I was at my friend Jola’s house chatting. Day turned into evening as her eight cats frolicked about. Suddenly I noticed that one of the cats had red eyes - ruby, red eyes. I’ve seen him many times before, day and night, and his eyes are blue. But this night, his eyes were bright red. I looked at all the other cats, no other red eyes. I mentioned it to Jola, who said that she’s seen Stuart’s red eyes before, only at night, and not all the time. She has never seen another red eyed cat and can’t explain it.
I Googled “red eyed cats” and saw a description of red eyes in “odd eyed” cats (cats with one blue and one amber or other colored eye.) According to the article, the red eye is only seen in the blue eye, and is due to
“Tapetum lucidum” - a layer of tissue in the eyes of some vertebrate animals. It reflects visible light back through the retina and improves vision in low light.
Absence of melanin in the blue eye
Jola has other cats with blue eyes who did not glow red in the gloaming.
I’m hoping some eye expert can explain why only Stuart had the scary red eyes. (If it matters, Stuart is a Cornish Rex.)
Regular eye-shine in cats is caused by the tapetum lucidum.
Red-eye shine is caused by light reflecting off blood vessels, which will be more apparent in pale eyes because of the lack of pigment. Another factor however is the fact that the tapetum lucidum is generated by the same melanocytes that create color. So what sometimes happens is that blue-eyed cats are born without a tapetum as part of their mutation ( this is also the same issue with deafness in some white cats, where the maelanocytes are also instrumental in developing the auditiory nerve ).
No tapetum + pale eyes can = red eye shine. Note that not all blue-eyed cats are deaf or lack a tapetum lucidum. It depends on the type of mutation, as there are at least three different genetic ways to get a white cat, not all of which involve a lack of melanocytes. Siamese blue eyes and coat patterns for example are caused by a type of albinism and albinism is not associated with either deafness or a missing tapteum. But they might still have red-eye shine under the right conditions through simple lack of pigment.
I’ve mentioned my cat Bertram’s weird eyes before. One shines green, the other red. It’s very distinct if his pupils are dilated at all. His eyes are gold-green, for what it’s worth.
Thanks for your informative reply. One thing that really puzzled me, but which I didn’t put in my original posting, is why the red eyes suddenly appeared. I assume there had to have been a certain lighting level. As I said, I’ve seen Stuart (who is only partly white) many times, in both day and night, but this was the first time I’ve seen the red eyes. Anakin, who is a body double for Stuart and also has blue eyes, has never had red eyes, so apparently he lacks whatever mutation Stuart has.
But what brings out the red in Stuart’s eyes? It wasn’t just the way the light hit him in a certain spot. He moved around and still had the scary devil eyes.
Stuart is probably part Siamese. Siamese cats have blue eyes, and the lack of pigments in their tapetum lucidum that makes their eyes shine red. My Luna has blue eyes and red eyeshine as well, and she’s also only part white. She’s a Siamese mix.
Does Stuart meow a lot? Can he make a sound like a human baby crying? Did the non-white parts of his coat get darker as he got older? Those are other Siamese traits.
Eyeshine in cats only shows up if the light is just right. It’s a blue-green color in normal cats’ eyes, red in Siamese blue eyes. It is possible for a cat to have one eye with red eyeshine and one with normal green eyeshine (there’s a picture of this in the linked article). Siamese mixes don’t always look much like Siamese. Littermate cats can have different fathers, so it’s possible to have Siamese mixes and cats with no Siamese blood in the same litter.
Or he could be possessed. It’s not easy to tell with Siamese mixes, since they’re a bit devilish at the best of times.
