A Prospective Analysis of iStent Inject Microstent Implantation: Surgical Outcomes, Endothelial Cell Density, and Device Position at 12 Months.

Abstract

The surgical outcome of iStent inject devices is associated with device protrusion within the anterior chamber. Schlemm canal (SC) dilatation has a prognostic value. iStent inject devices do not move within the first year after implantation. The iStent inject is a device designed to be implanted ab-interno through the trabecular meshwork. The present study follows up on our preliminary report, using successive in vivo anterior segment optical coherence tomography (AS-OCT) imaging to analyze the associations between stent positioning, iridocorneal angle structures, and surgical outcomes. In total, 54 eyes of 42 patients (73.3±7.4 y) with cataract and mild-to-moderate open-angle glaucoma were examined in this prospective study. All patients underwent implantation of 2 iStent inject devices combined with phacoemulsification. Patients were followed up over a 12-month period. AS-OCT was performed after 3 and 12 months. Thirty unoperated fellow eyes served as control eyes. Intraocular pressure (IOP) decreased from 16.5±4.2 mm Hg at baseline to 15.1±3.7 mm Hg at 12 months (-8.7%; P=0.004), while medications decreased from 1.8±1.0 to 0.5±0.9 (-72.2%; P<0.001). Unmedicated IOP≤18 mm Hg was achieved in 58.8% of operated eyes. No sight-threatening complications were reported. On AS-OCT, 44.9% of devices were buried within the trabeculum. Device position was unchanged between scans. Regression analysis elicited significant predictors: SC dilatation effect [risk ratio (RR)=0.230; P=0.003], greatest SC diameter (RR=0.991; P=0.049), extrusion of the most anterior device (RR=0.993; P=0.012), gonioscopically visible devices (RR=0.406; P=0.040), baseline treatments (RR=2.214; P=0.001), and baseline IOP (RR=0.184; P=0.006). Endothelial cell density decreased by 14.6% at 12 months (P<0.001). This study demonstrates the IOP-lowering and medication-lowering potential of iStent inject surgery in primary open-angle and pseudoexfoliative glaucoma. It confirms that surgical outcomes are positively associated with device protrusion within the anterior chamber, and suggests SC dilatation effect as a favorable prognostic indicator. It shows that stents are stable in time, highlighting the importance of the initial implantation location.