Eye color

Eye color is a polygenic phenotypic character determined by two distinct factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris.

Etymology

The term "eye color" is derived from the combination of the English words "eye", which is from the Old English "ēage", and "color", which is from the Old English "clor".

Genetics

In humans, the pigmentation of the iris varies from light brown to black, depending on the concentration of melanin in the iris pigment epithelium (located on the back of the iris), the melanin content within the iris stroma (located at the front of the iris), and the cellular density of the stroma. The appearance of blue and green, as well as hazel eyes, results from the Rayleigh scattering of light in the stroma, a phenomenon similar to that which accounts for the blueness of the sky called Tyndall effect. Neither blue nor green pigments are ever present in the human iris or ocular fluid. Eye color is thus an instance of structural color and varies depending on the lighting conditions, especially for lighter-colored eyes.

Eye color chart

The human eye color chart below shows the probability of eye color outcomes in children according to the eye colors of their parents. This chart is simplified and does not account for the genes of grandparents and earlier ancestors.

Parent 1	Parent 2	Probability of eye color in offspring
Brown	Brown	75% Brown, 18.75% Green, 6.25% Blue
Brown	Green	50% Brown, 37.5% Green, 12.5% Blue
Brown	Blue	50% Brown, 0% Green, 50% Blue
Green	Green	0% Brown, 75% Green, 25% Blue
Green	Blue	0% Brown, 50% Green, 50% Blue
Blue	Blue	0% Brown, 0% Green, 100% Blue

See also

• Iris (anatomy)
• Human genetic variation
• Population genetics
• Melanin
• Rayleigh scattering
• Tyndall effect
• Structural color

References

Eye color Resources
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