eye disorders
Age Related Macular Degeneration (AMD or ARMD)
Pathophysiology of AMD
Two different forms occur: Dry (nonexudative or atrophic): All age-related macular degeneration (AMD) starts as the dry form. About 85% of people with AMD have only dry AMD. Wet (exudative or neovascular): Wet AMD occurs in about 15% of people. Although only 15% of patients with AMD have the wet form, 80 to 90% of the severe vision loss caused by AMD results from wet AMD. Dry AMDcauses changes of the retinal pigment epithelium, typically visible as dark pinpoint areas. The retinal pigment epithelium plays a critical role in keeping the cones and rods healthy and functioning well. Accumulation of waste products from the rods and cones can result in drusen, which appear as yellow spots. Areas of chorioretinal atrophy (referred to as geographic atrophy) occur in more advanced cases of dry AMD. There is no elevated macular scar (disciform scar), edema, hemorrhage, or exudation. Wet AMDoccurs when new abnormal blood vessels develop under the retina in a process called choroidal neovascularization (abnormal new vessel formation). Localized macular edema or hemorrhage may elevate an area of the macula or cause a localized retinal pigment epithelial detachment. Eventually, untreated neovascularization causes a disciform scar under the macula. 