Are you sure it is a permanent deafness? My dog Dirtnap had "nerve deafness". His hearing would come and go. The vet told me he could hear on occassion. It also helped that I cleaned out his ears with a q-tip. His ears were clogged soo badly I actually had to use ear wax remover and half pack of q-tips.
What type of dog is it? Deafness is a trait found in White dogs and Dalmations. Older White dogs for some reason get "deaf" sooner than other dogs. Dalmations are known to carry a "deafness" trait. So you may want to take this into consideration if thinking serious health issue is involved.
Deaf dogs can still live normal happy lives. They just have to be watched out or contained more. Some have taught "sign language" to their dogs if deafness is caught young. Vibrations or use of lights (like flash lights) may help in getting the dog's attention. The use of slow motions may be helpful as well. Fast movements will make the dog nervous.
All in all your dog should be okay and will find it's own way. You will be amazed at what they will teach you!!!