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.
Eye color also can change with age. This happens in 10 to 15 percent of the Caucasian population (people who generally have lighter eye colors). For instance, my once very brown eyes are now hazel, a combination of brown and green. However, some hazel eyes actually get darker with age. Note that if your adult eye color changes pretty dramatically, or if one eye changes from brown to green or blue to brown (called heterochromia), it's important to see your eye doctor.