11 A cataract clouds the lens of the eye, limiting vision. In a normal eye, light passes through the lens to be focused on the retina. The retina is the eye's light-sensitive layer that sends signals to the brain that are interpreted as vision. To produce a sharp image, the lens must remain clear. The lens is made mostly of water and protein.
Protein arranges itself to allow light rays to pass through and to focus the rays onto the retina.
Sometimes protein clumps together, clouding small areas of the lens and blocking some light from reaching the retina. This clouding is called a cataract. The rate of cataract progression can be unpredictable. Some cataracts will worsen significantly within a few weeks. Others remain unchanged for many years.