Cats are masters of disguise. They are very good at hiding any feelings of pain and discomfort. However, there will be some obvious signs if you observe your cat closely.
One tell-tale symptom is when you are able to see your cat’s third eyelid. This normally means that something is ‘off’ with your cat.
But what if your cat is showing its third eyelid without any other symptoms? Such behavior can leave you scratching your head.
In this article, we’ll unravel the enigma of the cat’s third eyelid, diving into its purpose, potential causes for its appearance, and what it could mean for your cat.
Why Do Cats Have A Third Eyelid?
“Scientists believed that humans too had third eyelids many many years ago.”
Take a close look at your cat’s eyes and you will most probably see its upper and lower eyelids.
The third eyelid of your cat are sneakily tucked away at the inner corner of each eye.
This third eyelid is also called the feline nictitating membrane and it acts as a protective shield and ‘windscreen wiper’ for your cat’s eyes
The thin nictitating membrane is able to distribute tears on the cat’s corner to remove dirt, dust and pollen which might obstruct the cat’s vision.
As cats are predators that stalk their prey, they will normally move through tall grass to camouflage their presence.
The third eyelid will be activated to prevent the cat’s eyes from being poked by the grass or injured by its struggling prey.
Scientists believed that humans too had third eyelids many many years ago.
But as we evolved to no longer have the need to hunt for food, our third eyelids have shrunk to become very small.
Should I Be Worried If My Cat’s Third Eyelid Is Showing?
Yes and no.
The general consensus amongst cat owners is that if the cat’s third eyelids are showing, that means that the cat is sick or is in discomfort.
More often than not, that would be the case.
But based on my many years of keeping cats, they will be times when your cat’s third eyelid could be showing without any other worrying symptoms.
We will take a look at both scenarios that can cause the appearance of your cat’s third eyelid.
Deep Sleep
The one very obvious time you can notice your cat’s inner eyelids is during deep sleep. One more thing that cats do well besides self-grooming is sleeping and boy, do cats sleep a lot.
Your cat has sleep phases that are very similar to that in humans. There’s a slow wave sleep phase and rapid eye movement (REM) phase.
The sleep wave sleep phase happens when the cat has settled down and started to snooze.
It is usually called a cat nap when your cat is asleep but still aware of its surroundings.
After about 15 minutes or so, your cat will start to enter deep sleep or rapid eye movement.
This phase is important to help your cat’s body recover and repair itself.
This sleep phase is also called rapid eye movement because your cat’s eyes are bouncing all over the place.
It is possible for your cat to sleep with its eyes partially open with its third eyelids almost fully exposed during deep sleep.
There’s nothing for you to be concerned about as it is a normal occurrence for cats and even dogs too.
Just Woken Up
If your cat’s third eyelids are not showing it is in deep sleep, there’s a high chance that you can notice it when your cat has just woken up or looking sleepy.
8 out of 10 times, I’m able to see my cat’s inner eyelids when he has just woken up from a long nap or deep sleep.
He has this really sleepy look on his face that says “What year is this?”.
As he begrudgingly opens his eyes, his inner eyelids will be showing, almost covering the entire eye. It will slowly start to retract on its own as he gets more awake.
Vaccination
“It largely depends on how sensitive the cat’s body is to the vaccine.”
If your cat has just gotten its vaccination shots from the local vet, its third eyelid can start to show once it’s back home.
The most common types of vaccinations for cats are for:
- Feline Rhinotracheitis Virus/Herpesvirus 1 (FVR/FHV-1)
- Feline Rabies
- Feline Calicivirus (FCV)
- Feline Panleukopenia (FPV)
- Feline Leukaemia (FeLV)
These vaccinations help to protect your cat against many horrible diseases which can be life-threatening and even fatal for young cats.
There are a few common side effects after your cat has been vaccinated.
- Fever
- Vomiting
- Diarrhea
- Lethargy
Some cats will be affected while some won’t. It largely depends on how sensitive the cat’s body is to the vaccine.
Even if your cat doesn’t show any symptoms, its body is still reacting to the vaccine which mimics the virus and stimulates the body to produce antibodies to protect the cat.
On a biological level, the body thinks that the cat is in ill health which causes the cat’s nictitating membrane to show.
Recovering From Sedation
When a cat is sedated, an anesthetic agent is used to knock the cat unconscious and stops the body from relaying any sensations of pain and discomfort to the brain.
Even after the cat has woken up, it will still be feeling very drowsy and sleepy which is a common side effect post sedation.
It is common to see your cat’s third eyelid showing with its eye dilated when it is in this sleepy and drowsy state due to being anesthetized.
Haws Syndrome
Haws syndrome is used to describe the exposure of both third eyelids showing in a cat.
There isn’t one definite cause for Haws syndrome but scientists believe that the cat’s gut condition is usually the culprit.
Cats with Haws syndrome are known to also have diarrhea and other stomach problems like flatulence, bloating or blood in the stools.
Other symptoms will also include loss of appetite and lethargy.
Your cat’s stomach issue could be caused by something as simple as your cat eating spoiled food which resulted in food poisoning.
Or it could be something more serious like intestinal obstruction or parasites.
Intestinal parasites are common in most cats, especially young cats or cats that have never been dewormed before.
These parasites will live and reproduce in your cat’s gastrointestinal tract.
These parasites pose a threat by consuming your cat’s food, leading to malnutrition and weight loss despite normal eating habits.
Cherry Eye
“Although this problem is more common in dogs, it can happen to cats too.”
Some pet owners think that having a cherry eye is the same as their pet having a sore eye. But it is a different medical condition altogether.
Beneath your cat’s third eyelid lies the nictitans gland which is a small pink tissue that produces tears.
The presence of tears doesn’t mean that your cat is capable of crying. The tears are used to clean off any dirt or foreign objects on your cat’s cornea.
Cherry eye is caused when this gland becomes loose and starts to protrude outside the third eyelid.
This can cause the nictitan gland to become swollen and inflamed. which can cause your cat’s third eyelid to show.
Although this problem is more common in dogs, it can happen to cats too.
The best way to solve cherry eye is with surgery to correct the position of the nictitans gland.
Another option is to remove the gland but that will result in another issue called dry eye when there isn’t enough tear production.
Eye Injury Or Infection
Direct injury to your cat’s eye can cause the third eyelid to show.
Your cat can injure its eye by getting into an accident or getting into a fight with another cat or animal. This can cause your cat to puncture or scratch its cornea which can lead to a corneal ulcer.
Your cat can also get an eye infection from foreign objects being stuck in the eye.
Common symptoms of an eye problem include:
- Eye discharge
- Watery eyes
- Cloudy cornea
- Appearance of third eyelid
- Unable to fully open the eyes
- Eye protruding out of the socket
My cat does get an eye infection every now and then. I will clean it will some saline solution for a few days which helps clear it up.
But any eye issue in your cat that doesn’t go away after a few days needs to be checked by the vet.
The vet will be able to prescribe eye drops or antibiotics like penicillin for your cat if there’s a bacterial infection.
Please do not wait to get your cat’s eyes treated. Any damage to your cat’s eye can cause corneal ulcers or loss of sight if left untreated.
It is also best to keep your cat indoors to prevent it from getting into fights and accidents outside.
Horner’s Syndrome
Horner’s syndrome in cats is a neurological disorder that affects your cat’s facial muscles and the appearance of the eyes.
This medical condition is caused by damaged nerves that lead to the cat’s face that can be brought about by a neck injury, tumors, ear infection, spinal injury and neurological disorders.
Symptoms include:
- Droppy upper eyelids
- Eyes are sunken in
- Protrusion of the third eyelid
- Cross-eyed
If Horner’s syndrome is caused by an infection or injury, your cat will require medication or surgery to recover.
In many cases, the vet will ask you to just observe your cat as this problem can clear up and go away on its own over time.
Glaucoma
Glaucoma is a serious eye condition that results from an increase in pressure in your cat’s eye.
Pressure within the eye, also known as intraocular pressure (IOP), is essential for maintaining the shape of the eye and enabling it to function properly.
But when the pressure gets too high, it can damage the optic nerve and cause blindness in cats.
Symptoms of glaucoma in cats include:
- Pain in the eye
- Redness and inflammation
- Cloudy cornea
- Loss of vision
- Third eyelid showing
The increased intraocular pressure can cause the third eyelid to become more visible or partially cover the eye.
This may be due to the cat’s attempt to protect the eye from further irritation or pain,
Glaucoma is a serious eye problem and needs immediate medical attention or your cat might go permanently blind.