The third eyelid is also known as the nictitating membrane. Humans do not have a third eyelid, but cats and many other animals do. Its role is to protect the eye's outer layer and keep it moist.
Most of the time, it is not visible, as it retracts into the inner corner of the eye. But it becomes visible when your cat is unwell or has a problem with their eye. This is an indication that you should take your cat to the vet.
What does a cat's third eyelid look like?
A normal third eyelid is not easily visible. Yet you might occasionally notice it when your cat blinks, yawns or wakes up from a deep sleep.
A third eyelid is a conical-shaped film in the inner corner of your cat’s eyes. It is very thin and usually has a dark rim around it. The most inner part is usually a very pale pink or white colour. If it is red, this is abnormal.
What do you do when your cat's third eyelid is showing?
If your cat’s third eyelid shows, you should take them to a veterinarian for a check-over. Primary eye conditions, particularly trauma, can progress quickly and can cause serious consequences if left untreated. If your cat doesn’t have a primary eye condition, they will also need treatment for the condition that makes him feel unwell.
Why does my cat have a third eyelid visible in one eye only?
If your cat only has one of their third eyelids showing, it usually indicates that the problem is with that specific eye, rather than general ill-health.
Trauma to the eye, such as an object, a scratch, a corneal ulcer, or a foreign body in the eye, can cause this. It could also be an infection that has not yet infected the other eye.
Eye injury is serious, so it is important that you take your cat to the veterinarian for investigation. Eye conditions are painful and can be serious. If left untreated, they can rapidly lead to vision problems or even blindness.
Why are my cat's third eyelids visible in both eyes?
If your cat’s eyes both show their third eyelids, this indicates that either there is a problem with both eyes or your cat is generally feeling unwell. Eye infections, such as conjunctivitis (also called pink eye), tend to affect both eyes simultaneously. Internal eye problems, such as glaucoma, can also cause the third eyelids to protrude.
Having said that, it may not be a problem with the eyes. Any ill-health that causes a fever and general malaise can result in the third eyelids protruding. This is particularly common for cat flu infections.
Why are my cat's eyelids red?
If your cat’s inner eyelids (conjunctiva) are red, this means they are inflamed and sore. This is known as conjunctivitis. Conjunctivitis is usually caused by a bacterial or viral infection, but trauma can also trigger it and require treatment by a veterinarian.
Can you see a cat's inner eyelid?
In a normal cat, you will struggle to see the third eyelid. You might see it protract slightly when your cat blinks, yawns or when they first wake up. Straight after, it should return to the normal position in the inner corner of the eye.
Why is my cat's third eyelid showing and they have diarrhoea?
The third eyelid can show due to any feeling of ill health. However, a condition known as Haw’s Syndrome can cause diarrhoea and third eyelid protrusion in cats. Much is unknown about it, but it has been speculatively suggested that it is associated with either tapeworm or intestinal viral infections in young cats. Most of the time, it is mild, and cats recover with supportive treatment from their veterinarian over the course of several weeks.
Why is my cat's third eyelid showing and they are lethargic?
When your cat is unwell, its third eyelids may protrude, and it may act lethargic. It is unknown why the third eyelids protrude, but it is thought to be because there is a dysfunction in the nerves that tell the third eyelids to stay in place. If your cat is lethargic and has protruding third eyelids, you should take it to the vet, as there are many potential causes that need treatment.
Why is my cat's third eyelid showing and they are sneezing?
Upper respiratory tract infections can cause third-eyelid protrusion and sneezing. These infections can be part of the ‘cat flu’ complex. You should take your cat to the vet, if they are showing these signs, as cat flu can have serious consequences if left untreated, both in the short-term and over your cat's lifetime.
Why is my cat's third eyelid showing, but they're showing no other symptoms?
There are many reasons why your cat’s third eyelids might be showing, even when you do not notice other symptoms. If your cat has just woken up from a deep sleep, wait some time to see if the third eyelids retract. Yet if they stay visible, your cat needs a visit to a veterinarian to investigate why the eyelids are protruding. There may be a corneal abrasion, an underlying health condition or an eye condition that needs to be treated.
Is my cat's third eyelid due to stress?
Stress does not cause the third eyelid to protrude. What may have happened is that cat flu can be caused by viruses that stay latent in the body.
At times of stress, the virus becomes active again and causes ill health and third eyelid protrusion. Therefore, if your cat has had an episode of cat flu before, you should try to keep its environment as stress-free as possible by using pheromone diffusers and making a conscious effort not to make drastic changes to its living environment.
Why is my cat's third eyelid swollen?
If your cat’s third eyelid protrudes and seems swollen, this might be a condition known as cherry eye. Cherry eye is more common in dogs than cats, yet certain breeds, such as the Burmese, are prone to it.
A gland in the third eyelid swells when it becomes swollen, turning the third eyelid inside out, which interferes with its function. Medical management with eye drops is rarely successful, and most cases need to be surgically repositioned.
Why is my cat's inner eyelid stuck?
If your cat’s third (inner) eyelid is stuck in an outward position, this means that there is something wrong with your cat. Your cat might be feeling unwell, or they might have a primary problem with the eye. There are many causes, and you should visit a veterinarian for your cat to have a checkover.
When should I see a vet?
If your cat’s third eyelid in one or both eyes is visible and doesn’t return to its normal position, it must be clinically examined by a veterinarian. They may need treatment for the eye or for ill health. There are many causes of visible third eyelids; if left untreated, many of them can have serious consequences.
