The macula is the point of the retina on which light rays are focused by the cornea and the lens of the eye. Like the film in a camera, the retina is responsible for transforming focused light into an image which the brain can process. If the macula is damaged, the central part of the image is blocked out or blurred, while the image around the blurred area may be unaffected.
Macular degeneration is a group of chronic diseases which cause breakdown of the macular tissues.
It does not cause complete blindness, but can make reading or close work very difficult or impossible. Although macular degeneration often occurs in older people, age alone is not the only reason for central visual loss. It is caused by thinning or breakdown of tissues in and beneath the macula. Normal blood vessels have strong walls and do not leak, but these vessels are brittle, and cause fluids to accumulate under the retina, impairing its function. Sometimes they rupture and bleed, leading to scar tissue which impairs the function of the macula severely.