Risk Factors For Failure After Trabecular Microbypass Stent

To assess three-year outcomes and risk factors for failure after iStent implantation combined with phacoemulsification.

Tertiary single-center cohort study in Toronto, Canada.

We performed a retrospective comparative study. We included adult patients with all types of open-angle glaucoma submitted to combined phacoemulsification and iStent from 2000 to 2018. Patients with previous filtering glaucoma surgery or less than one month of follow-up were excluded. The primary outcome was surgical success, defined as either medication reduction without an increase in intraocular pressure (IOP) or 20% IOP reduction with the same or less medication use. Multivariate analysis was conducted to elucidate risk factors for failure. Other outcome measures included IOP, medication classes, visual acuity, visual recovery, interventions, and complications.

A total of 145 eyes were included. The 3-year success rate for the cohort was 52.1%. There was a significant improvement in IOP (-2.7 ± 5.0 mmHg, p<0.001) and a decrease in glaucoma medication (-1.0 ± 1.5 classes, p<0.001) over the three-year follow-up. Prior trabeculoplasty was associated with a significantly higher risk of failure (adjusted HR, 3.41; 95% CI, 1.65-7.04). Eyes with advanced glaucoma were also associated with a greater risk for failure (adjusted HR, 2.47; 95% CI, 1.23-4.94). All patients recovered baseline vision or better. There were no severe complications.

There was a significant IOP decrease and medication reduction. Surgical success was obtained in 52.1% of patients in a real-life population at three years of follow-up. Previous trabeculoplasty and advanced glaucoma stage were risk factors for failure.