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Home > Cats > How Many Eyelids Do Cats Have? Cat Eye Anatomy Explained

How Many Eyelids Do Cats Have? Cat Eye Anatomy Explained

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Cats are truly peculiar creatures. From their curious habits to their unique anatomy, they are an enigma. One surprising aspect of cats is that they have more eyelids than humans!

You’ve probably noticed that when your cat squints its eye, a membrane slides across its eyes, somewhat like a curtain. What you’ve just noticed is the cat’s third eyelid. That’s right; unlike humans, cats have one extra eyelid besides the upper and lower eyelids.

So, what role does this extra eyelid play, and is it even necessary? Keep reading for answers to these and more questions about your cat’s eyelids.

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The Anatomy of a Cat’s Eye

Dilute Tortoiseshell cat with yellow eyes
Image Credit: Mary Swift, Shutterstock

Cats’ eyes are quite different from ours, and they don’t see the world the same way we do. Right off the bat, you’ll notice cats have much larger, differently shaped pupils that dilate in low light and narrow down when there’s plenty of light.

The cat’s eye colors are also quite distinct from ours, ranging from dark yellow to green, compared to our white eyeballs. Cat’s eyes also glow in the dark because of the tapetum lucidum, a layer of reflective cells that captures any incoming light and reflects it back onto their photoreceptors. This allows cats to see better in the dark than humans.

Now back to the eyelids. Cats have three eyelids: the upper eyelid, the lower eyelid, and the third eyelid. The upper and lower eyelids are the eyelids we are most familiar with, and they open and close to blink. The third eyelid is also known as the nictitating membrane or the haw, and it’s located in the inner corner of their eyes.

The Role of the Third Eyelid

So what’s this extra eyelid for? Well, the third eyelid is a protective membrane that helps to keep the eye moist, free of debris and dust, and lubricated. It also helps cats’ eyes to focus better on things in their field of vision. In some cases, it can even help them see prey or predators quickly in dim light.

The third eyelid also serves as an indicator of your cat’s health and is a good way to tell if they are feeling healthy or not. If the eyelid is always visible, it could mean that your cat isn’t feeling well. This can be due to eye infections, dryness, trauma, or other conditions.

Why Can’t I See My Cat’s Third Eyelid?

close up of a gray cat with yellow eyes
Image By: shraga kopstein, Unsplash

Why can’t we see our cat’s third eyelid? Well, it’s because cats’ eyelids are usually positioned in such a way that the third eyelid isn’t exposed. When the cat blinks or squints, you may be able to catch glimpses of it if you look closely.

But don’t go trying to pull your cat’s eyelids open. It’s important to be very gentle and never pull or tug a cat’s eyelids, as this can cause injury or even infection. You may even accidentally poke the cat’s eye with your finger or get a nasty scratch if you haven’t declawed your cat.

The third eyelid is completely out of bounds since it’s a very sensitive area, and any manipulation can cause serious problems. So instead of trying to pull the eyelids open, just observe your cat’s eyes and try to sneak a glimpse of its third eyelid.

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Should You Be Worried If Your Cat’s Third Eyelid Is Showing?

If you notice your cat’s third eyelid is showing for extended periods of time, it could indicate an underlying health issue. We recommend taking your cat to the vet as soon as possible to get them checked out and treated.

What Illnesses Could Cause a Protruding Third Eyelid?

There are quite a few illnesses that can cause a protruding third eyelid in your cat’s eye. Here are some common illnesses characterized by a protruding third eyelid.

Conjunctivitis

cat with conjuctivitis
Image By: KAY4YK, Shutterstock

Conjunctivitis is an inflammation of the eyelid and conjunctiva (the thin, protective membrane that covers the whites of your cat’s eyes). It can be caused by allergies, viruses, or bacterial infections.

Common symptoms of conjunctivitis include red and watery eyes, excessive blinking, eyelid swelling, and a protruding third eyelid. If you notice any of these symptoms in your cat, rush it to the nearest vet for a proper diagnosis and treatment.

Keratoconjunctivitis Sicca

This is an inflammation of the eyelids and conjunctiva due to insufficient tear production. It can lead to dry eyes, redness, swelling of the eyelids, eyelid discharge, and an ever-present third eyelid.

KCS can be treated with medications or sometimes even with artificial tears if needed. Just be sure to consult with your vet before administering any kind of medication.

Blunt Force Trauma or Injury

close up kitten with eyes infection
Image By: RJ22, Shutterstock

If your cat is unfortunate enough to experience blunt force trauma or injury, it can cause the eyelids to protrude. This could be due to swelling, infection, irritation of the eyelid membrane, or even an abrasion between the eyelid and eyeball.

In any case, it’s important to seek medical attention right away if you suspect that your cat has experienced an injury near its eyes. The earlier you do so, the better the chances of your cat making a full recovery.

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Cat Eyes: Final Thoughts

Cats have three eyelids, the upper and lower eyelids, and the third eyelid. All of them help keep their eyes healthy and functioning properly. If you notice that your cat’s third eyelid is often visible, it may be a sign of an underlying issue, so make sure to take them to the vet for a proper diagnosis and treatment plan.

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Featured Image Credit: Jumpstory

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