One reason for the insignificant VEGF staining changes after treatment is that bevacizumab can only inhibit the expression of VEGF in a short time frame, as the plasma-free VEGF level markedly decreased within the first week after bevacizumab injection in human AMD patients, but later it increased again (Avery et al., 2017). This evidence concerns the gene VEGFA and age-related macular degeneration.