Nictitating membrane prolapse in cat – cause, symptoms& treatment


Did you know that your cat has one more eyelid than you?? Humans have a strongly movable upper eyelid and a slightly movable lower eyelid. The cat, on the other hand, has a third eyelid: the small conjunctival fold is called the nictitating membrane and is located in the corner of the eye on the side of the nose. The fact that your velvet paw does not blink is also due to the nictitating membrane, because it keeps the eye moist. Normally the nictitating membrane is not visible. If you see it anyway and it covers parts of the eye, something is wrong.

In our guide you will learn interesting facts about the cause, symptoms and treatment of the nictitating membrane prolapse in cats.

Nictitating membrane prolapse in cats: Brief Overview

  • Explanation:
    In the case of prolapse of the nictitating membrane the third eyelid of the cat falls forward and covers parts of the eye. The animal is visually impaired.
  • Causes:
    The triggers for the symptom nictitating membrane prolapse are manifold. The prolapse can be local or result from a general disease.
  • Symptoms:
    The nictitating membrane pushes itself on one or both sides over the eye resp. the eyes.
  • Therapy:
    The treatment depends on the trigger of the incident and can be accordingly quite different.

What is the nictitating membrane in cats and what is its function??

The nictitating membrane of the cat is also called the third eyelid or palpebra superior in Latin. The other two eyelids are the upper and the lower eyelid. Together they delimit the palpebral fissure of the eye.

The nictitating membrane consists of:

  • Conjunctiva:
    The conjunctiva is a mucosa-like continuation of the outer skin.
  • Nictitating cartilage:
    The cartilage is elastic and has an anchor-like shape.
  • Nictitating gland:
    The gland produces up to forty percent of the tear fluid of the cat’s eye.

But why does the cat have a nictitating membrane at all? The third eyelid is supposed to protect your pet’s eye from dirt and foreign objects. It moistens the cornea of the eye and, as mentioned above, produces slightly less than half of your cat’s tears.

Cause: Why does a prolapse of the nictitating membrane occur in the cat??

The prolapse of the nictitating membrane is a clinical symptom that can have many triggers.

Behind a prolapse can be diseases caused by bacteria, viruses or parasites. Often with the prolapse of the nictitating membrane comes a cat cold. If the prolapse is due to worms, your velvet paw suffers additionally from diarrhea and vomiting. Also a conjunctivitis, which your cat caught in the draught, can cause a prolapse of the nictitating gland. Even injuries, high levels of stress, and tremendous stress trigger third eyelid prolapse in animals.

Disorders of the nerves can also be to blame for the prolapse of the nictitating membrane

If your pet suffers from Horner’s syndrome, a neurological failure causes the nictitating membrane prolapse. Horner’s syndrome represents a complex of symptoms caused by damaged sympathetic nerve fibers. This means that not only the third eyelid is affected. You may also notice that your cat’s eyeball is sunken and the upper eyelid is drooping. The nerves in the whole area around the eye are damaged. In the cat, the syndrome most often occurs when the outer or middle ear is diseased.

In Haw’s syndrome, the prolapse of the nictitating membrane occurs suddenly on both sides. It is an innervation disorder of unknown origin. You do not recognize any other symptoms. Triggers are thought to be viral infections, parasites, and gastrointestinal disorders.

Some cats have very small eyeballs from birth. You are more likely to suffer a prolapse of the nictitating membrane. A serious warning signal is when the tissue around the eyeballs becomes less and less. This indicates other causes for the prolapsed nictitating membrane. Muscle atrophy, emaciation or lack of water over a long period of time may be behind it.

Allergies and intolerances can also be the reason for the prolapse of the nictitating membrane.

Below we have listed potential triggers

(Lists have no claim to completeness)

Possible local (local) causes of nictitating membrane prolapse in cats:

  • Local infection with cat cold
  • Conjunctivitis
  • Injury to the cornea
  • Foreign body in the eye

Possible systemic (affecting whole organ system) triggers for cat nip prolapse:

  • Bacterial infection
  • Viral infection
  • Worms
  • Disease of organs such as kidneys or liver
  • Metabolic disease
  • Allergies
  • Stress
  • Horner’s syndrome
  • Haw`s syndrome


A bilateral nictitating membrane prolapse is usually a sign of general disease, while a unilateral prolapse is more likely to indicate that this eye in particular is diseased.

From time to time, however, pet owners notice an incident of nictitating membrane that isn’t one. The treating veterinary surgeon then determines only a false prolapse with physiological normal findings. This is what happens when your velvet paw has a non-pigmented nictitating rim.

Psychological problems as a cause?

Relocation, bullying by other cats or a strong change in the daily routine stress your animal. For example, a new cat in the neighborhood may affect your furry nose. This stress is noticeable: Your velvet paw may eat less or nothing at all, it loses weight, refuses water. These are all alarm signals that you should take seriously. You can trigger a prolapsed nictitating membrane.

Important for cat health: Try to reduce the stress factors for your pet or best eliminate them completely!


Some scents have a calming effect on cats. You can try for example valerian or Matabi chewing sticks with active ingredients of the Japanese ray pencil..

Symptoms: How to recognize a prolapsed nictitating membrane in my cat?

If your cat is healthy, you will only see a small fold of the nictitating membrane at the inner corner of the eye near your cat’s nose. In case of a so-called nictitating membrane prolapse the third eyelid becomes clearly visible. The nictitating membrane now pushes far over the eye. You cannot overlook the prolapse. Sometimes even most of the eye is covered by the nictitating membrane. The prolapse may be unilateral or bilateral. You will notice that your cat is now more sensitive to light and produces a lot of tear fluid.

Reaction: what should I do if the nictitating membrane becomes visible in my cat?

Sometimes cats push the nictitating membrane forward when they sleep. This can happen once in a while, but should it be permanent, it may indicate disease. Your cat can not see normally, the vision is severely limited. This is dangerous for outdoor cats, because they can no longer perceive their surroundings properly. The prolapse can have a negative effect on overall vision.

Light sensitivity and poor eyesight put your pet under stress and pose a danger. The general condition of your animal will therefore possibly deteriorate quickly if the incident is left untreated.


Take your cat to the vet to find out the cause of the nictitating membrane prolapse!

Treatment: How to treat a cat with a prolapsed nictitating membrane?

The veterinarian orders a treatment, which depends on the cause. Nictitating membrane prolapse goes away on its own when the trigger is removed.


The prolapsed nictitating membrane itself is not treated, but the cause is addressed.

For example, if conjunctivitis is the reason for the episode, your cat will be treated with eye drops or ointment for the inflammation.

If necessary, the vet will take appropriate diagnostic steps such as blood or fecal tests. With this he wants to detect possible systemic causes. According to the examination results the veterinarian takes measures. Your velvet paw is then treated for example against bacterial or viral infections, parasites or deficiency symptoms.

If the vet suspects that Horner’s syndrome is the cause of the nictitating membrane prolapse, X-rays or CT or MRI scans may be necessary to make an accurate diagnosis.

If the reason for the prolapse of the nictitating membrane is an allergy or an intolerance, you change the food of your cat under professional guidance or change the attitude. In this way your animal will no longer come into contact with the allergens.


You can do prophylaxis:
Have your pet vaccinated against cat flu, for example, and have regular fecal tests and parasite treatments, if necessary!

FAQs – other frequently asked questions about the prolapse of the cat’s nictitating membrane

What do I do if the prolapsed nictitating membrane does not go away by itself??

In any case, you should visit your veterinarian and present the cat to him. He will examine it and find the reason for the prolapse of the nictitating membrane, so that it can be treated.

How long does a cat nictitating incident last??

As a rule, a prolapsed nictitating membrane lasts two to four weeks even if the trigger is treated.

Is a cat’s nictitating membrane prolapse dangerous?

The incident of the third eyelid of the cat is not life-threatening for the time being. The animal suffers however from the incident, since it does not see correctly any longer. Often there is a general disease behind the prolapsed nictitating membrane, which will permanently affect the health of the animal if you do not treat it. That is why it is important to have a veterinarian examine your cat.

How much does it cost to treat your cat for a nictitating membrane prolapse?

The question about the costs can not be answered flatly. The costs depend on the necessary examinations and treatment options. For example, if worms are the triggers for your cat’s nictitating membrane prolapse, the cost will be comparatively low. If the veterinarian initiates an X-ray examination or an MRI (magnetic resonance imaging) for an accurate diagnosis, it becomes more expensive.

The purpose and the costs of all examinations will of course be discussed with you in advance.

Can I treat the prolapsed nictitating membrane of my cat homeopathically??

The practitioner can try to help, for example, through certain acupuncture points, if the prolapse of the third eyelid of your cat is caused by Horner’s syndrome.

The association for veterinary naturopathy compiles on its website its members. You may find information about a homeopathic veterinarian in your area here.

Is the prolapse of the nictitating membrane of my cat contagious??

The prolapse of the nictitating membrane itself is not contagious. However, the disease behind it can be contagious – like cat cold or worm infestation.

Nictitating membrane prolapse. In: Lutz H, Kohn B, Forterre F, eds. Diseases of the cat. 6., updated edition. Stuttgart, Germany: Thieme; 2019.

Horner’s syndrome. In: Eul-Matern C, ed. Acupuncture for diseases of dogs and cats. 1. Edition. Stuttgart: Sonntag publishing house; 2015.

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