African Glaucoma Laser Trial

This study is designed to test the hypothesis that the efficacy of SLT is non-inferior to medical therapy and the effectiveness of SLT is superior to medical therapy for glaucoma. This is a prospective, multicenter, active-controlled, parallel-group randomized trial. One eye per subject is included in this study and is randomized 1:1:1 to one of three treatment arms: 1. SLT arm (provided at no cost) 1. Step 1: Initial 360 degree SLT 2. Step 2: Repeat 360 degree SLT 2. MED arm (provided at no cost) 1. Step 1: Latanoprost 0.005% once daily 2. Step 2: Adjunctive timolol 0.5% twice daily 3. RX arm (Usual Care- dispensed by prescription to be obtained at subjects' expense) 1. Step 1: Prescription for latanoprost 0.005% once daily 2. Step 2: Prescription for adjunctive timolol 0.5% twice daily Screening and baseline data are collected over two initial study visits. Baseline intraocular pressure (IOP) is determined and target IOP is calculated as a 20% reduction from baseline IOP and IOP \< 22 mmHg. Following the initiation of step one of assigned therapy, subjects in the SLT arm will attend a Week 1 safety visit. All subjects will be seen at Month 1 for the first efficacy evaluation, then again at Month 3 and then every 3 months thereafter through 36 months of follow-up. Eyes with IOP above target IOP at two consecutive visits during the first 12 months will be deemed to have failed current therapy and are advanced to step 2 of assigned therapy: * In the SLT arm, if step 1 (initial SLT) does not achieve or maintain target IOP, step 2 (repeat SLT) should be performed. One repeat SLT (two total) are allowed in the first 12 months following initial SLT; thereafter, SLT can be repeated as often as every 6 months. * In the MED and RX arms, if step 1 does not achieve target IOP, latanoprost therapy should be continued and timolol added. In all arms, if subjects fail step 2 of assigned therapy before Month 12, the subject is discontinued from study therapy, treated as deemed appropriate by site investigators, and continues to attend scheduled study visits and undergo safety-related study assessments. At Month 12, subjects in the SLT arm who have failed step 2 of therapy (repeat SLT) by Month 12 exit the study (as failure of 2 SLT treatments within 12 months indicates the subject is a poor candidate for further SLT). At Month 12, subjects in the MED and RX arms who are still active in the study (either still a success with Step 1 or 2 of assigned therapy; or failed step 2 but continue to attend study visits for safety assessment) will cross over to the SLT arm, discontinue medications, and undergo initial SLT. These subjects will attend a safety visit 1 week later and the first efficacy visit 1 month later. One repeat SLT (two total) is allowed in the first 12 months following initial SLT for those crossing over from the MED and RX arms; thereafter, SLT can be repeated as often as every 6 months. The primary outcome measure is intraocular pressure, which will be assessed by study personnel masked to treatment assignment during the first 12 months and to all prior IOP measurements at every visit.