FLT1 and retinal ischemia: The reason is that retinal ischemia and hypoxia in the occlusion area after BRVO promotes the strong expression of VEGF, which specifically binds to its receptors (VEGFR-1, VEGFR-2), increases vascular permeability, and upregulates the expression levels of VEGF, IL-6, ICAM-1, VCAM-1, and other inflammatory cytokines, leading to hypoxia-induced inflammation, and further aggravates the degree of ME through multiple positive feedback loops.