The objective of this trial is to evaluate the safety and efficacy of the Glaukos Trabecular Micro-Bypass Stent Model GTS400 (hereinafter referred to as GTS400) in combination with cataract surgery, compared to cataract surgery only, in subjects with mild to moderate primary open-angle glaucoma. This is a prospective, randomized, concurrently controlled, parallel groups, multicenter clinical investigation of the GTS400. Treatment will consist of either implantation of GTS400 stents in the study eye in conjunction with cataract surgery (Group 1, Investigational Group), or cataract surgery only (Group 2, Control Group). Clinical data through 12 months postoperative will form the basis of a pre-market approval (PMA) submission. Subjects will be followed for two years postoperatively.