As drusen accumulate, they can cause inflammation. Inflammatory cellsInflammatory cells
a cell participating in the inflammatory response to a foreign substance. are recruited to the retina. These cells and the retinal epithelial cells begin releasing proteins and inflammatory cytokines that cause blood vessels to grow. The primary growth factor released is called vascular endothelial growth factor (VEGF) Vascular endothelial growth factor (VEGF)
Family of proteins that stimulates the growth of new blood vessels—there are four members of the VEGF family, designated -A, -B, -C, -D in humans; VEGF-A is the target for most anti-VEGF therapies, and excess levels of these factors cause new vessels to be leaky.