Third Eyelid Showing in Cats - Causes and Treatment

By Josie F. Turner, Journalist specialized in Animal Welfare. Updated: October 16, 2018
Third Eyelid Showing in Cats - Causes and Treatment

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Cats' eyes can be truly fascinating for those who take their time to look into them. Not only due to the fabulous combinations of colors, but also due to the unusual behavior of their pupils, which change in size depending on the amount of light in the environment. Their eyes are so well known for their distinctive appearance, reflection spots on roads are known as cat's eyes.

A cat's eye contains an inner membrane known as the third eyelid. This is to differentiate it from the outer eyelids. You may have never seen it, as doing so is a sign of a health problem. As such, if you've recently noticed it, you will need to read up on the causes and treatment for a third eyelid showing in cats. Fortunately, AnimalWised provides the information to do so. It is a symptom of a heath problem in your cat and should not be ignored under any circumstances.

You may also be interested in: Gingivitis in Cats: Causes and Treatment

What is the third eyelid?

The scientific name of this membrane located in the eyes of most mammals, including cats, is Tertia palpebra. More commonly it is known as the third eyelid or nictitating membrane. It is a tissue located around the cornea, conjunctiva and mucous membrane. Although it isn't commonly spotted, you might notice some secretions between the eye and the outer eyelids when your cat is half asleep. As they wake up, a cat's third eyelid showing as they begin to open their eyes is normal. However, it should not be visible once open, awake and alert.

The role of the third eyelid is to protect the eyeballs from any foreign object and from traumas as a result of a hit or knock. It is also responsible for releasing a liquid, whose antiseptic properties are capable of fighting against the presence of bacteria and microorganisms that could cause disease. However, these protective uses of the third eyelid should not lead to the feline nictitating membrane to show all the time.

Nictitating membranes are also sometimes known as a 'haw'. In other animals, including many birds, it can be used to moisten the eyeball while open. As it is transparent or translucent, it means the animal can still see. Some mammals have a full third eyelid which can do this, but the cat does not. It is believed that some species have evolved away from using this membrane. Even humans have a vestigial part of their conjunctiva known as the plica semilunaris which is thought to have once been a third eyelid.

If you see that your cat's third eyelid is visible, either in one eyeball or in both, this means that they are in pain or suffering from a condition or disease[1]. Some research suggests that the appearance of this membrane is related to intestinal parasites and digestive problems, whereas others state that if this membrane is visible then the problem is related to the eye itself. In these latter cases, the problem with the cat's inner eyelid could be due to a prolapse[2]. In order for you to have all the information, we will show you the causes that can cause this tissue to appear in your cat's eye.

Third Eyelid Showing in Cats - Causes and Treatment - What is the third eyelid?

Causes of third eyelid showing in cats

If you see that your cat's nictitating membrane is visible in one or both eyes, it is usually a symptom of a secondary problem. These are some of the root causes of third eyelid showing in cats:

  • Conjunctivitis: this ocular infection doesn't only cause the appearance of the third eyelid, but is also causes swelling, tearing and lacrimation.
  • Dehydration: when the cat is suffering from a severe lack of water, the appearance of this ocular tissue is a sign and symptom of a serious health condition. It will need to be treated by a specialist.
  • Wounds: if your cat has suffered a blow or trauma to the face, both of its eyes may have become affected. Take them to the vet straight away.
  • Foreign body: anything that gets into the cat's eyes, whether rubbish, dust or something else will cause this membrane to appear, as it is a mechanism to prevent it from further imbedding into the eyeball.
  • Cancer: it's possible for this small organ to be affected by the formation of cancer cells. Fortunately, the disease is relatively rare in this part of the eye. Unfortunately, if it does occur, then it can progress quickly and become fatal[3].
  • Haw's syndrome: this name is given to the appearance of the third eyelid when related to an intestinal problem that the cat is suffering from, or has suffered from recently, whether intense diarrhea or the presence of parasites. With Haw's syndrome in cats, the third eyelid turns into a protrusion thanks to prolapse. it most commonly occurs in cats less than 2 years of age. Prolapse of the nictitating membrane is one of the most common issues with third eyelids in dogs[4].
  • Genetics: some cat breeds, such as the Burmese, might be prone to suffering a rupture or protrusion of this membrane inside the eye, which is very uncomfortable for them.
  • Dermoid cyst: a dermoid cyst is one which is present at birth and can grow slowly as they age. It is usually not observed until secondary symptoms occur. One case study on a kitten with third eye showing from 2016 shows that it can be present on any part of the eye. The result is still protrusion of the nictitating membrane[5]. However, the same study notes that any ocular dermoid occurs infrequently and can respond well to treatment.

Furthermore, if you see the third eyelid in your cat it is also highly likely that its eyes will start to lacrimate. They will probably try to touch them with their paws owing to the discomfort caused when this membrane is out of place.

Third eyelid showing in one eye

As a note, if a cat's inner eyelid is showing in one eye and not the other, it is still a cause for concern. It may imply a problem on one side of the body, but it still means there is an issue which needs resolving. It might be that you see a cat's third eyelid showing in one eye which progresses to both. This implies the progression of one of the causes listed above.

If a cat third eyelid showing in one eye is observed, it could be some direct damage to this membrane. This would explain why it is visible in one eye and not the other. It could be a piece of dust which has lodged within or even something hitting it. As we have stated above, cancer is a possible cause of protrusion in the third eyelid, but this is relatively rare. Regardless if a cat's nictitating membrane is observed in one eye or two, you should take them to the vet for evaluation.

Third Eyelid Showing in Cats - Causes and Treatment - Third eyelid showing in one eye

Treatment for a third eyelid showing in cats

Owing to the various reasons that can cause the cat's nictitating membrane to occupy more space in the eye than it should, there are several types of treatment. This treatment depends on the source of the problem.

In the case of dehydration causing your cat's third eyelid showing, you should give the cat plenty of wet food and water in order to halt the process. It is also recommended to take the cat to the vet, as the animal has been lacking water for too long to be treated at home. Many treatments for a third eye protrusion

In the case of conjunctivitis, wounds, foreign bodies in the eye and cancer, only the vet's diagnosis will be able to determine the next step to follow. They might be prescribed eye drops and other medications in the first 3 problems, depending on the severity. If they have cancer they may be recommended surgery and/or radiotherapy. Surgical removal may occur if there is a benign tumor on the cat's inner eyelid. Only the specialist can decide on the best option to conserve the cat's health and quality of life. As the cat recovers, their inner eyelid should start to retract.

Haws syndrome should disappear by itself, once the intestinal and digestive problems that caused the appearance of the membrane go away. This, in turn, will lead to the nictitating membrane gradually disappearing as the cat returns to health.

When a genetic reason is behind it, the vet will use medical studies to determine whether the cat's inner eyelid membrane is affecting the cat's vision and causing discomfort. If this is the case the vet may also resort to surgery. This process will not to extract their third eyelid, but will put the feline nictitating membrane back into its correct position. If there are any other infections or conditions causing a cat's third eyelid to show, they will be treated accordingly.

If you want to read similar articles to Third Eyelid Showing in Cats - Causes and Treatment, we recommend you visit our Eye care category.


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Please help. My cat has had third eyelid showing for 5 days. Taken to vets and initially was due to bad allergies (which are cleared now) but the eyelids are still showing and seem to be getting worse. They are almost covering entire eye. We are giving him eyedrops (vet subscribed) but no impact. We have also been back to the vet twice (different vet 3rd time) and they have given him the all clear for other health conditions that could be causing it. Am I being impatient? Should the eyelids be back to normal by now?
Administrador AnimalWised
Hi Gen,

If your cat's third eyelid is showing, they will need a physical examination by a veterinary medical health professional. Since you have been to the vet 3 times and have had a second opinion, then this will imply you will need to wait for the symptoms to go down. However, this is only a suggestion, it is possible these vets have missed something, but we would think it unlikely. Keep an eye on related symptoms and if they seem to be getting worse in general then the only thing you can do is take them to the vet.
Diane Baker
Thanks again for your interest and best wishes. To be honest we are not exactly good off, we just make sure if we take on a pet it becomes family and all family deserves the best of treatment we can afford. It does set us back, but we are great ful we do have the means to give them the care they get. All animals are so loving uncondionally and they deserve the same in return. Best of wishes to you for all your good works and to all your other readers that feel confident in your opinions.
Administrador AnimalWised
Thanks again Diane,

Your words are very kind and we are glad your cat gets to share in this kindness. We hope to hear back with an update soon.
Diane Baker
I would like to thank you for your interest, words and caringness about my kitty Princess. I just spoke to the vets office and after many tears felt I would like to let you know the outcome as you asked. I was told they felt it best not to try to separate the third eye, but they believe she no longer has vision in that eye and would like to send us to an eye vet, now, to see if it should be removed and to see if it is cancer. I asked what the blood work showed and they said none was taken, still. Which I do not understand. I do not know if I will go with his recommendation or pick one of my own. Like you said I have friends at the cat network who may be able to recommend someone they have used. It has confirmed one thing in my mind if nothing else. From now on if any of our cats have a specific problem, then that is the vet I will send them to. Eye doctors for eye problems, pulmonary doctor for lung problems, etc. I have spend many years working for a general practice attorney and just like him, if it were a case that need special attention in an area we would refer him, as he was trained in all area of laws but specialized in none. I believe our pets deserve no less than the care we get or provide for our other family members, so for me no more messing round with someone who does not even think todo blood work. As that is the first thing my doctors due with me, especially if they are unsure of any issue I hope it does come down to removing her eye, but if it is cancer and could spread that is what we will do. It is not like we have a great deal of money and this has already been very costly but we decided when we rescued exact cat that we would always make sure they got the best of care possible and nothing short of what we would ourselves. As of lately, I think they have gotten better than I have allowed myself. But at times you have to decide depending on the most in need. I had a neighbor whose cat passed and she could not afford to have him cremated, so we paid the 200.00 for him to have private cremation and it made a big difference in how she dealt with her loss. I try to always caution those who love cats and want to save them all. They are not really doing right by a pet If they cannot afford to feed it, care for it and take it to the vet as it should be, I am very, very great ful that we are in a position at this time to make sure princess gets the care she needs. Thank you again for your interest and for all you do to help others as well. D
Administrador AnimalWised
Hi Diane,

We are so sorry to hear the bad news. But we do hope that now treatment has been started, they will be able to get the care there need. We also know how difficult expenses can be. Even with people who are doing well financially when they get a cat, circumstances can change. All the best and get in touch any time.
Diane Baker
Thank you for the advice on our cat, you hit the nail on the head when you stated I have lost faith in him. However, my roommate still holds him in high regards, so it causes conflict when I suggest another opinion. I said we lost two pets prior, one was from kidney disease, I was foolish enough to leave my cat at the vets for almost a week. That was my fault, but I see no point why I did as no one is there when it is closed. My vet personally is a nice person, but this was my cat that was closest to me. He said it was not painful and gave him nothing for it, which when I later read articles on it (too late) it said it was very painful. He was kind enough to let me meet the young helpers that would go into to feed the pets, and the last night my pet vomited after being feed through a tub, and they would not call the vet, they said they would make a note of it and then rushed me out of there so they could leave. I felt awful, the next day I took the cats cage with me as I was bringing him home. After he was feed through the tub he went into a type of convulsion and they gave him oxygen and since they just put a dog to sleep to fix him, said they would go right back to my cat when they were done. I went outside to give them privacy at the promise they would get me before going back and taking my cats tube out. After constantly asking if they were ready, I walked towards the back as my vet was walking out to tell me my cat has passed. I was both heart broken and mad. He did apologize and admit he had dropped the ball on not getting me as they promised. I never forgave myself. And our other cat who had was a diabetic and overweight, would constantly have her skin ripping apart, it looked awful. We were having construction done on our home and it seemed whenever it was normal she would heal fine and then first day the workers came back she would have three to four tears in her skin through all the layers, all I could see was red from her insides. Again our vet said it was not painful so nothing for pain and said it was from being a diabetic only this time I could not accept that and made an appointment with a specialist who for one said it was painful, and two it was more from stress not being a diabetic, unfortunately she died on the table, her heart gave out, I guess she had suffered enough. So yes, I have lost faith in this vet, even though he was very kind to me when my first cat was sick and even came in on a Saturday so I could visit with my cat. But by the time the day came he passed, he had he back to me and was sleeping in the litter box when I went in and had not interest in seeing me anymore. I feel I left him down when he needed me the most. I should of just taken him home with me and let him pass here and made sure he did not suffer. So although some have had a great experience with this vet. there are a few who have not. And I mention no names as I do not like to talk ill of others. So I thank you for your advice, it was very professional and tells me I need to follow my heart and my gut in the end. After a disagreement with my roommate she said I could get a specialist but like you said I am going to try to be objective and she does not seem to be in pain so I just said we will leave things as they are and will drop her off for her procedure on Thursday. I was going to stay and wait as I always have even when the just were fixed but that place makes me too sad now and I do not wish to be there. Again, this is not reflection on this vet as a person, I just have my own opinion due to my own experiences. Thank you for your interest, and I am happy to say her third eye is starting to disappear a small area in one corner. I guess it is up to my higher power in the end. Thanks again.
Administrador AnimalWised
Hi Diane,

It sounds like you may have also needed to talk it out, so we're glad you addressed it with your roommate and had the chance to speak about it properly. Procedures like these are always difficult and they prey on our worries. We hope the worry is unfounded and everything goes well. Good luck and let us know how it goes.
Diane Baker
On Wednesday, 5 days ago, we noticed our one cats third eyelid had completely covered her one eye (until this I had never heard of a third eye) we took her to our vet (whom I have lost faith in over a few events over the years but my roommate still likes him) he said it was stuck and gave her a shot of antibiotics and drops of the same for us to give her up until This coming Thursday. He said he needs to put her in a twilight sleep to separate it to see what is wrong with her eye. He said it could be a scratch, her cornia could have a hole in it, or it could be a sign of a respiratory problem. I asked about drops for pain and he claims it is not painful, but he seems to say that in any situation (from past experiences). I am just wondering on you opinion on this. Should we get a eye specialist for her or let him do the procedure as planned. She is hiding right now so I cannot get a picture, but her eye has turned pinker than before. She is a very good cat and is very sensitive and allows the drops. She even purred he entire time we had her at the vets. I just want to make sure we are getting her the best care. We belong to the cat network, do volunteer work for them and orginally had 7 cats whom were all rescued. We now have 5. I will send a picture when we find her for her next dose of eye drops but was just wondering if you had any special advice and let me know for one, could it be painful and two could it be related to a respiratory problem?
Administrador AnimalWised
Hi Diane,

You bring up something which is troubling for any pet guardian, how to ensure your vet is the right one for your animal. We understandably worry about our pets, but it can make it difficult to be objective about the situation. So, if you are worried about the quality of your pet's care, then you need to be objective as best as possible.

Has the vet been able to address other problems correctly in the past? Have you had doubts, but it turns out their advice was good? When you said you asked about drops and that it wasn't painful, was there evidence your cat was actually in pain?

If you can be objective as best as possible and you still think the vet is not giving your pet the right care, you can think about changing to a new one (we understand this may be difficult depending on where you live). We can't speak for any vet in particular, so it is up to you to assess the situation. If you are part of a cat network, maybe there are other people in this network who will be able to give you their experience with this vet?

In terms of specific advice on your cat's illness, we couldn't possibly provide it. Your cat has a clinical picture which cannot be appropriately described in an article comment. They need to be given a physical exam and have the correct diagnostic tests performed. When the nictitating membrane is showing, it could be due to a wide range of illnesses. Sorry we can't be more specific, but it would be irresponsible for us to do otherwise. Good luck with your cat and we hope they are able to get the right treatment they deserve. They obviously have an owner who cares for them very much which goes a long way in promoting their well-being.
Louise Eldridge
Our 18yrs old cat Pixie has a third eyelid in her left. Our Vet treated her first with ointment, then eye drops. It seemed to improve. A couple of days ago it appeared again, now she is been treated with steroids. If this doesn't help, our vet wants to do ct scan. I'm really anxious and concerns. 😔
Merle Manson
My cat is extremely active, playful and eats well. In the last 2 weeks he's shown third eye, when outside it completely disappears. He has always slept a lot during day and often sits with eyes half closed as if he's going to sleep. He's happy, doesn't like me going away from home which I do 3 days a week. He's possessive.
Thank you God bless Merle.
Administrador AnimalWised
Hi Merle,

We cannot diagnose anything here in the comments, only a vet can do that. In saying this, the third eyelid is a symptom of the conditions detailed in the article. If it is showing, it is likely there is something wrong. Even if it is a relatively minor ailment, it can worsen, so the best thing to do is take them to the vet.
The animal
My cat went to the vet today and they said she has herpes in her eye.. Do you know any causes or anything involved with this?
Administrador AnimalWised
Hi Makayla,

Unfortunately, the feline herpesvirus type 1 (FHV-1) is quite common in cats. As with all herpesviruses, the cat cannot get rid of it completely. It will either lie dormant or you can treat the symptoms. Where they got it almost always from another cat. This could be from licking another cat's face, sharing a litter box or even eating from the same dish. Fortunately, it is manageable, so take the vet's advice and your cat can still have a long and happy life.

Here is some more info to provide some background:
Long story short, i have 3 foster kittens, all came with URI and eye infections. All on meds. A week in my older cat stopped eating, drinking and was lethargic. I vrought him to the vet, they gave him fluids under the skin, amoxicilian, some shots at the vet and a blood test, 500bucks later and he was doing better.. now its days later and hes not eating he has had diarrhea from the amoxicillin he threw up yellow this morning and is very lethargic, but not as lethargic as last time. I can see a little bit of his 3rd eye lid. Also two nights ago my 2 adult cats were sitting in the window, when a stray came up and freaked them out. They started hissing and swatting at eachother, and stopped being friendly towards one another. In the morning the grasscutters came and that scares them. Both were in my bathroom cabinet.. also where Frankie, my sick adult cat likes to sleep. I thought that they were back to normal, but when frankie came out before it looked like it was to get away from lilly (his sister). I am tapped out of money. I dont know what to do... the blood test came back with everything normal, and he has been on amoxicillin every day 2x a day 1ml. Today is supposed to be his last day on it, and it will be bc im just about out of his meds. All of the kittens are still on amoxicillin and terramycin for their eyes. They came off of both for about 6 days and one started sneezing again and anothers eye swelled up and i saw her whole 3rd eye lid.. but this was while frankie was on meds. For the most part they have been seperated, the occasional slip happens when one runs through our feet going in and out of the bedroom. So thry have touched noses here and there. The kittens havent had there distemper shots yet, but my 2 are updated on all shots. They never received their nd distemper shots when they were kittens and the vet i brought to a year later said it wasnt a big deal. So now u know everything, please help! I dont have another 500 to give to the vet also we moved into our new apt about months ago. So my question is, is he sick, is it stress, could it be dehydration? is the amoxicilin even working? What should i do?
Administrador AnimalWised
Hi Erin,

Thank you for sharing and we are sorry to hear about your predicament. Unfortunately, as we point out in the articles we can't diagnose anything here in the comments, even with a picture.

You have done the right thing by taking hem to the vet and it seems like it was very necessary. Antibiotics are usually the only treatment for such infections and it is imperative that the full treatment be carried out without any breaks, otherwise they may not be able to properly fight the infection.

It is also important to remember that it takes some time for these antibiotics to work. Symptoms should start to clear, but they won't be gone completely immediately. If the bloods have come back negative, it is a good sign. It could be stress, sickness or dehydration, so ensure they have stressors removed from their environment and that they have access to plenty of water. These are things which should happen regardless.

Wait until the course is completed and trust your vet's advice. If they still show signs of illness, then you won't have much choice but to take them back. However, before you do, you should call the vet and speak to them about what is happening. If you have paid for treatment already, then they should speak to you about follow ups.

If your cat needs further treatment and you can't afford to pay it, then you will have to look into payment plans, emergency care and anything else offered. Also, speak to your local animal shelter. They will be able to offer the best advice and may even have some treatment plans available through them.

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