A clear lens inside the eye helps focus the external light on your retina. This lens also allows images to be sharply visible. As a person ages, this lens slowly grows cloudy and turns yellow. This clouding of the eye lens is a cataract. Cataracts are a commonly occurring problem that is caused by gradual overuse of ocular muscles. When the proteins that form the eye lens start to clump together, they block the light that optic nerves need to develop an image in the brain. Over time, the lens in your eye entirely clouds and ultimately hinders your vision.