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.
1 Color-enhancement lenses are intended to shade your existing eye color. If you have light colored eyes, these lenses can brighten your natural shade or change it altogether. They may not have any effect on dark eyes, however.  Equinox lenses are lenses that have a dark ring around the iris.