A cataract is a clouding of the natural lens inside the eye. A cataract is a gradual thickening of the lens that causes the lens to become so clouded that light is either distorted or cannot reach the back of the eye (the retina) for transmission to the brain. When left untreated, cataracts will eventually cause blindness in most cases.
Advanced technology lenses (multi-focal and accommodating lenses), which reduce your need for glasses following cataract surgery, are an exciting new option!