REVALIDATION OF H, L, O AND P VISAS
The Visa Office can only revalidate the following types of visas: H, L, O, P, E or I. These visas can only be revalidated if your passport contains a previous visa of the same classification as the visa now being sought. If you do not have an existing visa in your passport of the same category that you seek, you can only obtain a new visa by applying at a U.S. consulate or embassy abroad or through the U.S. border post program.
Please note that B1/B2 (visitor), F (student) and J (exchange visitor) visas cannot be revalidated in the U.S.
If your existing visa is still valid, it will not be considered for re-issuance until the remaining validity is within sixty days of expiring. Please note that you do not require a new visa merely because you have changed employers and received a new I-797 petition from the USCIS. If your current visa is still valid, you may reenter the US with that visa as long as you are in possession of a valid I-797, even though the visa contains the information from your former employer.