Feline Health • Eyes

Why is my cat's third eyelid showing?

The third eyelid normally sits mostly hidden at the inner corner of the eye. Persistent protrusion can occur with ocular pain, neurologic disease, dehydration, systemic illness, or certain bilateral syndromes.

Veterinarian reviewedUpdated Aug 20, 2026
The key takeaway

One eye versus both eyes, and whether the eye is painful, red, cloudy, or has an abnormal pupil, helps guide urgency.

Eye pain can raise the third eyelid

Corneal ulceration, inflammation, trauma, or other painful eye disease can cause the globe to retract slightly, making the third eyelid more visible. Squinting and redness increase concern.

What is Horner syndrome?

Horner syndrome is a neurologic condition that can cause a small pupil, drooping upper eyelid, sunken appearance of the eye, and protrusion of the third eyelid on the affected side. Causes vary and sometimes remain unidentified.

What is Haws syndrome?

Bilateral elevation of the third eyelids without obvious eye pain can occur in cats, sometimes in association with gastrointestinal disease. Diagnosis requires ruling out other causes.

When should the cat be seen?

Prompt examination is appropriate for a painful or cloudy eye, unequal pupils, trauma, sudden vision change, discharge, or persistent third-eyelid elevation. Eye disease can progress quickly and should not be treated with leftover steroid drops.