I feel so badly for you, he seems very young to lose his sight. That said, if it has been gradual, his other senses have kicked in and he is probably doing fine. He doesn't feel bad for himself, for dogs "it is what it is" and they make do. When my 12 year old went blind, I hardly realized it she compensated so well. We even know a blind dog (catahula mix) who comes to dog park (he can see some light and dark) and he runs with the others, people don't know he is blind.
So grieve for all he is losing, but know that most blind dogs live good lives. Maybe no long off-leash runs, all on-leash now, you are his seeing-eye human. Just don't move the furniture!
Hugs to YOU on this day, and ear scritches for Sonny.