Barbara Marquand is a staff writer at NerdWallet, a personal finance website. Email: bmarquand@nerdwallet.com. Twitter: @barbaramarquand.
The eye may change color due to alteration of genes in the cells of the iris. This is because of your DNA factors in the body. The gene alteration can cause the eye to change color from brown to green and vise verse. There is no any explanation to the cause of the genes behaving in these manner. Prolonged exposure to the sun might also be another cause that made my eyes to change the color.
Your iris gets its color from a pigment called melanin. It's what makes them blue, green, brown, or hazel. Less melanin leads to lighter eye color. More melanin leads to darker eyes. Sometimes, the amount of pigment in your eyes can vary: Complete heterochromia means one iris is a different color than the other.