Concussion is usually caused by head trauma. In the meantime, head trauma can cause black eye too, if it is hitting in the face, especially near the eyes or nose. Usually black eyes is caused by bruise which could disapear within 3-5days. Yet if it happended along with concussion, it might indicate some other seriou injury in the head too, so be careful with it. And in this case, the black eye will take long time to disappear. You could take some action to speed up the process of heal. Stop any activity and put ice in a piece of cloth and apply to the area of the eye. Hope you could get well soon.
