CCL2 and macular retinal edema: There is good correlation between the increasing abundance of inflammatory markers, such as IL-1B, IL-6, IL-8, MCP-1, and IP-10, and the Early Treatment Diabetic Retinopathy Study (ETDRS) severity score of diabetic retinopathy.46,47 In contrast, VEGF-A levels are quite elevated in the aqueous humor even in diabetic eyes with little retinopathy, and rise modestly with increasing disease severity, before the onset of macular edema.47 However, macular edema is accompanied by substantial elevation of IL-6 and MCP-1 as well as VEGF-A.