathy: Abbreviations: DR, diabetic retinopathy; NPDR, non-proliferative diabetic retinopathy; STDR, sight-threatening diabetic retinopathy; PDR, proliferative diabetic retinopathy; VEGF, vascular endothelial growth factor; AMPK, AMP-activated protein kinase; eNOS, endothelial nitric oxide synthase; RPE, retinal pigment epithelium; ROS, reactive oxygen species; T2D, type 2 diabetes; mTORC1, mechanistic target of rapamycin complex 1; pS6, phosphorylated ribosomal protein S6; aHR, adjusted hazard ratio.