Why are the eyes blue?
Blue is extremely rare in nature. Aside from the feathers of some birds and the petals of some flowers, it is rare to see examples of blue in the natural world. Often, when blue manifests itself, it does so in the form of optical illusion. So, it might seem a little strange that some children have blue eyes. When we look at the sky on a clear day, it appears blue due to scattering of light, but not because the sky contains blue pigmented particles. Similarly, this is true for the blue eyes: it's about a structural coloring and not given by a pigment.
Read also: Newborn: when does eye color become definitive?
Blue is not dependent on a pigment
Il blue color of the eyes it is actually caused by the Tyndall effect, a phenomenon similar to the effect that makes the sky blue. The iris, the thin determining membrane of the eye, is composed of two layers of cells: the stroma above and the epithelium below. In blue eyes, the stroma is a translucent layer and contains zero pigments due to a genetic mutation: when visible white light hits it, it scatters the light waves.
The color is given by melanin
Blue travels through shorter wavelengths, causing it to be reflected more easily and therefore made more visible. The stroma in the Brown eyes contains high levels of melanin, a black and brown pigment, which means that the brown color is simply reflected back. As for the gray eyes, the phenomenon is similar to blue eyes, except that the stroma contains more collagen. This makes the layer less translucent and softens the blue undertones. Also for the green eyes, the Tyndall effect occurs. However, the stroma contains low concentrations of melanin, making the blue reflection darker and more greenish.
The color of children's eyes
All babies after birth have one color eyes blu ceruleo, which can change in the course before the first year of life. In the first months of life, if the melanocytes secrete little melanin, the baby will have blue eyes, if they secrete a little more, his eyes will take on the green or hazelnut color. With even more melanin, the baby's eyes will be brown or even black.Read also: How to protect children's eyes from the sun
When does eye color become permanent? The answer in the podcast
What color will the baby's eyes be? When does the color become definitive? Answered by doctor, midwife at Studio Intreccio Treviglio
- newborn 0-3 months