A cataract is cloudiness (opacification) that develops within the natural lens of your eye. This blurry vision is a normal part of the aging process.
Your eye's natural lens focuses light on your retina and allows you to see things sharply. The lens functions best when you are younger because it is crystal clear. As you age, the lens slowly turns yellow, then brown; it then becomes opaque and blocks the image entering the eye.
An analogy of a cataract is a window that is never washed. As dirt accumulates, the window loses its clarity, and it is no longer possible to see through it. Similarly, a cataract can progress to the point that vision decreases.
Age is not the only cause of cataracts, however. Other causes of cataracts include:
