My 20 yr old cat is having eye problems. He is diabetic and I administer insulin once a day. He is also on diabetic diet.
He has had eye infections since the onslaught of the diagnosis of diabetes. Today I noticed his left eye had his tear duct covering half of his eye??! What is this?
Hi Elle… what you are seeing is the nictitating membrane or third eyelid.
The third eyelid is not normally seen. It may become visible in response to illness.
It protrudes from the inside corner of the eye, where the tear duct is. That is probably why you mistook it
for the tear duct.
When only one eye has a protruding third eyelid it is probably caused by an illness that is related to that eye only.
Whereas if the third eyelid is seen in both eyes suspect a general illness such as feline viral respiratory infection.
There are many possible eye diseases. In this case it is due to an eye infection in the left eye it seems.
It may be caused by a corneal abrasion. The cornea may be abraded by eyelashes that are in the wrong position. The third eyelid comes out to protect the scratched cornea.
Recommended: see the vet to have it checked out.