I have no help for you, but I do have a hen that is completely blind. Unknown reasons. No obvious injury. First one eye, then the other some time later. The second blind eye looks completely normal. But no sight. The first eye to go blind is discolored. ANYWAY, she lives a decent life, free ranges with the other birds, though doesn't usually go as far. Hangs more by herself when they all take off, but appears content. She knows where the food and water is, so she eats and drinks fine. I check her crop frequently and she is eating. Right now I have a broody that just hatched two chicks and when they are outside, they are in half the run with a gate to lock the other birds out. I put my blind hen in with her so she doesn't always have to wonder what is going on with the majority of the flock that she can't quite keep up with.
Point being: There is no cure for her blindness, but she is otherwise healthy and I have opted to keep her around as long as she continues to seem to want to continue. She also continues to find the nest boxes to lay eggs! The biggest downside is that she can't see the rooster approaching and doesn't have the option to refuse him like the other girls. Which is eliminated when she is hanging with the broody and chicks in the divided run.