The Ghana Primary Tube Versus Trabeculectomy Study

Inclusion Criteria: * Age 18 to 85 years, inclusive * Open angle glaucoma. Including primary open angle glaucoma, pseudoexfoliative and pigmentary glaucoma * Intraocular pressure 18 - 40 mmHg on maximal tolerated or maximal affordable medical therapy * Informed consent given and consent form signed. Exclusion Criteria: * Unwilling or unable to give consent, unwilling to accept randomisation, or unable to return for scheduled protocol visits * Pregnant or nursing women * No light perception vision * Previous incisional intraocular surgery, other than uncomplicated clear corneal cataract surgery * Previous ocular laser in study eye * Iris neovascularisation or proliferative retinopathy * Primary angle closure or primary angle closure glaucoma * Iridocorneal endothelial syndrome or anterior segment dysgenesis * Epithelial or fibrous downgrowth * Aphakia * Chronic or recurrent uveitis * Steroid-induced glaucoma * Severe posterior blepharitis * Unwilling to discontinue contact lens use after surgery * Previous cyclodestructive procedure * Glaucoma secondary to penetrating keratoplasty, trauma, retinal disease/surgery or neovascular disease * Conjunctival scarring from prior ocular surgery, trauma or cicatrizing disease precluding a superior trabeculectomy * Need for glaucoma surgery combined with other ocular procedures (i.e. cataract surgery, penetrating keratoplasty, or retinal surgery) or anticipated need for urgent additional ocular surgery