I am assuming he was operated for a retinal detachment , because vitreous detachment is not treated with surgery unless it has caused a non resolving vitreous hemorrhage. Coming to your question, he can do any of the activities he likes as long as he does not feel strain on the eye. Using his prescription glasses ( which is given after surgery), taking short breaks in-between and using lubricant eyedrops 3-4 times a day will help.

No such glasses The main motive to avoid long duration is to keep eyes from strain Otherwise vitreous can get detach again and can lead to RD