Eye Color for Writers
May. 22nd, 2005 07:56 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
mishalakEye color is a polygenic trait. What the heck does that mean? Well first off it isn't as simple as the inheritance tables you made back in grade school when being taught the basics of genetics. And secondly it isn't well understood even by geneticists. Yet.
Blue is the basic "color" of eyes in humans over which all the other possible colors get overlaid. It isn't a pigment, but happens in the structure of the eye somewhat akin to the way that air preferentially scatters blue wavelengths to make the sky blue. Often (though not always) even albinos have blue eyes rather than pale pink eyes from the blood in the iris. Also note that if an iris has absolutely no pigment it can't block out enough light and makes it hard for the person to see in bright light and so those with the pink eyes need sunglasses or special contacts.
Aside from violet and grey all other colors are caused by pigment. The ever popular with Mary Sue writers violet eyes are thought to be a case of the eyes being pale or the stroma being thin enough to let the red of the blood show through a bit. Grey eyes are because of a tight and fine structure of the eye that scatters light more evenly across a range of wavelengths. Dark blue happens because of a coarse structure that strongly favors blue only. All of this is influenced by many genes and are still present even if there is a large amount of pigment in the iris.
Now we all know about melanin, the same friendly pigment that gives us brown hair and skin, causing brown eyes. This is why it is much more common for a person to have dark skin and brown eyes than to have pale blue eyes. Though it can happen, of course because it isn't just how much melanin a person produces but if it gets deposited in a particular place in the body. On the other end a person who is totally pale, blond hair, pale skin, is exceptionally unlikely to have brown eyes. Not enough is being produced even if the transport gene is turned on. And that leaves out developmental differences that haven nothing to do with genetics that can cause blue eyes in anyone. So while it is unusual it isn't always a sure sign of getting a bit on the side when two blue-eyed parents having a brown-eyed child. Or someone with one blue and one brown eye.
Now here's where it starts getting really complex. "Normal" melanin is called eumelanin is brown in color. Red hair is caused by phaeomelanin a sort of unfinished melanin that doesn't do a proper job of absorbing light. It has been suggested that this pigment is responsible for green eyes. Yet green eyes appear independent of red hair and most scientists identify lipochrome, a yellowish pigment that also causes some cases of yellow or sallow skin, as being responsible for green eyes. They only reason they often appear together is because the genes responsible are on the same chromosome and are likely to be transmitted together.
Now a person can have the gene for depositing whatever causes green eyes and also the other gene responsible for brown eyes. Then the stronger brown covers up the yellow without getting rid of it. And then there is hazel, the catch all for anything somewhere between brown, green, and blue. There is no clear information on if they're just a perfect balance between brown or so much yellow that it no longer looks green. They often appear in combination with flecks of green. Also that could be rays of color or flecks that are more extensive than with many people. It is often the case that people have a circle of a different color immediately around the pupil, rays of another color extending out from it, or at the edge of the white. So someone with lots of flecks of brown and blue might be said to have hazel eyes.
Obviously the rays and flecks can happen with green as well giving interesting blue green effects.
But no one has rainbow colored eyes that change color with emotions and I've only known one person that had eyes that changed from blue to green somewhat dependent on mood but much more on the color of what she looked at. (When looking at the sky or sea her eyes looked a lot more blue than green.) Sorry Mary Sues, you're going to be out of luck until someone invents some sort of "mood contact".
Blue is the basic "color" of eyes in humans over which all the other possible colors get overlaid. It isn't a pigment, but happens in the structure of the eye somewhat akin to the way that air preferentially scatters blue wavelengths to make the sky blue. Often (though not always) even albinos have blue eyes rather than pale pink eyes from the blood in the iris. Also note that if an iris has absolutely no pigment it can't block out enough light and makes it hard for the person to see in bright light and so those with the pink eyes need sunglasses or special contacts.
Aside from violet and grey all other colors are caused by pigment. The ever popular with Mary Sue writers violet eyes are thought to be a case of the eyes being pale or the stroma being thin enough to let the red of the blood show through a bit. Grey eyes are because of a tight and fine structure of the eye that scatters light more evenly across a range of wavelengths. Dark blue happens because of a coarse structure that strongly favors blue only. All of this is influenced by many genes and are still present even if there is a large amount of pigment in the iris.
Now we all know about melanin, the same friendly pigment that gives us brown hair and skin, causing brown eyes. This is why it is much more common for a person to have dark skin and brown eyes than to have pale blue eyes. Though it can happen, of course because it isn't just how much melanin a person produces but if it gets deposited in a particular place in the body. On the other end a person who is totally pale, blond hair, pale skin, is exceptionally unlikely to have brown eyes. Not enough is being produced even if the transport gene is turned on. And that leaves out developmental differences that haven nothing to do with genetics that can cause blue eyes in anyone. So while it is unusual it isn't always a sure sign of getting a bit on the side when two blue-eyed parents having a brown-eyed child. Or someone with one blue and one brown eye.
Now here's where it starts getting really complex. "Normal" melanin is called eumelanin is brown in color. Red hair is caused by phaeomelanin a sort of unfinished melanin that doesn't do a proper job of absorbing light. It has been suggested that this pigment is responsible for green eyes. Yet green eyes appear independent of red hair and most scientists identify lipochrome, a yellowish pigment that also causes some cases of yellow or sallow skin, as being responsible for green eyes. They only reason they often appear together is because the genes responsible are on the same chromosome and are likely to be transmitted together.
Now a person can have the gene for depositing whatever causes green eyes and also the other gene responsible for brown eyes. Then the stronger brown covers up the yellow without getting rid of it. And then there is hazel, the catch all for anything somewhere between brown, green, and blue. There is no clear information on if they're just a perfect balance between brown or so much yellow that it no longer looks green. They often appear in combination with flecks of green. Also that could be rays of color or flecks that are more extensive than with many people. It is often the case that people have a circle of a different color immediately around the pupil, rays of another color extending out from it, or at the edge of the white. So someone with lots of flecks of brown and blue might be said to have hazel eyes.
Obviously the rays and flecks can happen with green as well giving interesting blue green effects.
But no one has rainbow colored eyes that change color with emotions and I've only known one person that had eyes that changed from blue to green somewhat dependent on mood but much more on the color of what she looked at. (When looking at the sky or sea her eyes looked a lot more blue than green.) Sorry Mary Sues, you're going to be out of luck until someone invents some sort of "mood contact".
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(no subject)
Date: 2005-05-23 06:35 am (UTC)I have sunburst eyes.
CU
Don't forget this neat little toy!
Date: 2005-05-23 05:19 pm (UTC)