I know how it feels to notice your dog is getting old. Just keep up with discipline and spend lots of time handling the dog physically. There is a white shepherd down the street who has gone blind in old age. I approach her slowly and give her plenty of time to recognize me. She growls pretty vicious when I first walk up to her. They need to get used to people touching them and walking with them when they can't see, so they don't become reclusive.