A cataract is a change in the texture and protein of the lens. Cataracts can lead to decreased vision to total inability to see images through the lens. These cataracts can also cause other health problems leading to irritation of tissue around the lens and glaucoma.
When your vet does a routine examination, they will check the eyes for normal and abnormal changes. If a cataract is noted, the course of treatment could vary from simply monitoring changes to medications and in some cases surgery.