To the best of the investigators' knowledge there have been no clinical trials to compare air and expansile gas in pneumatic retinopexy. The investigators hypothesize that both air and expansile gas have the same properties of gas and remain in the eye for 5-6 days which is long enough to have moderate chorioretinal adhesion to seal the retinal break. If the investigators can prove that air is equivalent to expansile gas in this procedure, it can save a lot of money for the country. Therefore, the investigators are conducting a randomised controlled double-blind study to compare the results of using air and perfluoropropane in pneumatic retinopexy for treatment of rhegmatogenous retinal detachment.