If you have the money or pet insurance, talk to your vet to find resources to help. If you can't afford that, you have to take a lot of time to work with you dog. As they are walking, physically guide them in a straight line. Also, when one sense is taken away, even with humans, another sense becomes much stronger. I'm sure your dogs sense of taste or smell is enhanced. Use the smell of a treat and have them follow the scent by placing it in a straight forward location. Your vet could give you a lot more ways to help without having to pay for therapy, just call them up and ask. Or make calls to several vets for advice and do what works best on your schedule