The Frequency of the Nonresponsiveness to Intravitreal Injection of the Anti-Vascular Endothelial Growth Factor Agent in Neovascular Age Related Macular Degeneration
Age-related macular degeneration (AMD) is a major cause of irreversible visual loss in developed countries in 65 years and older. The two types of AMD are non-neovascular type and neovascular type. Neovascular AMD is characterized by choroidal neovascular membrane (CNVM) that is due to the formation of abnormal blood vessels, which grow from the choroid into or under the retina. Although CNVM is present in only 10% of patients with AMD, it is responsible for 90% of cases with severe vision loss from hemorrhage and fibrosis. The pathogenesis of CNVM is a complex process involving the disturbance between proangiogenic and antiangiogenic factors. The vascular endothelial growth factor (VEGF) that released by retina pigment epithelium cells (RPE) is the most important of the angiogenic factors to stimulate the growth of new vessels. The formation of CNVM in AMD has been shown to be related to increase levels of VEGF. Anti-VEGF agents have drammatically improved the prognosis of patients with neovascular AMD.