macular degeneration, eye disorder causing loss of central vision. The affected area, the macula, lies at the back of the retina and is the part that produces the sharpest vision. The most serious visual impairment occurs when abnormal blood vessels form and leak serous fluid or bleed into the tissue of the macula, ultimately producing scar tissue. Peripheral (side) vision is unaffected. Onset may be acute with hemorrhage but usually is gradually progressive. Although some vision is retained, the ability to read, recognize faces, and drive a motor vehicle is greatly reduced. The condition is painless.