Based on published studies on macrophages/microglia activation leading to inflammation (37), we proposed that increased expression of the complement components, VEGF, other cytokines, and ECM components (MMPs) in the vitreous of ROP patients are mediated by macrophage/microglia activation by creating an imbalance of angiogenic and anti-angiogenic molecules (Figure 5). Here, VEGFA is linked to retinopathy of prematurity.