Monday, July 9, 2012

Monday Medical Issues: Da Boyz are Albinos! Part 2

Yep, da boyz are albinos, as we discussed last week. Temperature-sensitive albinos, to be exact. That's what causes breeds like Siamese, Burmese, Himalayans and Tonkinese to have pointed coats - darker in the extremities and lighter in the torso.

But did you know this albinism extends to eye color, too?

There are two layers in the iris of the eye that determine what color your eyes are (both in humans and cats) – the stroma and the epithelium.

In most cats, pigmented cells are scattered throughout both layers. 

But for cats who have Siamese or Burmese alleles, (that gene pair we discussed last week that causes temperature-sensitive albinism) there is no pigmentation in the stroma.

And, whereas other cat breeds with blue eyes have pigment in that lower epithelial layer, the blue of a Siamese is due to the absence of pigment in both layers.

Whoa… if there's no color in Maxwell's eyes, why do they appear blue?

For the same reason the sky is blue.

(here you go, moms! the answer to the age-old question kids everywhere ask.)

In really basic terms it has to do with the fact that, of all the colors in the visible light spectrum, blue has the shortest wavelength, and colors with shorter wavelengths scatter more than colors with longer wavelengths – it's called Rayleigh Scattering. Since blue light is the predominant light that is bouncing around in the stroma layer, that is the color you see (shown by the cool red arrows in the diagram above!).

You can read more about it at Science Made Simple.

So there you have it, folks. Siamese cats: living out the answer to the age-old question of why the sky is blue.

Oh, and yeah. Da boyz are albinos!

"Ocular pigmentation in white and Siamese cats", Invest Ophthalmol Vis Sci. 1980 May;19(5):475-86. Thibos LN, Levick WR, Morstyn R.

Comparative Opthalmology, Chapter 11, UC Davis School of Veterinary Medicine


  1. Interesting post. Have a grand Monday.
    Best wishes Molly

  2. Wow! Now I want to know why Siamese, and so many other Meezer type kitties are so talkative!

  3. I never, ever knew that about their eyes!!! Sooooooooooo cool!

  4. Huh? This little kitteh is lost about why the sky is blue. MOL

  5. Isn´t it the same with Sacred Birmans ??
    Me too have pointed coat and blue eye´s.
    In the dark my eyes are glow red when some light gets to me :)

    1. Yes, you guys are temp-sensitive albinos, too! Kjelle, your eyes glow red for the same reason Faraday & Max glow red - your tapetum lucidum (cool, built-in night vision goggles)layer is thinner than other cats (see our Monday Medical from 2 weeks ago)!

  6. Goodness! you learn something new everyday!!!

  7. Wow, that is really interesting! Thank you for teaching us something new! :)

  8. Wow that is so cool! Thanks for this post, so great to learn something new about our kitties :o)

    new blog:

    1. Sarah, thanks! Hey guys, go visit Sarah - and buy a cool t-shirt to support the kitties!! 100% of the profits go to help cats!

  9. This is AMAZING!!!
    I was wondering the same thing about Kjelle Bus' eyes.
    Amazing too because these blue eyes are some of the most beautiful kitty eyes I've ever seen.
    (don't tell know how vain she can get.)
    xx, Glogirly

  10. Me thinks being a temperature sensitive albino is special. Mommy says when the light is right, my eye looks pinkish.
    Soooo, if wes albinos, why is our lips black? The Russian Blue?

  11. Moshe Moshi's Vet seem to think he is albino and I was surprised by that naturally because my expectation was that albinism would show the same on every creature (pale skin, pink eyes/ears). Your babies are no less beautiful.


Coolio! A comment? For US?