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How Many Eyelids Do Cats Have? Do They Have More Than One?

Cats are one of the most popular pets in the world. They are known for their adorable faces, soft fur, and above all else—their hypnotic eyes. But do you know how many eyelids cats have? Contrary to popular belief, most cats do not have two eyelids per eye as humans do.

The vast majority of cats actually have six eyelids—an upper lid, a lower lid, and a third lid located in the corner of each eye called the nictitating membrane or “haw”. This is a thin, translucent layer of tissue that can be drawn across the eye to protect it from debris and foreign objects. Although most cats have this third eyelid, there are some breeds of cats that may only have two eyelids per eye, for example, the Siamese. Three plus three means cats have six eyelids in total. Read on to find out all about their unique ocular anatomy.

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How Do Cats Blink?

The lower and upper eyelids of felines work together to cover and protect their eyes. In cats, both upper and lower eyelids move toward each other when they blink. Although they move toward each other, they typically don’t completely close together as ours do. If anything, the cat may appear as if they are squinting. The third eyelid, the nictitating membrane, moves diagonally across the eye and helps to keep the surface of the eye lubricated and clean.

Green eyes
Image Credit: M_Light, Shutterstock

How Do I Find My Cat’s Third Eyelid?

Many cat owners have never seen their cat’s third eyelid and are not sure where to look for it. The third eyelid is a thin membrane that is located on the inside corner of your cat’s eye. It is usually only visible when your cat’s eyes are open wide. You can check for the third eyelid by looking at the white part of your cat’s eye. If you see a small, pink or light red triangle-shaped membrane, then your cat has a third eyelid.

What Color Should My Cat’s Third Eyelid Be?

​​The third eyelid is a membrane that is visible in cats and dogs. It is located in the inner corner of the eye and is normally hidden by the upper and lower eyelids. The color of the third eyelid can vary depending on the animal’s breed, age, and health. In healthy cats, the third eyelid should be pink or light red. If the third eyelid is darker than normal, it may be a sign of illness or injury.

cat's eye close up_Pixabay
Image Credit: Pixabay

Why Is My Cat’s Third Eyelid Dark?

There are a few different reasons why a cat’s third eyelid may be dark. One possibility is that the cat has a scratch on the cornea, which would cause the area to become inflamed and discolored. Another potential explanation is that the cat has an infection or other medical condition that is causing the eye to discharge pus or other fluids. Other causes could include a tumor, a foreign body in the eye, or high blood pressure. Additionally, melanin pigmentation may cause the third eyelid to appear darker than normal, especially in black cats. In this case, the darker color is totally harmless.

What Does A Cat’s Third Eyelid Do?

A cat’s third eyelid is called a nictitating membrane. This membrane contains special glands that facilitate tear production. In the inside corner of the eye, under the upper and lower eyelids, sits a light red or pink membrane. It is very thin and moves very quickly. In response to a cat’s blinking, the nictitating membrane travels diagonally across the eye very rapidly. It’s difficult to catch the membrane moving. Instead, your cat may simply appear to be squinting. Each of these three eyelids protects the eyes of your cat.

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Credit: Mary Swift, Shutterstock

What Is the Purpose of The Third Eyelid In Blinking For Cats?

The purpose of cats’ blinking differs from that of humans. When we blink, we spread tears across the eye surface to keep it moist and remove debris. However, cats don’t blink tears away. After the nictating membrane removes debris, their tears evaporate. By doing this, cats are able to get the benefits of blinking without ever closing their eyes completely.

How Else Does The Third Eyelid Protect A Cat’s Eyes?

Cats use their third eyelid, or nictitating membrane, when hunting. This extra eyelid acts as a windshield wiper to keep the cat’s eyes clean and clear. In addition, the third eyelid of cats can also extend upward in order to protect the eyeball from injury. For example, when a cat moves through tall grass or when a cat is closing in on their prey, the cat’s third eyelid will elevate to ensure that nothing can scratch their cornea.

a maine coon cat hunting a mouse outdoor
Image Credit: greg.visuals, Shutterstock

Why Is My Cat’s Third Eyelid So Thin?

The third eyelid is so thin it is almost translucent. Cats can probably at least see light and dark if not make out some shapes through the nictitating membrane. Some theories suggest that cats have an advantage when hunting prey because they can see through the membrane of this eyelid.

Why Does My Cat’s Eye Look Weird?

There are a couple of things that could be going on with your cat’s eye if it looks weird. One possibility is that your cat has a condition called uveitis, which is inflammation of the uvea, the middle layer of the eye. This can cause the pupil to look cloudy or swollen. Another possibility is that your cat has a cataract, which is a clouding of the lens in the eye that can lead to vision problems. For issues affecting your cat’s third eyelid, read the next section.

tabby cat big eyes closeup
Image Credit: Real Moment, Shutterstock

Why Is My Cat’s Third Eyelid Showing?

There are times when eye injuries are accompanied by the protrusion of the third eyelid. The third eyelid in felines protects the cornea, and it is normally not visible. In cases of injury or illness to the eye, the third eyelid can protrude or appear swollen. Contact your veterinarian as soon as possible if you see your cat’s third eyelid sticking out.

Often, seeing the nictitating membrane is a sign that there is a foreign body in the eye or a scratch. Plant fragments, sticks, excess pollen, or other debris could be causing irritation to your cat’s eyes. Your vet will check the eye for scratches or ulcerations if the third eyelid is sticking out. An untreated injury could lead to further infection.

What Is Haw’s Syndrome In Cats?

Haw’s syndrome is pretty common in cats. This is a condition in which both third eyelids protrude (or prolapse). In cats, the third eyelid can protrude for a variety of reasons. If both eyelids prolapse at the same time that your cat is experiencing diarrhea or other gut troubles, their illness is labeled Haw’s syndrome. It’s not known exactly what causes Haw’s syndrome, but your cat’s diarrhea might most commonly be linked to tapeworm infestation or viral infection. Sometimes, other cats in your household will also get Haw’s syndrome at the same time. If your cat is dull, depressed, and has no appetite, your veterinarian will perform a more comprehensive exam to rule out other causes of diarrhea and protruding third eyelids.

cat examined by Vets
Image Credit: Kzenon, Shutterstock

How Long Does Haw’s Syndrome Last & How Is It Treated?

Usually, Haw’s syndrome is self-limiting, meaning it goes away without treatment after four to six weeks. In most cases, cats recover from this condition on their own, but if protrusion of the third eyelid persists for more than four months, your vet may reconsider their diagnosis.

If a cause of diarrhea can be identified, it will be treated specifically, generally with dietary changes or deworming tablets. Usually, it’s not necessary to form a treatment plan for your cat’s eyes. However, if the third eyelid has moved out to cover the majority of the surface of the eye, your vet may prescribe 2.5% phenylephrine eye drops. These can temporarily fix the protrusion, but they will have no impact on the gastrointestinal issues driving the syndrome’s duration.

What Age Cats Are Affected By Haw’s Syndrome?

The occurrence of Haw’s syndrome is not age-dependent; however, young adult felines are more likely to suffer from this disease than older cats.

siamese kitten with blue eyes
Image Credit: Alla Vanahs, Shutterstock

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In conclusion, cats have a total of six eyelids. The upper and lower eyelids help to protect their eyes from dirt, dust, and other particles. The third eyelid, or nictitating membrane, helps to keep the eye lubricated and healthy. While this third eyelid may seem like a small detail, it is actually essential to their vision and overall health. So the next time you see your cat blinking lazily in the sun, remember that they are doing something much more complex than you may think!

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Featured Image Credit: Anna Azarenko, Shutterstock