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.
If hazel eye color is caused primarily by interference effects rather than by pigments, so they vary depending on the lighting conditions. but when the muscles around the eye contract or relax changes the shape of the eye opening. which affect the amount and angle of the light hitting the eye.