The majority of patients with glaucoma do not take their medications as prescribed. Estimates of the cost-utility value of adherence to prescribed glaucoma medication are vital to implement potentially effective interventions.Cost-utility analysis using Monte Carlo microsimulations incorporating a series of Markov cycles (10 000 iterations per strategy).Patients with glaucoma aged ≥40 years with a full lifetime horizon (up to 60 years).The analysis estimated glaucomatous progression on the basis of data from the United Kingdom Glaucoma Treatment Study. Participants with glaucoma entered the model at age 40 years with a mean deviation in the better-seeing eye of -1.4±-1.9 decibels (dB) and -4.3±-3.4 dB in the worse-seeing eye. Participants whose glaucoma worsened each year accumulate -0.8 dB loss compared with -0.1 dB loss for those who remained stable. Data from the Glaucoma Laser Trial and the Tube versus Trabeculectomy Studies were used to assign probabilities of worsening disease among treated patients. Claims data estimating rates of glaucoma medication adherence over 4 years were used to assign probability of adherence. Those with poor adherence were modeled as having outcomes similar to the placebo arm of the clinical trials. As patients' mean deviation deteriorated, they transitioned between health states from mild (≥-6 dB), to moderate (<-6 to ≥-12 dB), to severe glaucoma (<-12 to ≥23 dB), to unilateral (<-20 dB) and bilateral blindness. At each health state, patients incurred the costs of treatment and established health utilities; ultimately, societal costs of low vision and blindness were included.Cost and quality-adjusted life year (QALY) of glaucoma medication adherence.Beginning at an initial glaucoma diagnosis at age 40 years, patients proceeded to single-eye blindness as early as 19 years among those who were nonadherent and 23 years for those remaining adherent. Total healthcare costs for adherent patients averaged $62 782 (standard deviation [SD], 34 107), and those for nonadherent patients averaged $52 722 (SD, 38 868). Nonadherent patients had a mean loss of 0.34 QALYs, resulting in a cost-effectiveness ratio of $29 600 per QALY gained.At a conservative willingness to pay of $50 000/QALY, there is room to expand services to improve patient adherence.