Health problems that cause the third eyelid in cats

Cats are fascinating creatures in many ways. They have highly developed senses and see the world as no one does. Feline eyes are unique, not only to each breed, but also to each cat. They come in different shapes, colors, and sizes. Some may even have heterochromia (two different colored eyes).

But the only thing cats have in common is their third eyelid . This is known as the third eye or inner eyelid .

Like us, cats have two visible eyelids. One of them is located in the upper part of the eye and the other, in the lower part. However, what humans do not have is the third eyelid, a retractable and usually hidden eyelid, which is located in the inner corner of the cat’s eyes, near the nose.

Below I explain what it consists of and the health problems that its presence can indicate.

What is the third eyelid in cats?

The third eyelid is known as the nictitating membrane.  This membrane, found in the inner corner of the eye, is an additional layer of protection for the cornea and also serves to keep the eye moist while maintaining vision.

The third can be likened to “a windshield wiper blade” by removing debris and pollen from the surface and redistributing tears onto the cornea. It retracts towards the inner corner of each eye. (which makes it somewhat disorienting to human observers).

Both cats and dogs have a third eyelid . Also birds, reptiles, amphibians, fish and some other mammals.

Your cat’s third eyelid acts as a shield for her cornea as she moves through tall grass and during skirmishes with neighborhood felines or tough prey.

Instead, this membrane sometimes unfolds and can cover the eye. This prolapse of the gland  indicates a health complication.


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What the third eyelid is trying to tell you

Other than those brief moments when your cat wakes up from sleep, you shouldn’t see the nictitating membrane. If your cat’s third eyelid appears in one or both eyes, take him to the vet to make sure he is not suffering from one of the following health problems:

Trauma and injuries

Most traumatic eye injuries are due to fighting, foreign objects in the eyes, or similar circumstances.

Your cat can get a corneal ulcer if there is a scratch on the transparent surface of the eye. The third eyelid will prolapse due to this type of trauma.

Cat dehydration

The third eyelid sometimes occurs if a cat is severely dehydrated or is experiencing weight loss due to another health problem. The cats with glaucoma may also show the third eyelid.

Eye infections

The nictitating membrane may also occur as a symptom of virus feline upper airway or conjunctivitis.

Your cat’s third eyelid is a perfectly normal part of her anatomy, until it becomes obvious. When in doubt, check with your vet.

Haw syndrome

In this case, the nictitating membrane appears in both eyes. Its appearance is related to some type of gastrointestinal upset, intestinal worms or other parasites, food intolerance, a viral or bacterial intestinal infection.

This condition often clears up suddenly within 3 to 4 weeks.

Strange body

Any object, dirt, dust, among other elements that may have remained in the cat’s eyes , will cause this membrane to appear, to prevent it from entering the eyeball further.

Horner syndrome

It is a neurological disease that arises from dysfunction of the sympathetic nerves of the eye. The sympathetic nervous system controls many glandular and involuntary functions of the body. Third eyelid prolapse is one of the four clinical signs that develop with Horner syndrome. This syndrome usually affects only one eye at a time.


They can be melanomas, leukemia, or squamous cell carcinomas that appear on the eyelids and expand. The most common of these tumors is adenocarcinoma that affects the gland of the third eyelid.


Your cat may have a visible third eyelid due to her  genetic heritage . Breeds like the Burmese often have this trait.


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Third eyelid treatment

There is no definitive treatment for the appearance of the third eyelid, since there is not a single health problem that causes its appearance. However, there are a few things you can do if  your cat’s third eyelid is showing :

  • Clean the area. Gently wipe the eye area with wet cat wipes. Use warm water, a soft cloth, and a pet-safe antibacterial solution if you can’t find cat wipes at this time.
  • When it comes to dehydration. It is extremely important for your cat to have a good fluid intake. Provide canned foods that are high in moisture, and make sure your pet has constant access to clean, fresh water.
  • Protect your home against stress. Try to make your house or apartment as quiet and relaxing as possible for the cat. Respiratory infections and other health conditions get worse when the cat is stressed. Advise children and guests of the house to be quiet and not to disturb the cat physically or emotionally.
  • The syndrome Hawdisappear only when the intestinal and digestive problems that have caused the membrane finished.
  • In the case of conjunctivitis in cats, wounds, foreign bodies in the eye, eye drops and other medications may be administered, and in the case of tumors, surgical intervention and radiotherapy may be carried out.

If your vet has prescribed any medications and given you care advice, be sure to follow everything strictly. Negligence on your behalf can and will only make the problem worse.



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