My 6 y/o, Nate has PRA and is now pretty much sightless. His snarling and growling is focused on protecting his space in the house, so I've not dealt with the leash reactivity you face with your boy. I'd suggest searching this thread for the many great posts on managing reactive dogs. I think the approaches would be the same for dogs with and without sight.
I'll also mention that I got a great deal of help with Nate from Behave Atlanta . These ladies worked well with me via zoom. One is a trainer and one is a behaviorist. I noted when getting the link that they've got a waiting list this summer, unfortunately. However, they are a terrific resource that approached Nate's issues with intelligence, insight, and a gentle, positive philosophy.