Cherry eye in cats is a condition in which the third eyelid falls down or slips out of place and is then visible in the corner of the cat’s eye. Unlike people which only have 2 eyelids, cats have another eyelid that is normally invisible otherwise known as the nictitating membrane. The function of this third eyelid is to help protect and moisturize the eye through its tear gland.
Often the large red mass of tissue in the corner of the cat’s eye is the only symptom that the pet owner sees. Cherry eye rarely occurs in both eyes at a time; rather the cherry eye just pops out in one eye. The eyelid does not gradually slip out of place, it happens over a short period of time, and pet owners are often shocked to see that their cat which looked fine a few minutes ago now has a large red blob in the corner of the eye.
Cats and dogs both have a third eyelid, also known as a nictitans gland, which is responsible for tear production. In some instances this gland falls out of place and it becomes visible in the corner of the eye. Cherry eye is rare in cats, and it has been diagnosed mainly in Burmese and Persian cat breeds.