Jaundice is the most common cause of the whites of the eyes, or sclera, turning yellow. While jaundice refers to this happening in any part of the body, the formal term for yellowing of the whites of the eyes is icterus.
Jaundice is caused by a buildup of bilirubin in the body. According to the National Institutes of Health, bilirubin is a yellow-hued pigment found in bile. It is processed in the liver, released into the intestines and excreted through feces. When the liver or gall bladder are not functioning properly, they cannot process the bilirubin and it builds up in the body, resulting in jaundice or icterus.