Did your vet think a fungal infection might be the problem? It's hard to tell if the drops were antibiotics (for a bacterial infection) or anti-fungal drops. Since this problem is going on so long, you might ask your vet to take some material from the ear and have it tested to find out exactly what you're dealing with.
Another consideration is food allergies. Talk to your vet about how to approach an elimination diet to figure out what, if any, food may be causing the problem.
I have the same problem with my Staffordshire. She has had this for years off and on. We have an ongoing prescription for Otomax, which is an antifungal type ointment. There is also an earwash, avail.to keep the fungus from growing. I use PetCareRX(they are cheaper than the vet and will fill your dog's prescription, you need only give them the vet's name, number, etc. and they will call them for the info on the meds your dog uses in the case of meds requiring a prescription. I know there are over the counter ear drops avail. for people which are supposed to combat fungus. I think it is Lotrimin.
Hope that helps!
Go back to the forums and check out the posts sent to Ear/Yeast Infection by Cryne. If you dont find it let me know.
My dog has ear issues too. So I went to the health food store.. Nutrition Smart, and asked them what I could do for my dogs ear infection. I think my dog has allergies and his ears hurt...but his ears are fairly clean all of the time. There was a lady customer who heard me asking the clerk about ear infections. So in lieu of hearing me,, she said I use Oregano oil for my ear infections...so she explained how to use it. Let me say that this works! Take a coffee mug.. mix 50% / 50% of oregano oil and olive oil. heat it up in the microwave for about 20 seconds give or take.. touch it to make sure it is not too hot! take cotton balls and put them in the oil mixture.. make cotton balls soak up oil.
Then, have some one hold the dogs head while u squeeze this in your dogs ears. I press it into my dogs ears like ear plugs and then let the dog shake the cotton balls out. This is the best wway so that it doesnt run into the dogs eyes.
THe warming of the oregano oil... is like a anticeptic.. if thats how u spell it, lol.
Hope this helps.. take care.