Eye Color Can Change With Age
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April Holladay, HappyNews Guest Columnist

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
A: You get the idea. Changing eye color baffles people. It’s the most-asked question I get.
OK, all. Eye color can change over time because of age or, unfortunately, disease.
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.
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.