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.
What is surprising to me is that eye color doesn't change more often. Eye color is determined by lots of different genes but it all boils down to how much pigment you have in the front part of your iris at any one time. Lots of pigment means brown eyes, a little bit, blue eyes. Other colors come from intermediate amounts of pigment. The genes involved in eye color determine how much pigment gets made, how quickly it is degraded and where in your iris to put it. In other words, eye color is an ongoing process that is not necessarily set in stone. So all that has to happen to change eye color is to change the final amount of pigment in your eye.