if one eye  is completely  gone then you must be very careful  about other eye . if by medication  the OPP is under control and after  refraction  he has useful  vision ie about 6/9 or so. or even if he is satisfied  with 6/12.then  you can wait  for some  time but monthly  check up of IOP is mandatory. if IOP is not under control  then 1st  glaucoma  surgery  and after some time  cataract  surgery or both surgeries  at a time are possible. but it should  be left  to the  operating surgeon. combined surgery is too safe .

Don't worry .u can check out if u can undergo cataract with glaucoma surgery.with recent advances the risks are lesser and combined surgeries are very commonly done. Delay in making decisions can be more harmful