He will get used to it pretty easy. It depends on the horse but the majority of them have no problem with this. We have at the shelter three horses that are blind in one eye and they have no problem whatsoever. You should be careful when approaching them from their blind spot because they can get scared easy. But if you talk with him he should be ok. They get scared so they can become defensive.
We have a mare that it's completely blind in both eyes and she is fine too. She got used to it very well. When we move her in another pasture on in another place she is hitting herself pretty often until she becomes used to the environment. But she became pretty careful so she is walking slowly and she tries to touch everything with her nose. She is always moving with her head stretched in front of her so in this way she knows where the obstacles are before hitting them.
If you come with a bag of carrots she will find them without a problem even if you hide them well enough. She is better at it than the other horses. When you call her she is immediately starting to search you with her nose.
So I think that horses can have a wonderful life even if they are completely blind. You have to be more careful with them but they will adapt pretty easy to anything. This mare that I've talked about had no injury whatsoever in those 2 years that I've known her.