OBJECTIVES: Micro-invasive glaucoma surgery (MIGS) has carved out a niche in the primary open angle glaucoma (POAG) treatment pathway, filling an unmet need for safer glaucoma surgery without the risk profile of trabeculectomy or drainage implants. However, MIGS devices have different levels of efficacy and safety and surgeons must weigh the importance of the clinical outcomes and resource use in each patient and select the most suitable device. This study evaluates the budget impact of using a new ab externo drainage implant (Santen) for patients with mild-to-moderate POAG. METHODS: A budget-impact model was developed in Microsoft Excel 2016 from the UK NHS perspective to calculate the economic impact of switching POAG patients from current drainage devices or trabeculectomy (where eligible to switch), to the Santen glaucoma drainage device. Published estimates of filtration surgery volume was obtained from Hospital Episode Statistics data for the UK. Comparators, utilization, costs of care and resource use was obtained from published sources and in-depth interviews with 30 practicing glaucoma surgeons. Direct costs relating to the surgical procedure, outpatient follow-up and interventions, resource use, prescription eye drops and MIGS devices were included to determine cost savings over 1 year. RESULTS: Based on switching eligible patients from current drainage devices or trabeculectomy to the new glaucoma drainage device, the model showed a reduction in theatre time, consultant time, time for bleb needling required post-surgery, and clinic time for the management of hypotony. These reductions in medical resources result in overall cost savings. CONCLUSIONS: The new glaucoma drainage device is an efficacious, minimally invasive procedure that may provide cost savings by reducing the time for surgery and management of post-operative side effects.