If the whites of your eyes turn dark yellow, what does it mean?

Liver disease. Yellow sclera (the whites of your eyes) is called icterus which is an eye-specific form of jaundice. Jaundice is a result of elevated bilirubin which is caused by either liver disease or blockage of the hepato-biliary system (gallbladder, common bile duct, liver, and hepatic ducts). There are many causes of this. You should get it checked out by your doctor.
Icterus. Yellowing of the whites of the eyes could be a sign of significant liver disease. I would recommend going to see your regular doctor for evaluation.