Drug kept as a last reso in the management of primary open angle glaucoma is -
Latanoprost
Topical beta blocker
Brimonidine
Oral acetazolamide
Acetazolamide and methazolamide are not recommended for long term use because of their side effects. However, acetazolamide 250 mg Tds may be added to control IOP for sho term Ref :Ophthalmology A K Khurana 6th edition chapter-10 page no :237
Glaucoma