A Canadian cost-utility analysis of 2 trabecular microbypass stents at time of cataract surgery in patients with mild to moderate open-angle glaucoma

Purpose

To assess, from the Canadian public payer perspective, the cost-utility of implanting iStent Inject trabecular bypass stent (TBS) devices in conjunction with cataract surgery versus cataract surgery alone in patients with open-angle glaucoma (OAG) and visually significant cataract.

Design

Cost-utility analysis using efficacy and safety results of pivotal randomized clinical trial.

Participants

Modeled cohort of patients with OAG (83.1% with mild disease, 16.9% with moderate disease) and visually significant cataract.

Methods

Open-angle glaucoma treatment costs and effects were projected over a 15-year time horizon using a Markov model with Hodapp-Parrish-Anderson glaucoma stages (mild, moderate, advanced, severe or blind) and death as health states. Patients in the mild or moderate OAG health states received implantation of iStent Inject during cataract surgery versus cataract surgery alone. On worsening of visual field defect and optic disc damage, patients could receive selective laser trabeculoplasty and trabeculectomy. We measured treatment effect as reduction in intraocular pressure (IOP) and mean medication use and estimated transition probabilities based on efficacy-adjusted visual field mean deviation decline per month. Healthcare resource utilization and utility scores were obtained from the literature. Cost inputs (2017 Canadian dollars [C$]) were derived using the Ontario Health Insurance Plan, expert opinion, medication claims datasets, and Ontario Drug Benefit Formulary medication consumption costs. We conducted deterministic and probabilistic sensitivity analyses to examine the impact of alternative model input values on results.

Main Outcome Measures

Incremental cost per quality-adjusted life year (QALY) gained.

Results

Compared with cataract surgery alone, TBS plus cataract surgery showed a 99% probability of being more effective (+0.023 QALYs; 95% confidence interval [CI], 0.004 to 0.044) and a 73.7% probability of being cost-saving (net cost, –C$389.00; 95% CI, –C$1712.00 to C$850.70). In 95% of all simulations, TBS plus cataract surgery showed a cost per QALY of C$62 366 or less. Results were robust in additional sensitivity and scenario analyses.

Conclusions

iStent Inject TBS implantation during cataract surgery seems to be cost effective for reducing IOP in patients with mild to moderate OAG versus cataract surgery alone.