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 iris contains brown pigment, and the less pigment present, the lighter the eye color becomes. Diseases that damage the iris (inflammation, certain glaucomas...) can lighten it while tumors and freckles can darken parts. High corneal cholesterol can make the eye seem bluer.