Monday Medical Issues: why do pets' eyes glow?

Okay, this isn't technically a medical "issue" - but hey, it's a cool topic!
______

If you’ve taken many pictures of your dog, cat or ferret, then you’ve seen it: laser eyes!

It’s a phenomenon specific to only a handful of animals; other species like rabbits, guinea pigs – even humans – just don’t genetically have that "special glow."

Those that do are gifted with a unique surface in the eye behind the retina called the tapetum lucidum. This special surface is composed of 15 layers of glittery cells that combine to create a single reflective layer to capture and enhance light.

Any light that gets past the retina is bounced back at it, giving the photoreceptors in the retina more data - and a second chance - to resolve the image.

Basically it functions a bit like nature’s very own night vision goggles! Cool, huh?

Why do Siamese eyes
glow red instead of green?

I had never really paid any attention to the color of the boys' eyes when they glowed until someone mentioned this to me. The claim was that Siamese eyes glowed red while all other breeds glowed green.

Of course, I had to test this empirically. So out came the camera.

Test Subject One: Allie

Yep, green!

Test Subject Two: Faraday

Look! Red eyes!

Test Subject Three: Maxwell

Seriously red eyes! We were shocked at how red, in fact.
(This photo undoctored)

Of course, that begs the question, what causes this?

Contrary to what Wikipedia states (you do know Wikipedia can be wrong, don't you?) Siamese cats do have that cool night vision layer behind their retinas. But unlike other breeds, there is a hereditary abnormality in Siamese that weakens the tapetum lucidum. So a Siamese cat probably won't see as well in the dark as other kitties.

Since Faraday is a Tonkinese (a blend of Siamese and Burmese), you'll notice his eyes are less red than Maxwell's. He probably sees better at night that Maxie.


So there you have it.
Cats: cool, built-in night vision goggles.
What's not to love?

____

Please don’t forget to keep nominating your favorite blogs for a Pettie Award and the chance to win $10K for a rescue or shelter of your choice. Nominations close on June 29th and you can vote once a day until then!
____

article sources:

"Hereditary abnormality in tapetum lucidum of the Siamese cats. A histochemical and quantitative study,"  Histochemistry, 1982;75(1):1-9. Published by National Institute of Health's PubMed site 

"Why do animals' eyes glow in the dark?" - NPR

"How Stuff Works"