Why Is My Cat’s Third Eyelid Visible?

By helloBARK!
Updated on 26 September 2022
Expert Content

Is your cat’s third eyelid visible?

If this is the case, we recommend that you make an appointment with your vetenarian at the soonest available opportunity as it could be a sign of illness.

Indeed, all the experts in this article agree that calling your vet is the first step to take if you can see your cat’s third eyelid or you’re worried about the health of their eye.

Sometimes your cat’s third eyelid will be visible when your feline friend sleeps which shouldn’t be too alarming but is still worth talking to your vet.

However, if your four-legged friend’s third eyelid is constantly visible then it’s time to ring your vet and make an appointment.

In this article, we’ll speak to five experts about why your cat’s third eyelid might be visible and why it’s a good idea to speak to a professional.

Editor's note: The content on this website is meant to be informative in nature, but it should not be taken as veterinary, medical or professional advice. Our articles and the products featured in them are not intended for use as diagnosis, prevention, and/or treatment of health problems for you and/or your pet. It's always best to consult your vet regarding any health issues your pet may have.

Cat wearing a cone (Photo: Adobe Stock)

Cat wearing a cone (Photo: Adobe Stock)

The Nictitating Membrane

Oberon Copeland, Founder And CEO of Very Informed

A cat’s third eyelid is a small, triangular flap of skin that is located in the inner corner of each eye. When the third eyelid is visible, it may look like a small white triangle peeking out from the corner of the eye. The third eyelid is also sometimes called the nictitating membrane or haw. This membrane serves several important functions, including keeping the surface of the eye moist and protected from debris.

In addition, the third eyelid contains a special gland that produces tear film. Cats typically only have their third eyelids visible when they are sick or stressed, as this is when they are most likely to need extra lubrication and protection. If your cat’s third eyelid is constantly visible, it could be a sign of an underlying health problem and you should take them to see a veterinarian.

Sign Of An Underlying Medical Condition

Dr. Sabrina Kong, DVM at WeLoveDoodles

If your cat’s third eyelid (scientifically known as the nictitating membrane) is visible while he is asleep or after being sedated for a medical procedure, you have nothing to worry about. Deep levels of relaxation can cause a cat’s third eyelid to show momentarily, but that’s completely normal; however, if your cat’s third eyelid is visible while he’s awake and alert, there could be an underlying medical condition causing this behavior that you should consult with your trusted vet as soon as possible.

The cause for this could be as simple as something being wrong with the eyelid itself, but it could also mean there’s something wrong with your cat’s eye. He could be suffering from more complex eye conditions such as conjunctivitis (inflammation of the eye membranes), corneal ulcers (damage to the corneas), uveitis (intraocular inflammation), glaucoma (damage to the optic nerve that could lead to blindness), or even Horner’s Syndrome (a neurological disorder caused by a dysfunctioning nerve that affects the eyes and facial muscles).

So with all of that said, if you are constantly seeing your cat’s third eyelid, you should definitely take action on the issue and visit a vet with your kitty immediately.

Cat's third eyelid up close (Photo: Adobe Stock)

Cat’s third eyelid up close (Photo: Adobe Stock)

Extra Layer Of Protection For The Cornea

Dr. Amanda Takiguchi, Veterinarian And Founder of Trending Breeds

Third eyelid is referred to as a nictitating membrane. It’s an extra layer of protection for the cornea. It acts like a windshield wiper against bits of debris. It moistens and protects the eye. It’s usually a hidden eyelid in the inner corner of the first eyelids.

If it is showing just when your cat wakes up or is sleepy, this is fairly normal. If the third eyelid is visible when the cat is fully awake, it can be a sign of illness. It may be caused by an infection, allergies, injury, or an eye irritant.

It could be conjunctivitis, pink eye, worms or another health issue. Cats with conjunctivitis will typically be treated with medicated eye drops or ointment that contain antibiotics and/or steroids. Once treated the third eyelids will retract back into the corner of its first eyelids.

Sign Of Eye Infection

Ginger Burke, Founder Of Elegant Furball

The third eyelid (or nictitating membrane) is a semi-transparent membrane the protect and moisturize the eye while maintaining vision. Several animals have this membrane like birds, lizards and, of course, cats. When functioning normally, the third eyelid will quickly gloss over the cat’s eye and return to being hidden. But sometimes the third eyelid gets stuck over the cat’s eye.

Here are some possible reasons that might happen:

• Conjunctivitis, or eye infection. In addition to the third eyelid, you’ll also notice a lot of swelling around the cat’s eye.

• Dehydration. Cats can hydrate themselves very well. Their kidneys are so efficient that they can hydrate themselves by drinking salt water. If there is an issue with hydration, take your cat to a specialist immediately.

• Blunt trauma. Force and injuries to a cat’s face can cause the third eyelid to show. If you notice this, take your cat to the vet right away.

Other reasons for a visible third eyelid include something stuck in the eye, cancer, Haws syndrome or breed issues (in case of Bermese). Long story short, if you are able to see your cat’s third eyelid, take them to see a specialist as soon as you can. Whatever is causing it is extremely uncomfortable and possibly fatal.

Cat with third eyelid visible in both eyes (Photo: Adobe Stock)

Cat with third eyelid visible in both eyes (Photo: Adobe Stock)

Point To A Gastrointestinal Disease

Courtnye Jackson, Veterinarian And Founder Of The Pets Digest

Most owners notice their cats third eyelid as they are waking up, as this is when they cover the eye and they may also notice them when their cat blinks.

If the third eyelid remains visible it could mean a couple of things, two are

• Ocular Infections or conjunctivitis which is swelling of the conjunctiva. If an owner notices that the third eyelid is visible and there is also some redness of the eye, swelling or ocular discharge they should see their veterinarian.

• Sometimes a visible third eyelid in cats can point to a gastrointestinal disease or disorder such as parasites

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