It not really detrimental at all. At least from my experience. He'll be able to do anything anyone else can. Itll just take a little more practice and a few different movements.
Truth I am from a biased perspective and I guess since I've had the good fortune to have my eyesight, It would be devastating to me. I wasn't trying to be insensitive, just trying to imagine the difficulty associated with both riding and coping with a blind eye.