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.
The more pigment you have, the darker your eyes will be. Blue, grey, and green eyes are lighter because they have less melanin in the iris. Besides giving our eyes color, melanin helps protect them from the sun. Because they have less pigment, light eyes are much more sensitive to the sun's harmful rays than brown or black eyes.