Objectives To estimate the direct medical costs associated with the management of patients with primary open-angle glaucoma and to compare the costs of patients according to the degree of severity. Methods A longitudinal retrospective study was carried out using all patients with primary open-angle glaucoma that recorded follow-up from May 2010 to June 2013 at the Hospital Privado de Córdoba. We estimated the cost of the disease from the perspectives of the institution, with a bottom-up approach. Results The three-year follow-up after treatment of 104 patients revealed that the average cost of care for a patient with primary open-angle glaucoma was US$2746 ± 1560. The first year of treatment was significantly more expensive than subsequent ones (US$1100–$810–$827). Cost was related to the degree of severity of glaucoma; patients in “Stage 0” had significantly lower costs than those in other groups (Kruskal–Wallis test, p < 0.01). This was a consequence of lower costs associated with medication and a lower percentage of patients undergoing surgery. Discussion The direct medical costs of a patient with primary open-angle glaucoma vary according to the severity of their disease and the year of treatment. We found that costs increased with disease severity, but decreased over time.