Standalone iStent Trabecular Micro-bypass Glaucoma Surgery: A Systematic Review and Meta-Analysis

Abstract

Precis: Standalone trabecular micro-bypass glaucoma surgery with the iStent devices is associated with clinically relevant reductions in intraocular pressure (IOP) sustained over a reasonably long-term while simultaneously reducing medication burden and a relatively favorable safety profile.

Purpose: While there is a relatively large body of evidence supporting the implantation of the iStent trabecular micro-bypass devices during phacoemulsification in patients with open-angle glaucoma (OAG), its efficacy as a standalone procedure has been less widely reported. The aims of this study were to systematically identify and quantitatively evaluate the efficacy of iStent devices (iStent and iStent inject) when performed independently of cataract surgery in patients with OAG.

Methods: A systematic review of the literature was undertaken in August 2019 to identify studies of standalone trabecular micro-bypass glaucoma surgery with iStent devices in patients with OAG. All randomized trials were considered and nonrandomized studies that included at least 6 months of follow-up or more than 10 eyes. Key efficacy analyses included postoperative IOP and medication use, which were used to evaluate weighted mean differences from baseline, and the proportion of eyes free of ocular medication. Postoperative adverse events were descriptively summarized.

Results: A total of 13 studies were identified including 4 randomized controlled trials and 9 nonrandomized or single-arm studies providing data for 778 eyes. In eyes implanted with iStent devices, a weighted mean IOP reduction of 31.1% was observed at 6 to 12 months. In studies reporting longer-term outcomes (36 to 48 mo or 60 mo), the weighted mean IOP reduction was 30.4% and 32.9%, respectively. The pooled weighted mean reduction in IOP from baseline across all studies at 6 to 12 months and 36 to 60 months poststent implantation was 7.01 mm Hg (95% confidence interval: 5.91, 8.11) and 6.59 mm Hg (95% confidence interval: 5.55, 7.63), respectively. Medication burden was reduced by ~1.0 medication at 6 to 18 months and 1.2 medications at 36 to 60 months. Adverse events reported in more than 5% of participants were progression of pre-existing cataract/cataract surgery and loss of best-corrected visual acuity but these rates were no different to those reported in comparator medical therapy study arms.

Conclusions: The results from these studies support the independent effect of the iStent trabecular bypass devices on IOP and medication burden over a duration of follow-up of up to 5 years.