Definition:

Macular degeneration is the physical breakdown of the central portion of the retina called the macula. Age-related macular degeneration (AMD/ARMD) is the leading cause of blindness. AMD is a complex disease caused by the combination of genetic predisposition and environmental factors. Using genome linkage scan and association studies, multiple potentially causative genes have been identified. In AMD, there are two phenotypes, atrophic/ dry and neovascular/ wet. The former is characterized by the geographic atrophy due to death of retinal pigment epithelium, and the latter is usually characterized by the abnormal growth of new blood vessels under the macula, which causes severe loss of vision. While wet AMD can be treated by the inhibition of vascular endothelial growth factor or photodynamic therapy, so far there are no available treatments for dry AMD.