My last horse, Sea Spray, was blind in one eye. Despite that she was an amazing jumper. She was really fearless and absolutly loved to jump with all her heart. Her eye never stopped us from jumping successfully. I agree with what others have said in that if he seems to enjoy it then go for it!
I used to jump Willow, and she also only had one eye. She poked it out while she was trying to escape from the place she was neglected at. She enjoyed it, and could jump either way, she just liked to turn her head a bit so she could see it as she approached it. She is very flexable so she could do this at a good canter, lol. I'm glad I'm not the only one who rides a one eyed horse! So many people tell me I'm asking too much of her, which makes no sense because she willingly does it anyways!
I think it would be more cruel to deny him something that he obviously enjoys doing just because he is handicapped. So long as he continues to be happy and willing, by all means, keep it up. Like other posters have said, he will let ya'll know when he is ready to start slowing down.
It isn't cruel to jump them with only one eye. We had a pony here who was a top level sj and developed a cornea in his eye that never came right. The eye was eventually removed. We thought that would be the end of his career but NOPE! He continued to compete at PGP level and won! At the height.
If he is happy jumping, you feel safe doing so, and are sensible enough to not jump him over ridiculously high/wide/terrifying jumps I see zero issue with it. Just be careful, but enjoy him :)
I personally think he looks very happy, and as long as you and him are both comfortable with jumping and competing, it is fine!! :)
Someone on her, MIEventer I believe(?), was telling a story about a horse that had been jumping and eventing at pretty high levels, and he had the same routine everyday. One day he fell over something, and when the vet came out they found out he had been blind for quite a while!