Brown(?) Eyed Girl

November 10, 2011

Eva Gusnowski

Do you remember when we used to sing? Sha la la la la la la la la la la te da?  Well Mr. Morrison does, and I don’t know what he would sing about if all you brown eyed beauties tried a new procedure that will turn your brown eyes blue.


In days when the rains came, I did a little research on the function(s) of the various parts of the eye.  The pigmented part is the iris, and it is constricted and dilated by various muscles to respond to changes in light, in addition to other stimuli.  The iris becomes dilated, or open, when it needs to let in more light (in the dark), and constricts, or closes, when it needs to limit the amount of light that gets into the eye (in the day). 


Eye dilate


Those colored pigments aren’t just for show either.  First of all, the iris serves as a home for beds of blood vessels at its periphery.  Additionally, the colored pigment in the iris also serves a function.  The pigment physically blocks light from entering the eye, which makes sense, because what would be the point in constricting the iris if light is just going to get in anyway?  Structures in the body are there for a reason folks, and even the appendix is getting some much-deserved respect as of late.


The iris has two layers: a front layer and a back layer.  Interestingly, all eye colors use the same eye pigment (melanin), just in different quantities.  In brown eyes, both the front and back layers of the iris are filled with melanin.  In blue eyes, only the back layer is filled, while the front layer is left empty.  Green eyes have a full back layer and a glass-is-half-full front layer. The amount of melanin in the layers will give you all of the various shades in between.  The diffraction pattern of light hitting the iris is what gives the different pigment patterns their respective colors.  This also explains why two brown-eyed parents can have a blue-eyed child without blaming it on the mailman.  The genes that determine eye color can be thought of as “color packets”, since they determine the amount of melanin that gets deposited in the eye.  If your color packet holds more melanin, you’ll have darker eyes; if it holds less melanin, you’ll have lighter eyes.  It’s actually much more complicated than this since there are several genes involved in eye color, but this is the most straightforward explanation.


science in seconds, eva gusnowski, brown eyed girl


Down in the hollow, playin’ a new game is Dr. Gregg Homer.  He has developed a system whereby an image of the iris is used to guide a laser that destroys pigment in the front layer of the eye.  Because the pigment should not regenerate, a few weeks after the procedure the front-layer pigment will have been cleared away, leaving only the melanin in the back layer and…gasp!  Blue eyes!


But let’s not get too excited here.   There are a number of concerns that I think should be addressed.  First of all, Dr. Homer initially performed his experiments on animal test subjects.  Now, I definitely understand that basic science research often needs to be performed on animal subjects.  But this is for a purely cosmetic surgery…there’s no known or indicated health benefit that should be able to justify using animal subjects.  Secondly, research on live subjects has been performed in Mexico thus far rather than in the US and Canada, because “it takes longer to get regulatory approval [in the US]”, as stated in a BBC article regarding the laser treatment.  This sounds kind of concerning.  Lastly, there have been issues raised about the safety of the treatment, and whether destroying the melanin pigment will allow more light through to the retina.  There should still be pigment in the back layer, but how sure can you be that it’s not also being damaged.  Test subjects (in Mexico) have been followed for three months after surgery with no reported injuries, but I have to say that I’m still skeptical.  We may have to revisit this sometime in the future when there’s more data available.



So if you’re a brown-eyed girl, please stick to colored contacts, at least for now while the laser procedure is still in the “development” stages.  Van Morrison will still love you…you his brown-eyed girl.



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