Primary Open Angle Glaucom 8 y/o

My question concerns my 8 y/o son with POAG diagnosis. Diagnosis in Dec '06, followed by a regime of drops.  Pressures seemed to be controlled ou.  OS IOP at onset was ~40 mmHg, OD ~ 25mmHg. Post trtmnt with Alphagan P BID ou, Azopt BID os pressures were ~15 ou. Last week os iop spiked to 50 (od ~ 16).  Diamox , timoptic xe, travatan were added ( Azopt stopped).  All exams show clear corneas, open angles, normal vf, corrected vision 20/20 od, 20/30 os, c/d ratio slightly worse in os (can't recall what they were)---otherwise healthy kid.  Next step would presumably be surgery.  I would like to exhaust all other options before sx.  Could the unilateral nature of this be indicative of some sort of something (venous flow problem)? In the abscence of any systemic issues (sturge-weber, others typically seen with glauc)) or other ocular issues are there other avenues to diagnose and/or rule out.  Would an MRI or MRA tell us anything? Could there be some sort of -oma lurking in there somewhere?  We are recieving excellent care and advice form our OD and Ophthalmologist, but would like to get additional input.
Any resources or advice you can offer is appreciated