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	Description: Cataract, video illustration. A cataract is a clouding of the lens in your eye that affects vision. Most cataracts are related to aging. To understand how a cataract can affect your vision, it helps to understand a little about the structure of your eye. The lens is clear and lies between the iris and the pupil. It works much like a camera lens, focusing light, or an image, on the retina. The retina is the light-sensitive tissue at the back of the eye. Once the light or image reaches the retina, it is changed into nerve signals that are sent to the brain. Besides focusing light on the retina, the lens also adjusts the eye's focus, letting us see things clearly both up close and far away. The lens must be clear for the retina to receive a sharp image. The lens is made of mostly water and protein. The protein is arranged in a precise way that allows light to pass through it without distortion. But as we age, proteins in the lens clump together, causing a cataract. At first the protein may clump together and cloud in small area of the lens. Over time, the clumps may increase in size and number, clouding more of the lens. If the lens is cloudy from a cataract, the image you see will be blurred and colors may appear faded. Credit: National Eye Institute, National Institutes of Health View Animation (Quicktime) Ref#: VA08

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