Nerve Damage Causes Horner’s Syndrome

Horner’s syndrome doesn’t require treatment but the cause of it should be identified.

Horner's syndrome, which usually occurs in only one eye, is characterized by an abrupt onset of drooping of the upper eyelid; elevation of the nictitans, or third eyelid, which looks like a white film; retraction of the eyeball deeper into its socket; and constriction of the pupil so it remains small. Natdanai99/Shutterstock

Q: Hobie, my middle-aged indoor-outdoor cat, awoke this morning with one very abnormal eye. His upper lid droops, and a white film covers the inside corner of the eye. What caused this? Will it resolve on its own, or should I take Hobie to his veterinarian?

A: I'd advise a trip to the vet. It sounds like Hobie has Horner’s syndrome, which is not a specific disease but the name of a group of clinical signs.