Age-related macular degeneration (AMD) is the leading cause of poor vision in people over 60. When the macula degenerates, central vision is gradually lost. Peripheral (side) vision normally remains so AMD does not lead to total blindness. The degeneration usually involves both eyes, though it may start in one eye and not affect the other eye until much later.
The macula is the tiny area in the retina that provides sharp central vision. Though the macular area is no larger than a pinhead, it contains the visual cells for seeing straight ahead, fine detail, and color. If the macula is damaged — or degenerates, as from AMD — central vision is interfered with. So when you look at an object, part of it may seem distorted, blotted out, or shrouded in a dark haze.
Scientists have not yet learned why a macula that has functioned well for most of your life begins to degenerate. Heredity is likely to play a role, as well as years of exposure to bright sunlight. It is also possible that tissue changes accompanying the normal aging process somehow interfere with the macula’s getting enough oxygen. Smokers and former smokers have been found to have a much higher risk of AMD, though stopping smoking does not reverse the degeneration or even slow it down. Other risk factors are hypertension and heart disease. Some studies have found a relationship to a high intake of saturated fat, but those findings are not conclusive. AMD is not caused by using your eyes too much.