Your eyes may be so dry. That is why you feel the eyes crust when you sleep. You need to use some eyes drops to release the eyes. At the same time, you should eat more food with vitamin C to moisture the eyes. You should not sit in front of the computers for a long time which will make your dry eyes get serious. You'd better have the good rest for the eyes.
In fact, eye crust can also be called rheum, and it is a common mucus discharge from the eyes. When you sleep and close your eyes, your eyes will still produce tears to keep moist and lubricated, meanwhile, the excess flows out at the corners and the lids of eyes and then become dry, resulting in the crust. Usually, the crust is a combination of tears, dirt and dust that get into your eyes during the daytime. However, some eye crust may be caused by conjunctivitis and infections, for example, pink eyes, this kind of eye infections can also produce many discharges from eyes, and it will easily forms crust over eyes. This kind of infection may also contains fungal infection called Canadians. In this case, you should take some antibiotic medicine to cure it. Because it is possible to get an eye infection from the crust as well, as the crust can act as a safe harbor for bacteria. Therefore, you'd better go to consult a doctor to help you. Hope you recover soon.