In group 2 , IOP was reduced from a mean preoperative value of 29.0 7.4 mm Hg ( n = 3.3 glaucoma medications ) to a mean postoperative value of 20.2 7.4 mm Hg ( n = 3.4 glaucoma medications ) and 18.5 6.6 mm Hg ( n = 3.5 glaucoma medications ) at 6 and 12 months , respectively .