Macular degeneration, ophthalmoscope image. Numerous yellow drusen spots are seen on the retina, the light-sensitive membrane that lines the back of the eyeball. The macula is the area of the retina responsible for central vision, which is the sharpest. It is not known what causes macular degeneration, although old age, poor nutrition and overexposure to the ultraviolet radiation in sunlight have all been implicated. The main symptom is a loss of central vision, meaning reading and delicate tasks become difficult or impossible. Some distortion of peripheral vision may also occur. There is no effective treatment for this kind of degeneration.