Macular Degeneration images—the black spot can be small and grow larger
Age-related macular degeneration, often called AMD or ARMD, is the leading cause of vision loss and blindness among Americans who are age 65 and older. Because people in this group are an increasingly larger percentage of the general population, vision loss from macular degeneration is a growing problem. (http://www.allaboutvision.com/conditions/amd.htm)
Stargardts is very similar to Macular Degeneration but occurs in younger ages…
While macular degeneration generally is associated with aging eyes, an inherited form known as Stargardt's disease can affect children and young adults.
Stargardt's disease — also called fundus flavimaculatus or Stargardt's macular dystrophy (SMD) — affects approximately one in 10,000 people and is characterized by central vision loss early in life. (Some researchers believe a distinction should be made between Stargardt's disease and fundus flavimaculatus, because they say each describes a different variant of the eye disease.) http://www.allaboutvision.com/conditions/stargardts.htm
See images here: Macular Degeneration and Stargardts