A cataract is a dense, cloudy area that forms in the lens of the eye. A cataract begins when proteins in the eye form clumps that prevent the lens from sending clear images to the retina.
The retina works by converting the light that comes through the lens into signals. It sends the signals to the optic nerve, which carries them to the brain.
It develops slowly and eventually interferes with your vision. You might end up with cataracts in both eyes, but they usually don’t form at the same time. This condition is common in older people.