Not many. It is not uncommon for patients to develop low eye pressure after retinal detachment surgery. If the pressure is so low that it is affecting your best potential vision, you may require further intervention (evaluate for leaks, control inflammation with eye drops). Unfortunately, there are some times when the low pressure cannot be adequately improved. Speak with your surgeon about your options.
Supportive measures. In contrast to high eye pressures after surgery, for the most part, nothing is done to treat a low eye pressure after eye surgery unless there is a leak in the eye or increased pressure is needed for some therapeutic reason associated with the surgery, in which case the eye can be pressurized with fluid &/or inflammation can be treated less vigorously (which sometimes promotes higher eye pressure.
Big challenge! Too low eye pressure after retinal reattachment surgery is not very common, but occurs with increasing frequency the more surgeries were necessary to fix the retinal detachment. When it occurs, and the retina is attached, it is one of the biggest challenges in eye surgery today. There are no good or simple solutions. Even with best efforts, the too low pressure can only rarely be fixed.