A cataract is a clouding of the lens in the eye leading to a decrease in vision. It can affect one or both eyes. Symptoms may include faded colors, blurry vision, halos around light, trouble with bright lights, and trouble seeing at night. This may result in trouble driving, reading, or recognizing faces. Cataracts are the cause of half of blindness and 33% of visual impairment worldwide. Cataracts are most commonly due to aging, but may also occur due to trauma, radiation exposure, be present from birth, or occur following eye surgery for other problems.Either clumps of protein or yellow-brown pigment may be deposited in the lens reducing the transmission of light to the retina at the back of the eye. Diagnosis is by an eye examination. . Early symptoms may be improved with eyeglasses. If this does not help, surgery to remove the cloudy lens and replace it with an artificial lens is the only effective treatment. Surgery is only needed if the cataracts are causing problems. Surgery generally results in an improved quality of life.