Introduction. This analysis was performed to determine if early treatment of patients with Primary Open Angle Glaucoma (POAG) is cost-effective compared to late treatment.Results. Total discounted costs of early and late treatment were $7,107 and $5,608, respectively. Total vision years gained (VYG) were 13.07 for early treatment and 12.65 for late treatment. The incremental cost effectiveness ratio was $3,543/VYG. Results were sensitive to variations in disease progression, time horizon and yearly cost of treating patients with mild disease.Conclusion. Early treatment of patients diagnosed with POAG is a reasonably cost-effective choice, providing added years of vision.Methods. A decision analytic Markov model was developed using a 25 year time horizon. The perspective was that of the Ministry of Health and Long-term Care of Ontario. Health states were defined according to mean visual field (VF) deviation scores. Costs and outcomes were derived from the literature, discounted at a 5% rate.