Cataracts Think of how hard it is to see through a frosty window in winter.
Similarly, the lens of the eye can become fogged, or opaque, resulting in decreased vision. The lens lies behind the iris and is about the size and shape of an aspirin tablet. A cataract is the name given to the clouding of the normally clear lens. This clouding blocks light from the retina. Cataracts are one of the most common causes of impaired vision in the world.