The principal symptom of macular degeneration is reduction or loss of central vision, with retention of peripheral vision. About 85 - 90% of ARMD cases are the dry, or atrophic, form, in which yellowish spots of fatty deposits called drusen appear on the macula. The rest of age-related macular degeneration cases are the wet form, so called because of leakage into the retina from newly forming blood vessels in the choroid, a part of the eye behind the retina. Normally, blood vessels in the choroid bring nutrients to, and carry waste products away from, the retina. Sometimes the fine blood vessels in the choroid underlying the macula begin to proliferate, a process called choroidal neovascularization. The cause is unknown. When those blood vessels proliferate, they leak, and cells in the macula are damaged and killed. The principal symptom of macular degeneration is reduction or loss of central vision, with retention of peripheral vision.