My 10 year-0ld male Boston terrier developed an eye infection. The local vet put him on Tobramycin (a drug known to cause sudden deafness in dogs). In a couple weeks he was stone deaf. Is there any treatment to bring back some of his hearing?

No there isn't, since he's old.

Deafness caused by these types of drugs is usually irreversible. Very rarely it will resolve on it's own. Certain patients are susceptible to becoming deaf with these medications but there is no way to test for it.
Thankfully, living with a deaf dog is not very difficult, despite what a lot of people think. Here is a nice article about it, and you can talk to your vet further as well: Living with an Elderly Deaf Dog (http://miss-donna.hubpages.com/hub/Living_with_an_Elderly_Deaf_Dog)

No there isn't, since he's old.

Next time do some research before you reply. Your answer is not appropriate.