If your student visa has expired and your current I-94 reflects "D/S" - Duration of Status you will be unable to return to the US without a new non-immigrant visa issuance from a US Consular Section abroad despite the fact that your EAD may still have a current validity date and you are on OPT. You should consult with an experienced immigration attorney to review your options before considering travel abroad, as you contemplate below, as well as discuss your situation with the DSO (Designated School Official) who has been handling your I-20 and OPT notifications through SEVIS.
Answered on Feb 13th, 2013 at 5:06 PM