biology question #39
Andrea Rose, a 46 year old female from the Internet asks on July 25, 1999,Q:
Why do brown or blue eyes turn green in young adulthood?
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Maybe what you are observing has something to do with the ambient light or the clothing your young adults are wearing. Dr. Odiehog states on this eyecolor website: "Nearly all Caucasian infants have blue eyes. This is mainly due to the fact that there are very few "melanocytes", or pigment cells, in the iris. And those melanocytes that are present contain very little pigment. In black and brown races the iris stroma is more dense and the melanocytes contain more pigment, giving rise to a blue-gray appearance.
In all races, the pigment cells multiply as the child grows but if the cells contain little to no pigment the eye will stay relatively blue. So, in reality, there are no REAL blue-eyed people, just those that failed to develop brown pigmented melanocytes! Most of you with light-colored eyes have probably noticed a "spot" or two of brown on your eyes. These are clumps of melanocytes that happen to contain more pigment. These may be called "nevi" or just plain "freckles". They are not unlike those spots on your skin that you call freckles; just a clump of more highly pigmented melanocytes.
Now we know that a lot of pigment will produce a brown eye and that a lack of pigment will produce a blue eye. What about those green eyes? And the hazel? This is a little trickier. A light dusting of brown melanin cells on the iris will produce a yellowish color. Combine the natural blue with the fine scatter of melanin (yellow) and you'll get from a green to hazel color.
Image by: Freelance Illustration
Can your eyes really change color? Well, not really, but they certainly can appear to change. All of what we see around us is REFLECTED light. When you look at an object or even another person, you are actually receiving reflected light into your eyes. If that object was illuminated with red light, you would see that object as red, even though it may in fact be white. The melanocytes of the iris do not change (except in infants and the elderly) and therefore are not responsible for periodic eye color changes. The light around you does change, however, especially reflected light....from the color of the room, the sky, and your clothes." It turns out that eye color in humans is more complicated. At least two genes control eye color and they work in complicated ways. There may be more genes involved.
Many people visit this page because they want to change the colour of their eyes, perhaps by changing their diet. But that's not possible. The best way to change your eye colour is with colour contact lenses available at most optometrists.
According to a review of available web resources, it appears that babies and teens sometimes have eye color changes. Medication for glaucoma might cause color changes. Some believe that color changes are really just changes in refracted light, not actual color. Yet others claim migraines might be the cause of eye color changes. Here are some Web sites you can check.
- The Genetics of Human Eye Color, Answers to questions about eye color as well as resources
- MADScientist Network about changing eye color in adolescents.
- Eye specialist through Netwellness.org says:
1. Babies develop more pigment (melanin) as they age, so their eyes usually change from lighter to darker colors of blues or browns.
2. Some glaucoma medications (prostaglandins) disrupt the iris pigment cells, so they can cause some but not all iris quadrants to darken. This can be a big problem for blue and green-eyed patients; but brown-eyed patients rarely notice it.
3. Some patients are born with heterochromia (different colored irises); and others can develop it if they have certain neurological (Horner`s syndrome) or inflammatory (Posner-Schlossman syndrome) eye diseases. Source: Robert Newcomb, O.D., Professor of Clinical Optometry, Ohio State University
Be sure to also visit your local library to find resources on eyes and also check with your own optometrist.
A visitor named "blondie69" asks:
Is there any way to build the amount of melanocytes to make your eyes darker, say if they were a light green! Are there any vitamins you can take, like vitamin a,b,c,d, or e?
Dr. Carol Toris Director of Glaucoma Research in the Department of Ophthalmology at the University of Nebraska answers:
Prostaglandin F2a analogues given as eye drops to the eye can darken iris color in some people. These drugs do not increase the number of melanocytes but rather increase the amount of melanin in the melanocytes. These drugs were developed for glaucoma therapy and one interesting side effect is the darkening of iris color. It is noticeable mainly in eyes with brown color around the pupil and lighter color in the periphery. The result is a uniformly brown eye. This is not a common effect. The drugs are latanoprost, travoprost, unoprostone and bimatoprost.
A condition called Horner's syndrome causes the eye to become lighter. The sympathetic innervation to the eye is affected and this innervation is needed to maintain the pigment. People with one affected eye can end up with one light and one dark eye. Young children and animals may start out with light colored eyes that become darken as they age.
I know of no vitamin that darkens eye color. I wouldn't think you'd want to increase the number of melanocytes in the eye. If uncontrolled this could lead to melanoma which is a serious cancer.
There are many papers on iris color darkening. If you have access to Medline you could do a search and look through all those papers. Some of the authors are L. Bito, J. Stjernschantz, C. Camras, D. Albert.
You say that eyes can't change color. In my family, all of the women's eyes have changed color from brown to green! My sister's eyes changed very abruptly when she was 14 years old; both my mother and I have taken longer, with our brown eyes turning distinctly hazel somewhere around 40 and then getting gradually greener. My mother is over 80 now and her eyes are pale green. She has no health problems to speak of.
My father's eyes are green and so are my younger brother's. My older brother, who has a different father, has dark brown eyes still.
Stumbled across this page looking for answers to a question I've always had about my own eyes, and will corroborate that a person's eye color CAN indeed change somewhat over time, though I'm not certain how or why. I had distinctly dark brown eyes until about age 10, when they started to gradually become a light ambery brown; then by 15 they had much more green in them and have turned ever-so-slightly greener with each year. I have plenty of photos and relatives to confirm this, and it's definitely a more distinct change than can be accounted for by "surrounding colors", although I'm sure that has some effect too. I am 28 now, and my eyes are khaki or olive in color, but they appear as more of a pure, less muddy green when I wear green eye shadow or am in the sun. I haven't known whether to be alarmed about this gradual greenification. It has by no means been a sudden or drastic change, so I am not overly worried. Still, I am very curious about this and have hardly ever heard of it in other people.
My maternal grandmother has light blue eyes, but my mother was born with dark brown eyes, as have both of my sister and myself. When my mother was in her 20s she noticed her eyes becoming lighter and gradually a ring of green appeared around her pupil, which got larger until her eyes became a lovely hazel. They have stayed the same hazel for about 20 years now. The same thing has happend to both my sisters, though my eldest sister's eyes took longer because her eyes were so dark to be almost black. Now, I am in my mid-20s and have noticed my eyes are a lighter brown and have developed a small ring of green around the pupil, too. Eyes CAN indeed change color, without having anything do with surrounding/reflecting colors... but what scientists need to discover is WHY. This seems to occur more in women than in men, and also seems to be a hereditary thing... but we need to have scientific studies on this!
[This reader has done an exhaustive literature search on the subject and has summarized his findings here.]
The biggest problem is that there are different conflicting sources on eye color, usually old info vs new info, and the old info is never retired or revisited. From the info I gathered, as well as my best intuition, I would give this as a summary:
Regarding eye color: Red and Pink have no pigment and translucent/transparent stroma. The color is due to capilaries filtering light.
Blue has very little if any pigment (albinos commonly have blue eyes vs pink) The color is due to reflection of light from the stroma. Collagen in the iris reflects bluish-white light. Alignment and thickness of the cells and collagen fibers accounts for the wide variety of shades, patterns, etc.
Grey is effectively light blue
Green is effectively blue with a yellow pigment. This may be a sparse distribution of brown melanin This may be a yellow pigment, lipochrome/lipofuscin More research material is needed on phelomelanin vs eumelanin Research into whether there are people with yellow irii would be helpful.
Hazle is generally Green with more brown (eumelanin).
Brown and black are high concentrations of melanin blocking light.
Violet is rare but is claimed to be a cross between red and blue. If this is true, it would imply a thin layer of collagen, but a thick layer of other stroma cells, such that light would still be filtered to blue, but would pick up red from the capilaries as well.
A darker ring around the pupil is clamied to be an iridic blood vessel.
The pigment cells in the iris are derived from nerves and actually require innervation to maintain color.
Some people are born with different eye colors. Some people suffer trauma which causes one eye to be a different color. Some people find that their eye color changes slightly by mood or emotion. Since the hypothalamus is tied to mood and endocrine responses, this might be hormonal or it might be neurological, but there is insufficient refernece readily available to make this determination.
Read more at http://www.thetech.org/genetics/ask.php?id=30
I'm another whose eyes have shifted from a very dark brown in childhood to a definite green by the time I was 30. (Mother has dark brown eyes, Father has hazel eyes. My brother's are still brown.)
The overall change between my teenage years and the present is extremely clear. On my driver's license it says that my eyes are brown. In grade school I never questioned that my eyes were brown. Nobody who really looks at my eyes now says that they're brown. They're green with an orange star at the center.
I thought that I would add my two cents on here:). My mother has medium brown eyes, my father has blue, with a slight green tint. Now, my younger brother and sister have BRIGHT blue eyes. I had a lighter blue, but that began to change when I was about 14. They were to a blue green ( like my fathers), and now, at 21, they are entirely green, except for some brown surrounding the pupil and a blue ring around the iris.
I guess I will share my opinion on this. My grandfather and grandmother both were born with brown eyes. Some time over the years their eyes changed to blue. My backround is jatt sikh punjabi and most people from this area tend to have dark eyes. I'm 21 and today I was examining my own eyes and noticed I too have a thin blue ring around my brown eyes. I'm starting to wonder if my eyes will one day change color too like my grandparents.
I am a Latin 53-year-old male. About three years ago a pencil thin line of blue appeared on the perimeter of my dark brown iris. The blue line has now replaced about 1/4 of my original eye color. My ophthalmologist suggested I have high cholesterol levels and referred me to my doctor. My doctor tested me and my cholesterol levels are fine. He added that the color change is permanent and has no impact on my vision. My 83-year-old uncle's eyes have turned completely blue. My 65-year-old sister's eyes about 50% blue. Does this indicate that this is hereditary?
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