The third eyelid or nictitating membrane protects the eyes of our dogs, just like in cats, but it is not present in the human eye. Its main function is to protect the eye against external aggressions or foreign bodies that want to enter it. Humans, unlike animals, have our fingers to clean any particles that want to enter our eyes and that is why we no longer have this anatomical structure.
On our site we not only want to tell you about its existence, but also about the most common diseases or problems of the nictitating membrane or third eyelid in dogs. We will see symptoms and solutions in the necessary cases.
What is the third eyelid in dogs?
As we mentioned in the introduction, we find the third eyelid in the eyes of dogs and cats. In turn, like the other eyelids, has a lacrimal gland that hydrates it, also known as Harder's gland. This can suffer from a very common pathology in certain breeds that is its prolapse, also known as "cherry eye". This prolapse of the gland of the third eyelid or cherry eye is more frequent in breeds such as chihuahua, English bulldog, boxer, Pekingese, Spanish cocker or Neapolitan mastiff, among others, due to the conformation of the eye. It can occur in any breed but, especially, we usually see it in puppies or young dogs.
Structurally speaking, the membrane is a connective tissue hydrated by the aforementioned gland. It is not normally seen, but appears when the eye can or is in danger. There are breeds that can present a small pigmentation of the third eyelid, something completely normal. However, it does not have hair or skin that covers it, so sometimes it is not usually associated with an eyelid. It also has no muscles, is located in the medial angle (near the nose and below the lower eyelid) and appears only when strictly necessary, like a car windshield wiper. Therefore, its function will begin when the eye feels attacked, as a reflex action, and when the danger disappears it will return to its usual place, hidden under the lower eyelid.
Nictitating Membrane Privileges
The advantages provided by this membrane will not only be protection by eliminating foreign bodies that want to injure the eye or any painful principle, such as ulcers, wounds or injuries to the eyeball. It also provides hydration to the eye thanks to its gland that contributes 30% to the formation of tears, and its lymphatic follicles will help combat infectious processes, since it will be exposed when the eye is damaged until it has completely healed.
Therefore, when we see a white or pink film covering one or both of the dog's eyes, we should not be alarmed, it is simply the third eyelid helping to eliminate some ocular aggressor. We must bear this in mind and know that it must return to its place in less than 6 hours, if it does not, we must consult a veterinary specialist to see what may be happening.
Prolapse of the third eyelid in dogs
Although we already mentioned this pathology in the first section, as well as the breeds most prone to developing it, it is important to delve a little deeper into it. But, first of all, I want to remind you that it is not an emergency but you will need veterinary attention.
As we indicated, the prolapse occurs when the membrane remains visible, without returning to its usual place. The causes can be genetic or weakness of the tissues that contain it. It is one of the most frequent conditions in veterinary ophthalmology, which does not cause pain to the dog but can cause other pathologies as side effects, with conjunctivitis and dry eye being the most common.
There is no drug-based treatment for nictitating membrane in dogs, the solution is surgery with a small suture of the gland back in place. Likewise, the extraction of the gland is not recommended, since we would lose a large part of the hydration of the animal's eye.
