My eye is pink around the cornea the day after i slept in my contacts, why so?

Ciliary flush: Sleeping in your contacts increases the risk significantly for hypoxia and corneal infection. With the eye closed it becomes difficult for the cornea to get its oxygen and normal tear fluid. The blood vessels around the cornea (at the limbus) will get very congested and dilated because of the irritation. It is never recommended to sleep in your contacts.