Understanding the Third Eyelid in Cats

by beaconpet
What Is the Third Eyelid in a Cat?

Did you know that cats have more than just two eyelids on each eye? In addition to the upper and lower eyelids, there is a third eyelid that you usually don’t see. However, in some cases, a protruding third eyelid can actually be a sign of illness or injury. This article will help you understand what a third eyelid in cats is and why it may appear. From drowsiness to conjunctivitis, we’ll explore the different reasons why your cat’s third eyelid appears and discuss when to seek veterinary advice. Don’t delay learning more about this fascinating aspect of your cat’s health! For more follow BEACONPET.

What Is the Third Eyelid in a Cat?

What Is the Third Eyelid in a Cat?

Cats have more than just two eyelids on each eye. In addition to the upper and lower eyelids, there is a third eyelid that is normally not visible. This third eyelid is called the nictitating membrane and is located in the corner of each eye towards the center of the face. It is typically retracted and not easily seen. However, in some cases, the third eyelid may protrude and partially cover the eyeball.

Reasons for a Cat’s Third Eyelid to Appear

It is uncommon to see your cat’s third eyelid, and its appearance may indicate that there is something wrong. There are several reasons for a protruding third eyelid in cats, some of which are normal while others may be problematic. If you notice your cat’s third eyelid protruding for more than a few hours, it is recommended to contact your veterinarian for further evaluation.

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Sleepiness or Relaxed State

One common reason for the third eyelid to appear is when a cat is in a very relaxed or tired state. You may notice that the third eyelids are visible while your cat is sleeping or right after waking up. This is normally nothing to worry about as the third eyelid should retract as soon as the cat becomes awake and more alert. However, if the third eyelid stays up for a prolonged period of time, it would be best to consult with your veterinarian just to be safe.

Sedation or Anesthesia

If your cat has undergone a medical procedure that required sedation or anesthesia, it is not uncommon for the third eyelid to appear and partially cover the eye due to extreme physical relaxation. This effect may last for several hours after waking but should gradually go away. It is considered normal and not a cause for concern unless the third eyelid remains up after the day of the procedure.



Conjunctivitis, also known as “pink eye,” is the inflammation of the conjunctiva, which is the thin, transparent mucous membrane that lines the inside of the eyelids and covers the front part of the eye. This condition may be caused by an infection, allergies, injury, or an eye irritant. Inflammation and protrusion of the third eyelid are not uncommon in cats with conjunctivitis. Treatment typically involves medicated eye drops or ointment that contain antibiotics and/or steroids.

Corneal Ulcers

Corneal ulcers are wounds to the cornea, which is the clear covering of the eye, including the iris and pupil. These ulcers can cause pain, inflammation, and the appearance of the third eyelid. They are usually caused by an injury to the eye, such as a scrape, scratch, or puncture wound, and may also be triggered by irritating or abrasive substances. Corneal ulcers require veterinary treatment, which may involve various eye medications and possibly oral medications as well.

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Uveitis is the inflammation of the uvea, which is the middle part of the eyeball containing many blood vessels. This condition often causes redness in the eye and can sometimes affect the third eyelid. Uveitis may be accompanied by pain. Prompt veterinary attention is necessary for proper diagnosis and treatment.



Glaucoma is a painful eye condition characterized by increased pressure within the eye. It occurs when the fluid within the front part of the eye, known as the aqueous humor, is unable to drain properly. Inflammation of the third eyelid may sometimes accompany glaucoma. This condition requires immediate veterinary attention to prevent further damage to the optic nerve and potential blindness.

Cherry Eye

The third eyelid contains a gland that can become swollen and protrude from the inner corner of the eye, resembling a round mass. This condition is known as prolapse of the nictitating membrane, or cherry eye. While relatively uncommon in most cats, it is more frequently seen in Burmese cats. Surgery is usually required to treat cherry eye.

Eye Growths

Growths, tumors, masses, and cysts in and around the eye can cause inflammation and protrusion of the third eyelid. If you notice any abnormal growth or swelling in or around your cat’s eye, it is important to contact your veterinarian for an examination and appropriate treatment.

Horner’s Syndrome

Horner’s syndrome is a neurological disorder that can affect the eyes and facial muscles, resulting in asymmetrical appearance of the eyes. The third eyelid is often very prominent in one eye, and the affected eye may appear droopy or “sunken in.” Horner’s syndrome can be caused by trauma or a tumor, although sometimes the underlying cause may not be determined. The condition may resolve on its own or require specific treatment.

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What to Do If You See Your Cat’s Third Eyelid

If you notice your cat’s third eyelid protruding and it doesn’t seem to be caused by sleep, relaxation, sedation, or anesthesia, it is important to contact your veterinarian as soon as possible for further advice. It may be a sign of an underlying health issue that requires attention. If your cat is showing other signs of illness, it is recommended to bring your cat to the vet for a thorough examination. Avoid attempting to put anything in the eye without your vet’s recommendation, as this can potentially worsen the condition. Eye problems can quickly escalate, so it is crucial not to delay in seeking veterinary care.

What Your Cat Is Saying With Its Eyes

What Your Cat Is Saying With Its Eyes

Cats often communicate through body language, including their eyes. Paying attention to your cat’s eye movements and expressions can provide insight into their emotional state. Dilated pupils can indicate excitement or fear, while narrowed pupils may indicate aggression, stress, or discomfort. Slow blinking is often a sign of relaxation and trust. If you notice any sudden or significant changes in your cat’s eye appearance or behavior, it is advisable to consult with your veterinarian for a proper evaluation and guidance.

Remember, your cat’s health and well-being are important, and any concerns regarding their eyes should be addressed promptly by a veterinary professional.

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