Yes, nearly all kittens are born with blue eyes, and that first blue is not permanent pigment. A kitten’s eyelids stay fused shut until roughly 7 to 14 days of age, and when they first open, the iris has no melanin in it yet, so light scatters off the clear tissue and reads as blue. That is a structural effect, not a pigment, the same reason the sky looks blue. Over the next 3 to 6 weeks, melanocytes in the iris begin producing melanin, and the true adult color (green, gold, yellow, copper, brown, or in some cats permanently blue) usually shows by 6 to 8 weeks and is fully stable by 3 to 4 months of age, within the neonatal development window described by the Merck Veterinary Manual (last reviewed 2022).
Evidence-reviewed, not hands-on tested.
When do kittens open their eyes?
Kittens are born with their eyelids fused shut, and like any baby mammal they need time to mature. Those lids separate at roughly 7 to 14 days old, which is why the familiar rule of thumb of around 10 days sits right in the middle of the normal window described by the Merck Veterinary Manual (last reviewed 2022). When you finally get a look at those eyes, they are a hazy blue, and that blue is not the color your cat will keep into adulthood. The iris simply has no pigment in it yet.
When do kitten eyes change color?
The shift starts between about 3 and 6 weeks of age, when melanocytes in the iris begin depositing melanin. Adult color is usually obvious by 6 to 8 weeks and fully stable by 3 to 4 months. Where it lands depends on how much melanin those cells lay down: yellow, green, brown, copper, or blue, with plenty of shades in between. One cat can even end up with two different colored eyes, called heterochromia, which the Cornell Feline Health Center (last reviewed 2018) reports most often in white cats, where the white coat gene keeps pigment from reaching one iris. These traits are set by the cat’s genetics, and eye color is defined tightly enough that breed registries write it into their standards: the Cat Fanciers’ Association Siamese standard calls for deep vivid blue.
Which cats keep blue eyes for life?
With that said, some cats are destined to have blue eyes permanently. The lack of pigment that appears blue is defined by their DNA as well. White cats sometimes have blue eyes that is associated with congenital deafness. In fact, up to 85% of white cats with blue eyes will also suffer from congenital deafness 1. That figure comes from the Cornell Feline Health Center deafness overview, last reviewed 2018. Sometimes the deafness will only affect one ear, so these cats may seem to behave normally. It seems that the gene for blue eyes is also associated with hearing.
Studies have suggested that some cats with permanently blue eyes (in this case, Siamese) have changes in their brains because of the difference that the lack of pigment makes in the way the eye handles light.² That work is Kaas, ILAR Journal, 2005, a peer-reviewed review of how the genes for coat and eye pigment reroute visual wiring in Siamese cats. Who your cat is, the way he hears, sees, and even looks are expressions of his genetic map.
So will my kitten’s eyes stay blue?
Adult eye color is written in the genes, but newborn blue is not the same thing. It works more like an optical illusion. Because the eyes are still developing, the pigment responsible for permanent eye color has not been deposited in the iris yet, so the eyes only appear to be blue. If you love those baby blues, don’t despair. If your kitten is meant to be a Frank Sinatra among cats, like the Siamese (in eyes and voice), it is already written on his genes and all you have to do is wait and see.
- Cornell Feline Health Center. Deafness. Last reviewed 2018. http://www.vet.cornell.edu/fhc/Health_Information/deaf.cfm
- Kaas JH. Serendipity and the Siamese cat: the discovery that genes for coat and eye pigment affect the brain. ILAR J. 2005;46(4):357-63. Review. PubMed PMID: 16179744.