Our Pepper is completely deaf and if we touch her sometimes it scares her because she didn't know we were their. Perhaps your boy is going blind and just needs to know that it is you and he can trust you. I think you should work out a signal the you want him to come over by you. I think you probably already motion him over to you somehow. This will give him warning that you want him to come over and get pet. There is an old shepherd down the street from us who is going blind and when we get within range of her house she growls and I stop and let her come up to us so she knows who it is thats coming toward her. I hope the only problem is that he needs to know who is petting him and not that he is in any pain.