Each eye has a lens — a window made of clear protein and water that sits behind the pupil. The lens focuses light onto the retina, which sends it to your brain. As you get older, the proteins change and parts of your lens turn cloudy. This is known as a cataract. It can make things look blurry or give them a brownish tint. Cataracts are a leading cause of blindness, especially in older people. But they can be corrected through surgery — a procedure that’s done more than 2 million times a year in the United States.