Foggy vision because of sleeping in contacts? when should eyes get back to normal?

Up to 12 hours.: I am of the opinion that you should never sleep with your contacts on. Even though the contact lens companies promote this, you are at greater risk of developing a corneal infection such as a corneal ulcer that can leave a permanent scar that might result in permanent decreased vision. I suggest daily wear disposable lenses. Remove your lenses immediately if you happen to sleep with them on.