A cataract is a condition where the lens of the eye loses its clarity, becomes clouded and affects vision. Clouding causes the lens to become yellowish-brown in color.
Lens is a transparent structure that lies behind the iris and the pupil and works like the lens of a camera. It helps focus light on the retina (light sensitive tissue at the back of the eye) to form an image. In normal condition since the lens is clear, you see a sharp image of the objects around you. In cataract, since the lens is not clear, the images you see are blurred. Most cataracts occur in older people and are age related. Cataract can affect one or both eye but it cannot spread from one eye to another.