It could be because of a not enough the watery secretion for the tear glands.
Yellow eye discolouration - Your eyes are the windows meant for health. Place a pencil between your back teeth but do not bite due. http://Jewelryframe.com/__media__/js/netsoltrademark.php?d=Www.Opticaljournal.com%2Fsleep-apnea-and-dry-eye-syndrome%2F