Some cat owners have seen a pretty strange thing with their cats' eyes. They seem to roll back in their head, is that really what is happening to their cat?
It looks like the lower half of the eye turns white. Well, it's really not what it seems. What is happening is the nicating membrane or third eyelid has risen up on the eye, covering the lower part of the eye as it is raised. A lay term for this condition is called Haws Syndrome.
Cats have a third eyelid? Where is it normally?
Many animals have a third eyelid; cats are not at all special as far as third eyelids go. Dogs also have them, Haws is not as common in dogs as in cats. The third eyelid is just that, a third eyelid. The first two eyelids are the ones we normally see, being the upper eyelid and the lower eyelid. The third eyelid is positioned under the lower eyelid and for the most part goes unnoticed. Its function is to act as a windshield wiper, wiping the eye clean with every blink. The third eyelid has a large tear gland situatred on the inside which produces tear solution that washes the eye and keeps the eye moist.
How fast can Haws Syndrome develop?
The raising of the third eyelid can occur over a few days, gradually becoming more and more noticeable, or it can happen suddenly overnight. In severe cases, the entire eyeball is covered which often creates a level of panic for the pet owner.
Is just one eye involved or do both eyes get the same thing at the same time?
The true Haws Syndrome is bilateral, meaning both eyelids rise at the same time and for the most part look identical.
What causes Haws Syndrome?
That is a good question as most of the time, the third eyelid is normal and healthy, so the reason for the raising of the third eyelid has little to do with the condition of the third eyelid. When veterinarians see Haws Syndrome, they look at it much the same way as when they take a pet's temperature and there is a fever. The fever does not actually tell us why the pet is sick, but rather that it is probably not feeling well. The same can be said for Haws Syndrome, it is not feeling well, but why? There is no specific disease that consistently causes the third eye lid to raise and for and for that matter not all cats that are sick with the same disease will get Haws Syndrome.
What are some examples of diseases that are more likely to cause Haws Syndrome?
An eye injury or disease will cause that eye's third eyelid to raise, some neurologic diseases that involve the nervous system may trigger Haws. There are a multitude of systematic diseases which may cause Haws, some medications will aslo do it, especially tranquilizers.
How long does the Haws Syndrome last?
It may come on rather quickly, but usually takes weeks to go away. As a rule, the third eyelids return to normal when the cat is feeling better.