• Question: why do we have eye browns

    Asked by bonny123 to Blanka, Anil, Cees, Emma, Mike on 28 Jun 2012. This question was also asked by animals.
    • Photo: Blanka Sengerova

      Blanka Sengerova answered on 28 Jun 2012:

      Good question, bonny123.

      The reason why we have brown eyes is that we produce a pigment called melanin (it’s the same thing that makes you tanned when you’ve been in the sun) within our iris stroma (iris is the thing that has the coloured eye and the stroma is the liquidy region in front of it). The colour varies between brown and black, depending on the amount of the melanin.

      What I didn’t know and have just found out about is that apparently there are no blue or green pigments in eyes, but that the appearance of eyes as blue or green is due to the light scattering by the stroma, an effect similar to what makes the sky look blue.

      The colour of your eyes is determined by a complex combination of at least 15 genes (genes are basically bits of information on the DNA recipe book for making a cell) with the majority of human eye colour variation being explained by having different versions of a gene called OCA2.

      Does that answer your question?

    • Photo: Emma Trantham

      Emma Trantham answered on 29 Jun 2012:

      I think Blanka’s pretty much covered it all except I will just add that you might have seen some animals like mice or rabbits with pink eyes.

      This is because they are albino animals which means they have none of this melanin pigment. because they have no pigment you can see straight through their iris’ to the blood vessels at the back of the eye and that is why their eyes look pink/red

Comments

  • Photo: Emma

    Emma commented on :

    Although having just reread your question perhaps you meant why do we have eyebrows? In which case: the main reason is stop sweat, water and other stuff from dropping down into our eyes but they are also really useful for communication. For example if you raised an eyebrow in response to my answer to your question I would know I had got something about the answer wrong!