Abstract
Purpose
To evaluate the 12-month outcomes of repeat XEN gel stent implantation in eyes with prior XEN failure.
Patients and Methods
This single-center retrospective chart review included 24 eyes of 24 patients with a previously failed XEN stent, who underwent repeat XEN gel stent implantation between April 2019 and June 2023. Outcome measures included changes in mean intraocular pressure (IOP) and number of IOP-lowering medications from baseline (prior to repeat XEN) to postoperative 12 months, assessment of surgical success defined as achieving IOP ≤18 mmHg without medications (complete success)/on the same or fewer medications (qualified success), without secondary surgical intervention (SSI), and a morphologically functional bleb.
Results
The mean age of patients was 65.3 ± 10.9 years. The study population was predominantly African American (79.2%). Among the eyes not requiring SSI, there was a 43.5% reduction in mean IOP from baseline to postoperative 12 months, which was statistically significant (23.50 ± 5.58 mmHg at baseline to 13.28 ± 3.54 mmHg at 12 months (p <0.001). The postoperative 12-month complete success rate was 16.7%, and the qualified success rate was 66.7%. The mean number of IOP-lowering medications also declined significantly from 3.00 ± 1.37 to 1.28 ± 1.13 (p = 0.002), revealing a 57% reduction from baseline to 12 months. No vision-threatening complications were reported.
Conclusions
Repeat XEN gel stent implantation may be a viable surgical option for prior XEN failure, providing meaningful reductions in IOP and medication burden in majority of patients. These findings support consideration of a second XEN stent before transitioning to more invasive filtering surgeries.
Keywords: glaucoma, minimally invasive glaucoma surgery, repeat XEN gel, intraocular pressure, IOP-lowering medications
Introduction
Glaucoma is a chronic, progressive, and irreversible multifactorial optic neuropathy and remains the second leading cause of blindness worldwide.1 The only proven strategy to slow disease progression is the reduction of intraocular pressure (IOP). When medical or laser therapies are insufficient to control the disease, surgical intervention is indicated. While traditional surgeries such as trabeculectomy and glaucoma drainage devices remain highly effective, they are associated with greater postoperative risk and a longer recovery course.2–4
The XEN gel stent (AbbVie Inc., Chicago, IL, USA) is a subconjunctival device designed to shunt aqueous humor from the anterior chamber into the subconjunctival space4 forming a bleb akin to traditional trabeculectomy.5–8 It has a better safety profile than trabeculectomy with the IOP-lowering potential of filtering surgery.9 Numerous studies have demonstrated that XEN stent implantation effectively lowers IOP and reduces medication burden.5,6,10–13 However, like all bleb-based procedures, it is subject to failure due to subconjunctival fibrosis.8,14–16 When this occurs, bleb needling is commonly performed to restore outflow. Reported needling rates range from 19.1% to 43.2%,3,6,8,11,12,17–20 with variable success rates (36.9% to 90.0%).6,8,20 In cases where needling or open revision fails, conventional filtering surgeries such as trabeculectomy and glaucoma tube shunts are typically considered the next step.
Historically, in cases of failed trabeculectomy, repeat trabeculectomy has been a recognized and effective intervention, with literature supporting favorable outcomes.21–24 Since the XEN gel stent is also a subconjunctival bleb-based procedure and relies on subconjunctival aqueous outflow as trabeculectomy, assessing repeat XEN stent outcomes after prior XEN stent failure is worth investigating. However, there remains a paucity of published data assessing outcomes of repeat XEN gel stent implantation following failure of an initial XEN procedure.6,25 Given the favorable safety profile and less invasive nature of XEN compared to trabeculectomy or tube shunts, repeat XEN implantation may represent a reasonable surgical option for eyes with flat scarred blebs that failed needling or open revision, or in eyes where a prior XEN stent fractures.
The present study aims to evaluate the clinical outcomes of repeat XEN implantation in patients who have experienced prior XEN failure. Specifically, this study examines changes in IOP and medication burden at 12 months and the surgical success of the second XEN procedure in a study population that predominantly comprised African Americans, a population more vulnerable to surgical failure.
Materials and Methods
This single-center, retrospective chart review included 24 eyes of 24 patients who underwent repeat XEN gel stent implantation between April 2019 and June 2023 at Omni Eye Services of Atlanta following failure of a prior XEN procedure. All initial and repeat procedures were performed by the same surgeon (AY). The study was approved by the Salus Independent Institutional Review Board (IRB) (ID number 24658), with a waiver of informed consent, as data were collected as part of routine clinical practice. No protected health information was collected, and anonymized data were used for analysis. The study adhered to the tenets of the Declaration of Helsinki.
Inclusion and Exclusion Criteria
Patients with a prior failed XEN gel stent who had undergone a second XEN implantation (adjacent to the first XEN) in the unscarred conjunctiva of the superior quadrant were eligible. Patients with at least 6 months of postoperative follow-up were included. Procedures could be performed as standalone or combined with cataract surgery. Exclusion criteria included prior incisional glaucoma surgery between the first and second XEN procedures or more than one previous XEN failure.
Surgical Candidacy and Technique
XEN stent-implanted patients who were deemed amenable to successful bleb needling or open revision (with reestablished flow) were not included. Repeat implantation was reserved for eyes with flat scarred blebs that failed needling or open revision, or if the prior XEN stent was fractured. The second XEN was placed in the superior quadrant in the unscarred conjunctiva adjacent to the first XEN, using either a closed or open conjunctival technique. The choice of surgical technique for repeat XEN gel stent implantation was left to the surgeon’s discretion. In general, the open technique was favored for more scarred/thicker Tenon’s/higher-risk conjunctiva or during a failed open XEN revision, while closed was used when the conjunctiva looked favorable. When the repeat XEN was placed using the open conjunctival technique, the prior failed stent was removed, the sclera in the area was cauterized, and the tract was closed to prevent fluid leakage. In closed conjunctival cases, the previously failed XEN stent was left in place. All eyes received an individualized dose of intraoperative subconjunctival mitomycin C (MMC).
Postoperative Management
IOP-lowering medications were discontinued postoperatively and reintroduced if IOP exceeded 18 mmHg. Bleb needling was performed as needed.
Outcome Measures
Collected data included demographic variables, glaucoma severity, interval between procedures, MMC dosage, lens status, and outcomes at 12±3 months. Outcomes included changes in IOP (measured using Goldmann applanation tonometer) and the number of medications from baseline to 12 months. At 12 months postoperatively, the complete success rate was defined as achieving IOP ≤18 mmHg without medications, no secondary surgical intervention (SSI), and a morphologically functional bleb. The qualified success rate was defined as achieving IOP ≤18 mmHg on the same or fewer medications, no SSI, and a morphologically functional bleb.
Bleb status was clinically assessed by the treating surgeon during routine postoperative examination. No formal standardized bleb grading system was used. For the purposes of this study, a functional bleb was defined as the clinical presence of an elevated subconjunctival bleb, consistent with functioning aqueous filtration through the repeat XEN stent. Bleb vascularity, avascularity, cystic appearance, and bleb extent were not formally graded.
The presence of a flat bleb despite achieving an IOP ≤18 mmHg or any requirement of SSI was considered a surgical failure. Additional success thresholds (eg, ≥20% IOP reduction) were also analyzed. Adverse events (eg, hypotony, choroidal detachment, hyphema, macular edema) and SSIs (eg, cyclophotocoagulation, filtering surgery, tube shunt) were recorded. Bleb revisions performed using the closed conjunctiva technique (needling) were not considered as SSIs.
Statistical Analysis
Statistical analyses were performed using SPSS v27 (IBM SPSS Statistics 27, IBM Inc., Armonk, NY). Normality was assessed via the Shapiro–Wilk test. Continuous variables were summarized using mean ± standard deviation (SD); binary outcomes were reported as percentages. Pre- and post-operative comparisons used paired t-tests or Wilcoxon signed-rank tests, as appropriate. The mean IOP and number of medications analyses were performed on patients who did not undergo SSI. Kaplan–Meier analysis was used to illustrate cumulative success over time. A p-value <0.05 was considered statistically significant.
Results
A total of 24 eyes from 24 patients with prior XEN gel stent failure due to flat scarred blebs underwent repeat XEN gel stent implantation and were included in this study. The mean age was 65.3 ± 10.9 years (range: 36–80 years), and the cohort was predominantly African American (79.2%, 19/24), with the remainder White (20.8%, 5/24). Full baseline characteristics are summarized in Table 1.
Table 1.
Baseline Characteristics of Patients
| Baseline Characteristics | |
|---|---|
| N | 24 |
| Type of glaucoma, n (%) | |
| Primary open-angle glaucoma | 21 (87.5%) |
| Chronic angle-closure glaucoma | 1 (4.2%) |
| Trauma | 1 (4.2%) |
| Other | 1 (4.2%) |
| Severity of glaucoma, n (%) | |
| Moderate | 6 (25.0%) |
| Severe | 18 (75.0%) |
| Repeat Xen, n (%) | |
| Open conjunctiva | 15 (62.5%) |
| Closed conjunctiva | 9 (37.5%) |
| Phakic eye status at the time of repeat Xen gel, n (%) | |
| Phakic | 7 (29.2%) |
| Pseudophakic | 17 (70.8%) |
| Type of procedure, n (%) | |
| Repeat Xen gel alone | 21 (87.5%) |
| Repeat Xen gel combined with cataract surgery | 3 (12.5%) |
| Needling prior to repeat Xen, n (%) | |
| Yes | 15 (62.5%) |
| No | 9 (37.5%) |
The average interval between the initial and repeat XEN procedure was 11.8 ± 13.3 months (range: 0.75 to 41 months), and the mean MMC dose used during the repeat procedure was 25.4 ± 11.4 mcg (range: 10–60 mcg).
At 12 months postoperatively, the complete success rate, defined as achieving IOP ≤18 mmHg without medications, no SSI, and a morphologically functional bleb, was 16.67% (4/24). The qualified success rate, defined as achieving IOP ≤18 mmHg on the same or fewer medications, no SSI, and a morphologically functional bleb, was 66.7% (16/24). The bleb needling rate was 12.5% (3/24). Three eyes that underwent postoperative bleb needling subsequently satisfied the qualified success criteria and were included in the qualified success rate of 66.7% (16/24). Qualified success without any postoperative reintervention, including bleb needling, was achieved in 54.2% of eyes (13/24).
IOP reduction of 20% or higher (from baseline) was achieved in 66.7% (16/24) of patients, and 70.8% (17/24) achieved a 12-month postoperative IOP of ≤18 mmHg. Additionally, 45.8% (11/24) of patients showed ≥20% reduction in IOP from baseline with a 12-month IOP of ≤18 mmHg on the same or fewer medications than at baseline.
Six eyes (25.0%) underwent SSI during follow-up, including 4 Ahmed valve implantations, 1 tube shunt, and 1 transscleral cyclophotocoagulation. Among the eyes (N = 18) that did not require SSI, the mean IOP decreased from 23.50 ± 5.58 mmHg at baseline to 13.28 ± 3.54 mmHg at 12 months, demonstrating a 43.5% reduction in mean IOP, which was statistically significant (p <0.001, Wilcoxon signed-rank test). The mean number of IOP-lowering medications was also significantly reduced from 3.00 ± 1.37 to 1.28 ± 1.13 (p = 0.002, Wilcoxon Signed-rank test) (Figure 1).
Figure 1.
(A) Mean IOP and (B) number of IOP-lowering medications at baseline (prior to repeat XEN gel) and at postoperative 12 months following repeat XEN gel procedure.
A subgroup analysis was also performed in patients undergoing XEN stent implantation with the closed or open conjunctival technique. The reduction in IOP and IOP-lowering medications from baseline to 12 months trended higher in the closed conjunctival subgroup (Table 2).
Table 2.
Descriptive Analysis of the IOP and Medication Reduction Achieved in the Open and Closed Conjunctival Subgroups
| Open Conjunctival Group (N = 10) | Closed Conjunctival Group (N = 8) | |||
|---|---|---|---|---|
| Intraocular Pressure (IOP) (mmHg) | Number of IOP-Lowering Medications | Intraocular Pressure (IOP) (mmHg) | Number of IOP-Lowering Medications | |
| Baseline prior to repeat Xen gel stent implantation (Mean ± SD) | 23.40 ± 6.64 | 3.30 ± 1.16 | 23.63 ± 4.34 | 2.63 ± 1.60 |
| Postoperative after repeat Xen gel stent implantation (Mean ± SD) | 14.00 ± 4.14 | 1.80 ± 1.14 | 12.38 ± 2.62 | 0.63 ± 0.74 |
| Mean change from baseline | 9.40 | 1.50 | 11.25 | 2.00 |
| % change from baseline | 40.2% | 45.5% | 47.6% | 76.2% |
Abbreviation: SD: Standard deviation.
The Kaplan–Meier survival analysis (Figure 2) demonstrated a cumulative 12-month qualified success rate of 66.7% (16/24), with a mean survival time of 9.8 months. Besides six eyes that underwent SSI, there were two eyes that did not undergo SSI but were considered failures. In one eye, postoperative 10-month IOP was 15 mmHg on 4 medications compared with 3 medications at baseline and at the Month 8 visit. Because the number of medications increased compared with baseline and the bleb also appeared flat, it was considered a failure at Month 10. In the other eye, postoperative IOP was 18 mmHg at 10 months, which increased to 21 mmHg on 0 medications at 12 months, with a normally elevated bleb. Because the patient refused medications, the IOP could not reach a threshold of ≤18 mmHg; repeat XEN gel in this patient was considered a failure at Month 12.
Figure 2.
Kaplan-Meier curve representing the survival probability of the study procedure for the postoperative 12 months.
There were no cases of postoperative overfiltration, as the sclera was cauterized and the tract was closed after removal of the prior failed XEN. No vision-threatening complications were observed throughout the 12-month postoperative period (Table 3).
Table 3.
List of Adverse Events and Secondary Surgical Interventions (SSIs) Observed in the Study
| Adverse Event/SSI | n/N | % |
|---|---|---|
| Adverse Events | ||
| Hypotony maculopathy | 0/24 | 0% |
| Endophthalmitis | 0/24 | 0% |
| Choroidal hemorrhage | 0/24 | 0% |
| Secondary Surgical Intervention (SSI) | ||
| Ahmed valve implantations | 4/24 | 16.6% |
| Tube shunt | 1/24 | 4.2% |
| Transscleral cyclophotocoagulation | 1/24 | 4.2% |
Discussion
This study presents the first dedicated analysis of repeat XEN gel stent implantation in eyes with prior XEN failure. Of the 24 eyes, qualified success was achieved in 66.7% of eyes at 12 months. This outcome is notable considering that all eyes in the cohort had previously failed a subconjunctival bleb procedure and represent a particularly challenging population of refractory glaucoma cases. The cause of failure was bleb fibrosis, resulting in inadequate IOP control and necessitating escalation to more invasive procedures such as tube shunt implantation or cyclophotocoagulation. This reflects the broader challenge of managing eyes with aggressive wound healing responses, particularly after subconjunctival filtration surgery.
Despite these challenges, the IOP and medication reductions were significant. Mean IOP decreased by 43.5%, and the mean number of IOP-lowering medications decreased by 57% from baseline to 12 months postoperatively. Furthermore, 66.7% of eyes achieved ≥20% IOP reduction, and 70.8% of eyes had IOP ≤18 mmHg at final follow-up. The bleb needling rate was remarkably low at 12.5%. These outcomes suggest that repeat XEN implantation can provide meaningful clinical benefit in a significant subset of previously failed XEN implantations.
The present study cohort comprised 79.2% African American. Prior literature has reported lower success rates following bleb-forming glaucoma surgery among patients of African descent.26–28 However, the acceptable success observed in this predominantly African American cohort suggests that repeat XEN implantation may remain a viable option in a population previously reported to be at higher risk for filtration-surgery failure.
In the present study, eyes underwent repeat XEN implantation with either an open or closed conjunctival technique. Descriptive analysis showed a greater reduction in mean IOP and the mean number of IOP-lowering medications in eyes undergoing repeat XEN with a closed conjunctival approach. The descriptive trends in this small cohort of repeat XEN implantation were contrary to those reported by Do et al, who documented a greater reduction in IOP and IOP-lowering medications along with a lower needling rate using the open conjunctival method for primary XEN gel implantations.29 This opposite trend in the present study might be due to selection bias, as the choice of surgical technique for repeat XEN gel stent implantation was left to the surgeon’s discretion. The surgeon may have selected an open conjunctival technique for relatively complex/higher-risk cases and a closed conjunctival technique for relatively easier cases. As such, our sample size was likely insufficient for meaningful statistical comparison.
Currently, when a XEN gel stent fails, the accepted surgical next step is trabeculectomy or implantation of a glaucoma drainage device. However, being more complex and invasive, trabeculectomy or glaucoma tube shunt may introduce more risk and unpredictable wound healing than repeat XEN stent. The results of the present study suggest that repeat XEN stent implantation in patients with prior XEN failure provided a meaningful reduction in IOP and the number of IOP-lowering medications in majority of patients. The favorable safety profile and short postoperative recovery associated with XEN, especially in comparison to traditional filtration surgeries, make it an attractive option in eyes that are still amenable to subconjunctival filtration. Although not evaluated in this study, in the author’s experience, a repeat XEN procedure may be considered a less invasive intermediate step before advancing to more complex and higher-risk incisional procedures. Future comparative studies may help confirm this hypothesis.
Literature supports XEN implantation in eyes with prior failed incisional glaucoma surgeries. For instance, Sheybani et al and Cheng et al reported IOP reductions of 36.4% and 59%, respectively, after XEN implantation in eyes with failed tube shunts.17,30 Similarly, XEN implantation in eyes with a prior failed trabeculectomy has shown IOP reductions of 23.5%–40%.31–33 While our study does not directly compare repeat XEN with other surgical options, the outcomes observed here align with those reported in such refractory populations, suggesting repeat XEN implantation remains a reasonable option.
Studies evaluating repeat trabeculectomy after failure of an initial trabeculectomy have reported favorable findings.22–24,34 Cankaya et al reported a 28.7% reduction in IOP in patients undergoing repeat trabeculectomy after a prior failed trabeculectomy.34 This success was attributed to the ability to further utilize antifibrotic agents—such as 5-fluorouracil and MMC—more aggressively after the second procedure in eyes with a robust scarring response observed after the first. Another study evaluating the outcomes of repeat trabeculectomy along with different exposure times of MMC in patients with prior failed trabeculectomy found greater IOP reduction (~55%) in a group receiving MMC for >3 minutes compared to a group receiving MMC for less than ≤3 minutes (~41%).22
All eyes in the present study received intraoperative subconjunctival MMC during repeat XEN implantation, consistent with common wound-modulation practices for bleb-forming surgery. However, MMC dosing was not standardized, cumulative exposure from the initial and repeat procedures was not directly analyzed, and no comparison group without MMC was available. Therefore, the contribution of MMC to surgical success or the observed needling rate cannot be determined from the present study.
The present study outcomes of repeat XEN gel stent when compared to previously published outcomes of primary XEN gel stent are also comparable. For instance, in the present study, 45.8% of eyes showed ≥20% reduction in IOP and 12-month postoperative IOP of ≤18 mmHg on the same or fewer medications than at baseline, which is comparable to 50% (using ab interno approach) and 46% (using ab externo approach) achieved previously with primary XEN gel implantation.35 As such, these findings suggest that XEN gel can be considered a viable surgical option to manage glaucoma before transitioning to more invasive filtering surgeries.
Additionally, the design advantages of the XEN device—including its small profile and minimal surgical trauma support its use in repeat procedures. These benefits may be particularly important for patients who are at high risk for complications from traditional filtration surgery.
The primary limitations of this study include its retrospective design, small sample size, which was not statistically powered, and lack of a control arm. While all procedures were performed by a single surgeon, ensuring surgical consistency, this may also limit generalizability. Furthermore, due to the nature of retrospective chart review, postoperative imaging, bleb morphology assessments were not standardized. Bleb assessment was subjective, unmasked, and limited to the clinical presence or absence of an elevated bleb rather than a standardized bleb morphology grading system. The small sample size and predominantly African American composition of the present cohort precluded assessment of race as an independent predictor of failure. MMC dosing was not standardized, and cumulative exposure across the initial and repeat procedures was not available for formal analysis, which precluded the assessment of the potential contribution of MMC dose or cumulative MMC exposure to surgical success, bleb function, or the need for postoperative needling. Finally, longer-term follow-up will be necessary to determine the durability of the results beyond 12 months.
Conclusion
The preliminary 12-month results of repeat XEN gel in carefully selected eyes with prior XEN gel failure, particularly those still amenable to subconjunctival filtration, are encouraging. Although one-fourth of the patients still required more invasive surgical intervention, the repeat XEN gel stent implantation provided a meaningful reduction in IOP and medication burden in the majority of the study population, who were predominantly African American, a demographic group at high risk of failure following glaucoma surgery. Surgeons can consider repeat XEN in carefully selected cases as a minimally invasive alternative before performing trabeculectomy or a tube shunt in patients with prior XEN implant failure. Further long-term data are required to validate the present study findings.
Acknowledgments
Raman Bedi, MD, critically reviewed the manuscript. IrisARC - Analytics, Research & Consulting (Chandigarh, India) provided statistical and editorial assistance in preparing the manuscript.
Funding Statement
Investigator-Initiated Study Grant from AbbVie. The sponsor had no involvement in the study design, methodological choices, data analysis, or reporting of results.
Abbreviations
IOP, Intraocular pressure; IRB, Institutional Review Board; MMC, Mitomycin C; SSI, Secondary surgical intervention; SD, Standard deviation.
Data Sharing Statement
The data that support the findings of this study are available from the corresponding author (Arkadiy Yadgarov), upon reasonable request.
Disclosure
AY is a consult for AbbVie; and reports consulting fees from IanTrek, SightSciences, Alcon, Glaukos, AbbVie, outside the submitted work. SW has no conflicts of interest to disclose.
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author (Arkadiy Yadgarov), upon reasonable request.