CXCL8 and proliferative diabetic retinopathy: Levels of IL-6, IL-8, and monocyte chemoattractant protein-1 (MCP-1) are significantly elevated in the vitreous fluid in various vitreoretinal diseases, including diabetic macular edema, proliferative diabetic retinopathy, branch retinal vein occlusion, central retinal vein occlusion, and rhegmatogenous retinal detachment [21].