Ibopamine challenge testing becomes negative following successful trabeculectomy surgery.

Background: The ibopamine challenge test correlates well with a patient's peak diurnal intraocular pressure (IOP) measurement. We aimed to investigate the effect that a functioning trabeculectomy has on the ibopamine challenge test.

Design: Non-randomized prospective clinical trial evaluating a diagnostic test.

Participants: Thirteen patients were recruited through glaucoma clinics at the Flinders Medical Centre. Of these, seven required surgical management with trabeculectomy surgery, whilst the remainder were managed medically.

Methods: Patients underwent IOP measurement, and then two drops of Ibopamine 2% solution were instilled into the study eye of each patient. After 45 min, IOP was reassesed. A positive challenge test was considered to be a rise in IOP of greater than 3 mmHg. Changes from baseline were determined and compared between groups. Twelve months later, this test was then repeated in all patients.

Main Outcome Measure: Change in IOP after ibopamine challenge.

Results: Following the ibopamine challenge, IOP increased by 9.2 mmHg (SD 2.8) (100% positive) for medically managed patients and 7.2 mmHg (SD 2.0) (100% positive) for surgically managed patients (P = 0.18). The surgically managed group then underwent trabeculectomy surgery. Twelve months later, the ibopamine challenge was repeated. Following the repeat ibopamine challenge, IOP increased by 7.2 mmHg (SD 2.3) for medically managed patients and 0.3 mmHg (SD 1.3) for surgically managed patients (P < 0.0001). The medically managed group remained 100% positive, whilst the surgically manage group became 0% positive (Fisher Exact P = 0.044).

Conclusions: A glaucoma patient with a positive ibopamine challenge will show a negative challenge result when re-tested following trabeculectomy surgery.