Long-term outcomes of two first-generation trabecular micro-bypass stents (iStent) with phacoemulsification in primary open-angle glaucoma: eight-year results

Abstract

Background: The short- and medium-term outcomes of iStent have been extensively studied; however, only few studies have investigated its long-term outcomes. Here, we assessed the long-term efficacy and safety of two iStents with concomitant cataract surgery in glaucomatous eyes while also evaluating measures of disease stability using visual field and optical coherence tomography (OCT) of the optic nerve and the macula throughout 8 years of follow-up.

Methods: This longitudinal, single-center consecutive case series included glaucomatous eyes that underwent implantation of two first-generation trabecular micro-bypass stents (iStent) with concomitant cataract surgery. Eight-year efficacy outcomes included mean intraocular pressure (IOP) and medications, as well as surgical success. Eight-year safety outcomes included best-corrected visual acuity (BCVA), visual field mean deviation (VF-MD), cup-to-disc ratio (CDR), retinal nerve fiber layer (RNFL) thickness, ganglion cell-inner plexiform layer (GC-IPL) thickness, and adverse events.

Results: A total of 62 eyes with primary open-angle glaucoma (POAG) were included. At 8 years postoperative, IOP reduced by 26% from 19.2 ± 3.9 mmHg preoperatively to 14.2 ± 2.4 mmHg (P < 0.001), 91.1% of eyes achieved IOP ≤ 18 mmHg (vs. 51.6% preoperatively), 69.6% of eyes achieved IOP ≤ 15 mmHg (vs. 14.5% preoperatively), and 25% of eyes achieved IOP ≤ 12 mmHg (vs. 1.6% preoperatively). Medication use decreased by 17.9% from 2.8 ± 1.1 preoperatively to 2.3 ± 1.2 (P = 0.018). Surgical success was 90%, as six eyes underwent subsequent glaucoma surgeries. Safety measures of BCVA, CDR, RNFL thickness and GC-IPL thickness remained stable through 8 years postoperative. VF-MD remained stable until postoperative year 5 and subsequently progressed according to the natural history of glaucomatous disease.

Conclusions: Implantation of two iStents with concomitant cataract surgery is an effective and safe treatment option for surgery-naïve POAG eyes, evidenced by significant IOP and medication reductions, reasonable surgical success, and favorable safety outcomes, throughout the 8-year follow-up. Our data additionally supports the efficacy of this combined procedure in stabilizing or slowing disease progression.

Keywords: Cataract surgery; Glaucoma; Long-term outcomes; MIGS; Minimally invasive glaucoma surgery; Trabecular micro-bypass stent; iStent.

Fig. 1

Change in intraocular pressure throughout eight years postoperative. * Denotes statistical significance at P < 0.05 and the error bars represent 95% confidence intervals. Mean ± standard deviations are presented

Fig. 2

Eyes with IOP ≤ 18 mmHg, ≤ 15 mmHg, and ≤ 12 mmHg, preoperatively and throughout eight years postoperative. Bars represent the proportion of eyes with IOP ≤ 18 mmHg (solid black bars), IOP ≤ 15 mmHg (checked bars), and IOP ≤ 12 mmHg (solid grey bars). IOP: intraocular pressure

Fig. 3

Change in the number of glaucoma medications throughout eight years postoperative. * Denotes statistical significance at P < 0.05 and the error bars represent 95% confidence intervals. Mean ± Standard deviations are presented

Fig. 4

Medication-free eyes and eyes with reductions of ≥ 0 and ≥ 1 medication(s), preoperatively until eight years postoperative. Bars represent the proportion of medication-free eyes (solid grey bars), eyes with medication reduction of ≥ 0 medication(s) (solid black bars), and reduction of ≥ 1 medication(s) (checked bars)

Fig. 5

Eight-year Kaplan–Meier survival chart. The cumulative eight-year survival was 90% for Criterion-A (dashed blue line; glaucoma reoperation due to inadequate IOP control or disease progression), 82% for Criterion-B (dotted green line; increased use of glaucoma medications at ≥ 2 visits), 56% for Criterion-C (dashed and dotted red line; selective laser trabeculoplasty), and 42% for Criterion-D (aggregate of criterion A, B, and C; solid black line)