(A) An illustrated schematic of normal retina compared with nonproliferative diabetic retinopathy (NPDR) with diabetic macular edema (DME). The normal healthy retina includes healthy retinal blood vessels, glial elements including Müller cells, neuronal elements including photoreceptors, and resting microglia. The inner and outer blood-retinal barriers are intact. In contrast, the retina in diabetic retinopathy exhibits multiple abnormalities, including vascular changes (microaneurysms, venous beading, capillary degeneration, and neovascularization), lesions associated with vascular damage (cotton wool spots and exudate), glial dysfunction including Müller cell swelling, neuronal damage, activated microglia, retinal pigment epithelium (RPE) damage, and thinning of the choriocapillaris. There is dysfunction of the inner and outer blood-retinal barrier, with resulting accumulation of fluid in the retina, which can be manifested by thickening of retinal layers, cysts, and subretinal fluid. (B) Color fundus photograph and OCT images of a normal healthy retina and retina with severe NPDR with central-involved DME are shown. Illustrated by Rachel Davidowitz.