Hoot is my doorbell. He can hear a car in the driveway and he alerts me, by the time he hears the bell he is already barking his head off. I can tell he uses his sense of smell to move around the house too. The kitchen smells like food LOL!
The other dogs sight is just fine. They see squirrels and rabbits in the yard from the windows in the den and they bark like crazy.
I take it you have a dog who is blind. I would never put down a dog who was either blind or deaf. They still enjoy so much of life. Unfortunately, all my dogs died too early for either their eyes or ears to conk at. They all died because of cancer or internal bleeding or something...