Ibopamine challenge testing differentiates glaucoma suspect, stable glaucoma and progressive glaucoma cases

Background: An ibopamine challenge is a novel technique for assessing glaucoma using ibopamine, a topical drug which temporarily increases aqueous production. We aimed to determine whether change in intraocular pressure (IOP) and/or optic cup volume (OCV) during the test differentiated between glaucoma patients at different stages of disease; namely, glaucoma suspects (GS), glaucoma patients who are stable (SG) and glaucoma patients who have demonstrated rapid progression (PG). Design: Non-randomized clinical trial evaluating a diagnostic test. Participants: Sixty-one patients were recruited through glaucoma clinics at the Flinders Medical Centre (24 GS, 24 SG and 13 PG). Methods: Patients underwent IOP measurement and OCV assessment using optical coherence tomography. Two drops of ibopamine 2% solution were instilled into the study eye of each patient. After 45min, IOP and OCV were reassessed. Changes from baseline were compared between groups. Main Outcome Measure: Change in IOP and OCV after ibopamine challenge. Results: Following the ibopamine challenge, IOP increased by 1.8mmHg for GS patients, 4.5mmHg for SG patients (P = 0.003) and 8.1mmHg for PG patients (P < 0.0001). OCV increased by 0.2% for GS patients, 0.6% for SG patients and 5.5% for PG patients. This was not significantly different between GS patients and SG patients; however, it was significantly different between GS patients and PG patients (P < 0.0001), and between SG and PG patients (P = 0.001). Conclusion: GS patients may be differentiated from those with SG or PG by their IOP response, and SG may be differentiated from PG patients by their change in OCV following an ibopamine challenge.