Efficacy And Safety Outcomes Of Ab Interno Vs. Ab Externo Xen Gel Stent Implantation In Open-Angle Glaucoma: A Systematic Review And Meta-Analysis

The Xen 45 Gel Stent is a Minimally Invasive Glaucoma Surgery (MIGS) device designed to reduce intraocular pressure (IOP) in patients with open-angle glaucoma by creating a subconjunctival drainage pathway. It can be implanted using either the Ab Interno or Ab Externo technique, each offering distinct advantages in terms of surgical approach, visualization, and potential complications. However, the relative efficacy, safety, and postoperative outcomes of these techniques remain unclear. This meta-analysis aims to systematically compare the clinical outcomes of Ab Interno versus Ab Externo implantation of the Xen 45 Gel Stent to guide clinical decision-making.

A Systematic Review and Meta-Analysis.

A comprehensive systematic search of PubMed, Embase, and Cochrane databases was conducted from inception to January 2025 to identify studies comparing Ab Interno and Ab Externo Xen 45 Gel Stent implantation. Dichotomous outcomes were pooled as risk ratios (RR) and continuous outcomes as mean differences (MD) with 95% confidence intervals (CI) using a random-effects model. Heterogeneity was assessed using I² and χ² statistics, with I² > 50% indicating substantial heterogeneity. Risk of bias was assessed using ROBINS-I. Publication bias was evaluated using funnel plots and Egger’s test. Statistical significance was set at p < 0.05, and all analyses were performed using RevMan 5.4.

Six retrospective studies including 435 patients (217 Ab Interno, 218 Ab Externo) were analyzed. No significant differences were found between Ab Interno and Ab Externo in IOP reduction (MD -4.93, 95% CI [-11.60 to 2.10], p = 0.17, I² = 95%), medication reduction (MD 0.79, 95% CI [-2.17 to 3.75], p = 0.60, I² = 99%), complete success rate (RR 0.93, 95% CI [0.85 to 1.01], p= 0.09, I² = 0%), qualified success rate (RR 0.91, 95% CI [0.67 to 1.23], p = 0.53, I² = 63%), complication rates (RR 0.99, 95% CI [0.74 to 1.33], p = 0.93, I² = 39%), visual acuity recovery (RR 0.37, 95% CI [0.08 to 1.79], p = 0.22, I² = 93%), or bleb needling rates (RR 1.15, 95% CI [0.85 to 1.55], p = 0.37, I² = 0%). 

Ab Interno and Ab Externo techniques for Xen 45 Gel Stent implantation demonstrate comparable efficacy and safety, with no significant differences in IOP reduction, medication use, success rates, complication rates, visual acuity recovery, or bleb needling rates. However, high heterogeneity in key outcomes and the lack of randomized controlled trials (RCTs) limit the strength of evidence. Variability in patient selection, surgical techniques, and follow-up duration may contribute to these inconsistencies. Well-designed prospective studies with larger sample sizes and long-term follow-up are needed to refine clinical guidelines and improve surgical decision-making in MIGS.