It is depends. it may caused by serious medical problems such as problems with the liver. Or your yellow eyes may caused by a mole in the eye. Though moles are collections of pigmented cells in the skin, they can also occurs in the whites of the eyes. If you have developed a new mole in the eye, you'd better visit an eye doctor or male sure it is not a cancer. Anyway, you'd better get your checked immediately for the sake of your health.
If you find the whites of your eyes are yellow, you'd better go to see a doctor as soon as possible because it might be a sign of some problems like jaundice or a liver problem. Or it may be caused by sun damage to the eyes. If the eyes are damaged by the sun, the white of the eyes will become yellow. All in all when the whites of the eyes are yellow, it means there is something wrong with you, you should visit a doctor to have a check.