I'm not being evasive, and that question has been asked before. It is not possible to generalize about retinal detachment surgery. They all are different. In some cases the person can return to full and unrestricted activities, in other cases a lot of restrictions are imposed. Only your retina surgeon can answer the questions you have posed. As a generalization a light back pack that you can easily carry (day pack) without straining would likely be okay but a multi-day maximum weight pack that his perceived as very heavy might be a problem.