The eyelid keeping an eye on your cat.

What in cat’s name is a third eyelid?

Some days, it’s only natural to feel like your cat’s from another planet, but did you know he actually has a third eyelid? And believe it or not, it’s not there to be kooky. The third eyelid actually plays an important role in keeping Rufus’s eye surface healthy, while protecting it. But sometimes this little eye candy becomes very easy to see, which could indicate Kitty has a health problem.

But have no fear, pet-lovers – we’re going to give you the whole cat-n-caboodle on what that third eyelid’s all about, and how to know if it’s eyeing a health problem. Read on.

What makes a third eyelid eye-catching.

What in cat’s name is the third eyelid, really? It’s actually known as a nictitating membrane, or fold of tissue at the inside corner of the eye, which is what makes it different to the first (upper) and second (lower) eyelid. The third eyelid is also covered in conjunctiva (the same tissue that’s on the white of the eye), and keeps its shape using a special T-shaped cartilage.

OK, so what does the third eyelid do, exactly – other than make us picture kitties in space? Well, it contains part of the tear gland of the eye, and produces heaps of the tear ‘film’. So, if your exploring Egyptian Mau gets a little dirt in his eye during his search for the pyramids (or more specifically, the little birdies that sit atop them), the third eyelid keeps the tear film strong, moving tears across the eyes, and pushing the debris out. This action, at the same time, keeps your cat’s eye lubricated and healthy.

Movement of the third eyelid is also partly controlled by your Cornish Rex’s sympathetic nervous system, and the muscle cells within the third eyelid, itself. For many other animals out there, this eye-catching feature helps protect the eye from injury – just as it would for Simba, as he moves through tall grass or captures pray.

How to spot the third eyelid: When your cat is alert, most of the third eyelid remains hidden in the eye socket, with only a small portion visible at the inner corner of the eye. When he’s relaxed, say, during naptime or while blinking, the retraction of the eyeball by a set of muscles causes the third eyelid to move across the eye surface, like it’s nothing at all, really.

So, now that you probably think a third eyelid is the coolest thing ever, guess what? You have ’em, too. But because we pet-lovers have a lesser need for eye protection, our third eyelid is really just a fleshy bump on the inner corner of our eyelids. Eye carumba!

What the third eyelid is trying to tell you. (Cue spacey music.)

The third eyelid also protects your cat by letting you know if ol’ Iris has a potential health problem. What happens is, the third eyelids come up – or ‘prolapse’ – causing them to be visible when your feline is already alert. Now, a number of hiss-worthy things can cause this, most of which don’t relate directly to the eyes. For this reason, you’ll definitely want to get Socket in to the vet to be checked over. In some cases, further laboratory tests are needed to find out the underlying cause of the third eyelid prolapse.

Some possible health issues related to the prolapse:

Eye disease: If your observant Oriental Shorthair has an infection or inflammation in one or both eyes, this could cause the third eyelid to prolapse.

High body temperature: If your haughty Havana Brown has a high fever – as opposed to cat-scratch fever – the third eyelid could cover his eye.

Dehydration: If your cat is old and thin, or dehydrated, and loses tissue around his eye, the third eyelid will prolapse.

Nerve damage: Nerve damage in your Norwegian Forest Cat’s face and neck will usually cause the third eyelid to prolapse in at least one of the eyes, although it is possible for the other to cat-along behind it. Where nerve damage is concerned, there are often other signs to go with this, such as a change in pupil size or loss of movement in your feline’s face. Hissss.

Intestinal upset. The most common cause of a third eyelid prolapse in both eyes, is when your cat has some sort of gastrointestinal upset – or cat-tastrophy, really – such as intestinal worms or other parasites; food intolerance; a viral or bacterial gut infection.

Now, if your vet has ruled out these reasons for your feline’s third eyelid prolapse, he or she may recommend treating your Bombay for worms, and checking he doesn’t have any other symptoms like diarrhoea, vomiting, or not eating. A special diet and medication could be the RX for your Devon Rex, or other tests may be needed (including faecal and blood exams). And just so you know, the third eyelid may stay elevated for 4-6 weeks after your peering Pixiebob has been diagnosed and treated. No hissy-fits needed – it will return to normal, eventually.

See, pet-lovers? If you keep your eyes open to what the third eyelid is telling you, your spacey Snowshoe will stay outta-this-world. Just the way you like him.

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