AIM: To evaluate the cost-utility of iStent inject® with cataract surgery vs cataract surgery alone in patients with mild-to-moderate primary open angle glaucoma (POAG) in the Japanese setting from a public payer's perspective. METHODS: A Markov model was adapted to estimate the cost-utility of iStent inject® plus cataract surgery vs cataract surgery alone in one eye in patients with mild-to-moderate POAG over lifetime horizon from the perspective of Japanese public payer. Japanese sources were used for patients' characteristics, clinical data, utility, and costs whenever available. Non-Japanese data were validated by Japanese clinical experts. RESULTS: In the probabilistic base case analysis, iStent inject® with cataract surgery was found to be cost-effective compared with cataract surgery alone over a lifetime horizon when using the ¥5 000 000/quality-adjusted life year (QALY) willingness-to-pay threshold. The incremental cost-utility ratio (ICUR) was estimated to be ¥1 430 647/QALY gained and the incremental cost-utility ratio (ICER) was estimated to be ¥12 845 154/blind eye avoided. iStent inject® with cataract surgery vs cataract surgery alone was found to increase costs (¥1 025 785 vs ¥933 759, respectively) but was more effective in increasing QALYs (12.80 vs 12.74) and avoiding blinded eyes (0.133 vs 0.141). The differences in costs were mainly driven by costs of primary surgery (¥279 903 vs ¥121 349). In the scenario analysis from a societal perspective, which included caregiver burden, iStent inject® with cataract surgery was found to dominate cataract surgery alone. CONCLUSION: The iStent inject® with cataract surgery is a cost-effective strategy over cataract surgery alone from the public payer's perspective and cost-saving from the societal perspective in patients with mild-to-moderate POAG in Japan.