prognosis. In addition, these can be applied in clinical trials as endpoints. Late AMD In late AMD, enough retinal damage occurs that, in addition to drusen, people will also begin to experience symptomatic central vision loss. The damage can either be the development of atrophy or the onset of neovascular disease. Late AMD is further divided into two subtypes based on the types of damage: Geographic atrophy and Wet AMD (also called Neovascular AMD). Dry AMD Dry AMD (also called nonexudative AMD) is a broad designation, encompassing all forms of AMD that are not neovascular (wet AMD). This includes early and intermediate forms of AMD, as well as the advanced form of dry AMD known as geographic atrophy. Dry AMD patients tend to have minimal symptoms in the earlier stages; visual function loss occurs more often if the condition advances to geographic atrophy. Dry AMD accounts for 80–90% of cases and tends to progress slowly. In 10–20% of people, dry AMD progresses to the wet type. Geographic atrophy Geographic atrophy (also called atrophic AMD) is an advanced form of AMD in which progressive and irreversible loss of retinal cells leads to a loss of visual function. There are multiple layers that make up the retina, and in geographic atrophy, there are three specific layers that undergo atrophy: the choriocapillaris, retinal pigment epithelium, and the overlying photoreceptors. The three layers that undergo atrophy in geographic atrophy are all adjacent to each other. The photoreceptors are the most superficial and they are the cells that are responsible for converting energy from the light from the outside world, into an electrical signal to be sent to the brain. There are several functions of the retinal pigment epithelium. One of the main functions of the retinal pigment epithelium is to minimize oxidative stress. It does so by absorbing light, and thus preventing it from getting to the underlying layers. The layers underlying the retinal pigment epithelium are very vascularlized so they have very high oxygen tension. Thus, if light was to get to those layers, many free radicals would form and cause damage to nearby tissues. The deepest layer that undergoes atrophy in geographic atrophy is called the choriocappilaris. It is a capillary network that provides nutrients to the retinal pigment epithelium. The pathophysiology of geographic atrophy is still uncertain. Some studies questioned whether it was due to a deficient retinal pigment epithelium, leading