In my country, it is OK to wear contact lenses when examing for the driving license. As you stated, your corrected vision with contacts can be 20/20, that is the perfect vision. But don't drive without any eyeglasses or contacts, for your bad vision may cause some miserable accidents.
At some place, you are required to have 20/60 acuity in at least one eye with or without corrective lenses. Some places require you to have 20/80 vision in at least one eye.Wjile at some other places, you need at least 20/40 vision iin at least one eye. So you'd better check out at your local place.