Eye color can change with age
Q: Is it possible for eye color to change as we age? My
aunt used to have brown eyes but now, at the age of 80, her eyes are green/grey.
My eyes seem lighter than before, too. Emily, Newport Beach, California
When I was born, I had dark blue eyes. As a child, my eyes
became hazel brown. Now that I am much older, they have turned a bright green.
Why are my eyes changing color so much? Judy, Kenner, Louisiana
I was born with brown eyes. They changed to olive green and
are now (I’m past 50) changing to light green and turquoise. Why does this
happen? Wanda, Memphis, Tennessee
What exactly are hazel eyes? I say hazel eyes change colors. I’ve read that
eyes don’t change color but how do you explain millions of people saying their
eyes change? Someone please explain! Bryan, Washington D.C.
A: You get the idea. Changing eye color baffles people.
It’s the most-asked question I get.
 Light
eyes. [National Eye Institute, National Institutes of Health]
OK, all. Eye color can change over time because of age
or, unfortunately, disease.
Eye disease is a cause of color change. So, ask a doctor to
examine your eyes if you notice a slow loss of color. The change could be due to
Fuch’s heterochromic iridocyclitis, Horner’s Syndrome, and pigmentary glaucoma,
says Brian DeBroff,
ophthalmology professor at Yale University.
Aging, however, is the usual cause of color change over time.
So, yes, Emily. Color can change as we age. It does so for 10 to 15% of the
normal Caucasian population. These people’s eyes change slowly over many years
after they reach adolescence.
Investigators considered Caucasians (non-East Asian,
non-Native American, non-African) because only Caucasians commonly have lighter
eyes.
"Some eyes become darker, but most become lighter with
increasing age," says
Richard A. Sturm,
a Principal Research Fellow at the Institute for Molecular Bioscience at the
University of Queensland in Brisbane, Australia.
And yes, Bryan, hazel eyes do change color. Hazel eyes,
as well as any lighter eyes, usually darken with age. Hazel eyes are light brown
or yellowish brown.
 The
basis of human eye color. Pigment cells (yellow in the figure) contain brown
pigment granules (shown in various intensities from neutral to light brown to
very dark brown). The lighter the pigment and the fewer the granules — the
lighter the iris color and the lighter the eye. The circles on the left depict
irises and the colors that result from the corresponding pigment cell. Blue
irises result from minimal pigment and few pigment granules. Green-hazel irises
have moderate pigment levels and number of granules. Brown irises have high
pigment levels and many granules. Information from Richard A. Sturm,
Institute for Molecular Bioscience at the University of Queensland.
How and why eye color changes.
Pigment in the front layer of the iris (called the stroma) colors the iris. Eye color lightens
when pigment granules drop in number, or when the granules make a lighter color. See figure.
The iris can also lose color if the pigment degrades.
Eyes, unlike skin and hair, do not synthesize color pigment
continuously. Instead, eyes keep pigment granules made earlier. So, if the pigment degrades, the eye color lightens.
Likewise, eyes can darken if the number of pigment granules
increase or if the granules make darker pigment.
That’s how the color changes. Why does it change?
Genetics is the key as experimenters learned by studying twins. They observed
the eyes and skin of identical twins and non-identical twins of American
Caucasians between the ages of 3 months to 6 years.
Both sets of twins showed a "darkening with age of both the
hair and eye colour," says Sturm. The identical twins changed color together, at
essentially the same rate. The non-identical twins changed color but at
different rates, which indicates a "strong genetic influence in the timing of
these colour changes."
Eye color probably changes for the same reason we have one
head instead of two: genes. Genes determine all body characteristics — including
changing eye color as we age.
Further Reading:
Eye color mocks easy rules,
WonderQuest
What exactly are hazel eyes,
and what color are they? WonderQuest
Molecular genetics of pigmentation by Rick Sturm, Institute
for Molecular Bioscience, University of Queensland
Oregon State University and Hewlett Packard: The genetics of
eye color
Anthro Limited: How are human eye colors inherited?
(Answered Oct. 8, 2004)
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