A cataract is the formation of a cloudy screen over the natural lens which is normally clear, located immediately behind the colored section of our eye, but for any reason loses its transparency, becomes cloudy and impairs vision. According to the degree of the cataract in eyes affected by the disease, this can begin as slightly clouded vision, and reach a level where only light is visible. Cataract, the most common cause of blindness in the world, is a loss of sight that can be treated.