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.
Some pigment causes the iris to appear blue. Increasing amounts of iris pigment produce green, hazel, and brown irises (or irides). There actually are two pigments, melanin and lipochrome, which determine eye color. Melanin (brown) deposition is controlled by a gene on chromosome 15.