Glaucoma is a leading cause of blindness in the African-derived developing world and represents a significant public health challenge as the disease burden is substantial. In Ghana, the prevalence of open-angle glaucoma over age 40 is 8.5%. In Barbados, the prevalence is 7.0%. In neighboring St. Lucia, the prevalence has been estimated at 8.8% with a 16% ten-year incidence of glaucoma-related blindness in one or both eyes. (In contrast, the prevalence in US adults is 1.9%.) The burden of glaucoma-related visual dysfunction is also substantial in the developing world. Because the application of medical and surgical therapies is limited by issues such as cost, availability, and limited regional surgical expertise, undertreatment is pervasive. Also, there is little access to low vision or vision rehabilitation services and minimal social support for the visually impaired. Laser trabeculoplasty may be a part of the solution to the developing world's burgeoning glaucoma burden. The treatment is fast, safe, minimally invasive and requires minimal post-treatment care; the equipment is portable; and the incremental cost of trabeculoplasty treatment is small once the equipment and expertise are on-site. Our recent study in St. Lucia demonstrated that laser trabeculoplasty lowers IOP by an amount likely to favorably alter the clinical course of glaucoma (versus no treatment) and has the potential to bend the glaucoma-related blindness curve in the African-derived developing world. Our long-term goal is to translate this finding through a public health initiative by establishing a pan-Caribbean glaucoma laser program to provide safe, effective, and cost-effective therapy for glaucoma in this underserved and overburdened region. Before this can happen, several important research questions remain unanswered regarding SLT in this population and comprise the specific aims of this proposal. What is the long-term efficacy of SLT in this population? Is repeat SLT effective once the IOP reduction of initial SLT wanes? Are the results obtained in St. Lucia generalizable to other developing nations populated by people of African descent? In this application, we propose a prospective cohort study in St. Lucia in which qualifying subjects with open-angle glaucoma will receive bilateral selective laser trabeculoplasty, will be followed to failure of initial SLT, and will undergo repeat SLT and again be followed to failure. The long-term safety and efficacy of both initial and repeat SLT in glaucoma patients of African descent will thus be established. Further, we will replicate the cohort study in Dominica to confirm external validity of the St. Lucia outcomes. This proposal is designed to answer the questions posed above and thus to complete the research phase of this project and facilitate translation of the research findings into the public health space. Considering the population of the African-derived developing world, the prevalence of glaucoma in this population, and the observed preliminary benefits of laser therapy, this project's output could ultimately reduce the risk of glaucoma-related visual dysfunction in hundreds of thousands of individuals throughout the developing world.