The lens of the eye sits behind the colored iris; its job is to bend light rays to produce a sharply focused image upon the retina. New lens fibers are constantly being formed by cells in the outer portion of the lens called the lens capsule. As new lens fibers are formed, older fibers cannot exit the lens capsule so get pushed toward the lens center. Unfortunately with time and aging, this process turns the crystal-clear lens cloudy due to the compressed fibers. This process is called lenticular or nuclear sclerosis.
Lenticular sclerosis is simply a hardening and thickening of the lens fibers. The lens becomes blue-gray, and the pupil appears cloudy. Occasionally owners will think the cloudiness comes and goes, but this is more likely due to alterations in the size of the pupil based on lighting conditions – rather than any actual change in cloudiness. In other words, the lens stays cloudy but a larger pupil diameter allows you to see more of the hazy lens color. Lenticular sclerosis does not cause blindness though in advanced cases depth perception and near vision may be less accurate.
Animals usually retain enough vision to function well within a familiar environment. No treatment is required unless a true cataract (opacification of the lens) forms, in addition to lenticular sclerosis.