Although many Siamese cats aren't cross-eyed, historically the trait was considered normal for the breed. Today, Siamese with and without crossed eyes exist. Whatever your preference, you can find Siamese cats with beautiful blue eyes that slant or look straight on.
The crossed eyes of the Siamese cat developed naturally to compensate for a genetic flaw in their eye structure. Interestingly, this same genetic trait causes the coloration of Siamese. Although the cat's eyes are not permanently crossed, traditional Siamese cats must cross them to see straight.
Cats' eyes point forward, like human eyes. Each eye has one spot that sees the same thing as the other eye. Nerves communicate the image to the brain, which puts the two together as one clear image.
Human retinas rest at the back of the eye straight on, so we look straight ahead to see. With Siamese cats, the left retina tilts in toward the right and the right retina tilts left. If the cat looked straight ahead it would see two different images. Siamese cats have compensated by crossing their eyes to place the retinas in line and to see more clearly.
Crossed eyes and a kinked tail are both considered natural to the breed; street Siamese cats in Thailand have them. Most if not all Siamese cats used to be cross-eyed.
However, the trait is less common among modern Siamese. Breeders have worked to remove it, along with the kinked tail.
If you're looking for a Siamese cat who's not cross-eyed, look for Modern Siamese. These are less likely to have crossed eyes, although the trait does pop up sometimes because it's genetic. Cats classified as Traditional or Thai Siamese haven't been bred to reduce the cross-eyed gene.
- Indiana Public Media Moment of Science: Why Are Siamese Cats Cross-Eyed?
- Domestic Cats: Their History, Breeds and Other Facts; Nancy Robbins
- Traditional Cat Association: The Traditional Siamese and the Classic Siamese FAQs
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