Help with son's eye problem

I've been reading on here and there is a lot of good experience here. Maybe some has run into this. My 13 year old son is a swimmer. Swims 5-6 days a week, 2.5 hours a day. He's been swimming since he was 6. This year his training got taken up a notch and this fall he has been sick A LOT. Colds and a couple of sinus infections. However during/after this last sickness the upper part of his right eye swelled up. Swelled almost shut. We put him on antibiotics and very little improvement. He wasn't out of the water long but a couple of days. Then we took him out of the water and put him on stronger antibiotics. Some improvement, but looked like it was getting worse again. The opthamologist put him on a steriod pack and it got better immediately! Not all the way but better. The doctor said it isn't an infection, but something irritating the tissue around the eye. He was out of the pool for 2 weeks and the only thing that seemed to make it better was the steroid. As he's tapered down the steroid pack, it's kinda flared back up, but he went back to the pool as well. We do not want this to be swimming related. I cannot imagine telling him he cannot swim. Does anyone have any experience? I seem to think that if it was something with swimming it would have improved a lot with two weeks out of the water. He feels great. A little stuffy, but "normal" for him. I appreciate any comments or thoughts out there. Not swimming is not an option! Thanks!