Trabecular Micro-Bypass (Istent Inject) Protects Visual Fields, Retinal Nerve Fiber Layer Thickness, And Cup-To-Disc Ratio Through 5 Years

Intraocular pressure (IOP) reduction is central in glaucoma treatment, with the ultimate goal of halting or slowing glaucomatous damage. Three common measures of potential damage are visual fields (VF), retinal nerve fiber layer (RNFL) thickness, and optic nerve examination of cup-to-disc ratio (CDR).  Having reported IOP and medication reductions through 5 years, this large prospective real-world study further analyzed the dataset to determine 5-year stability of VF, RNFL, and CDR measures.  The rate of adverse events and additional glaucoma procedures were also evaluated. Stent implantation was performed with (Combined) or without (Standalone) phacoemulsification. 

This prospective single-surgeon consecutive case series evaluates iStent inject implantation in 125 eyes with predominantly primary open-angle glaucoma (POAG) and a substantial preoperative treatment burden.  Safety-specific outcomes included VF mean deviation (MD), RNFL thickness, CDR, adverse events and complications, and incidence of secondary filtering surgery. Outcomes were analyzed for the Combined and Standalone subgroups.

Five years after iStent inject implantation, there was no change in VF MD, RNFL, or CDR versus preoperative in either the Combined or Standalone subgroups.  In Combined and Standalone eyes, respectively, the preoperative vs 5-year measures were as follows:   average VF MD -6.6±2.8 vs -6.7±2.6 db (Combined, p=0.462), -7.0±3.5 vs -7.1±3.3 (Standalone, p=0.502); mean RNFL thickness 81.4±12.3 vs 80.2±13.5um (Combined, p=0.497), 82.1±13.6um vs 80.9±14.7um (Standalone, p=0.194); and mean CDR 0.74±0.17 vs 0.76±0.14 (Combined, p=0.324), 0.78±0.18 vs 0.79±0.16 (Standalone, p=0.386).  Five eyes (3 Combined, 2 Standalone) underwent a secondary procedure (cyclophotocoagulation or XEN).  No eyes underwent filtering surgery throughout 5-year follow-up.

iStent inject implantation resulted in preservation of key disease indicators (VF, RNFL, CDR) through 5 years, thereby demonstrating protection against the steady decline otherwise seen in this progressive neuropathy.  The protective effect was observed in both Combined and Standalone subgroups, and was accompanied by few mild adverse events and 0% rate of glaucoma filtration surgery.  Since outcomes were recorded in the doctor’s clinical population as part of routine care, they are directly relevant to surgeons and patients making treatment decisions in combined and standalone settings.  The data support the long-term utility of iStent inject in preserving patients’ visual function.