Background: Many countries face the challenge of a rising number of patients with or at risk of developing glaucoma. A test to differentiate between people who are unlikely to develop glaucoma and those at risk for the disease could be clinically useful. Ibopamine, when administered topically, temporarily increases aqueous production. Normal eyes with healthy trabecular meshwork show no significant change in intraocular pressure (IOP) following an ibopamine challen≥ however, those with glaucoma demonstrate elevated IOP. Design: The study was designed as a prospective case-control study in a tertiary hospital. Participants: Patients were recruited consecutively as they presented to glaucoma clinics at Flinders Medical Centre (n=39); the sample included 18 glaucoma suspects and 21 patients with glaucoma. All patients had open anterior chamber angles and no evidence of secondary glaucoma. Methods: Patients underwent IOP measurements followed by instillation of ibopamine 2% solution and subsequent repeated IOP assessment. The difference between the baseline measurement and that taken at 45min was determined and compared between groups. Main Outcome Measure: The outcome measure was the positivity of the ibopamine challenge test, defined by an increase in IOP>3mmHg. Results: We observed a mean increase in IOP of 1.9±1.6mmHg or 12.5±10.3%) for glaucoma suspects and 7.4±4mmHg or 52.4±26.5% for glaucoma patients (P<0.0001). Four glaucoma suspects (22%) and 19 glaucoma patients (90%) tested positive (P<0.0001). Conclusion: This study demonstrates that ibopamine has potential as a test to differentiate glaucoma suspects from patients with glaucoma.