Intraocular Pressure and Medication Changes Associated with Xen Gel Stent: A Systematic Review of the Literature

The Xen gel stent (Allergan Inc, an AbbVie company; Dublin, Ireland) was conceived as an option for patients requiring modest IOP reduction but for whom trabeculectomy was not yet indicated. As with any glaucoma surgery, establishing criteria for patient selection and identifying factors that contribute to a high likelihood of success are important. To help guide clinical decision-making, a systematic review of published studies on the gel stent was performed, with the goal of understanding postoperative outcomes based on clinical and patient factors. Results were organized around a series of pertinent clinical questions based on scenarios encountered in clinical practice. Criteria for including studies were intentionally broad, with the objective of simulating the diverse population of glaucoma patients encountered in real-world practice. Outcomes for IOP and medication reduction postoperatively were assessed in various analyses, including in eyes with various glaucoma types and severity; in eyes naïve to surgery as well as those with a history of prior incisional glaucoma surgery; and when surgery was performed as a standalone procedure or at the time of cataract surgery. The results of each of the various analyses were consistent in demonstrating that successful gel stent surgery achieved a postoperative IOP of approximately 14.0 mm Hg and reduction to fewer than 1 glaucoma medication. Additional data are shown on outcomes by method of implant (ab interno vs ab externo); intraoperative use of antifibrotics; and rates of needling in published studies.

Comparison of Clinical Outcomes Following Gel Stent Implantation via Ab-Externo and Ab-Interno Approaches in Patients with Refractory Glaucoma

Purpose

To compare clinical outcomes following gel stent implantation via ab externo and ab interno approaches in patients with refractory glaucoma.

Patients and Methods

This retrospective study included 203 eyes of 185 patients aged ≥45 years who underwent Xen gel stent implantation as a standalone procedure for medically uncontrolled glaucoma (intraocular pressure (IOP) ≥18 mmHg) despite maximum tolerable IOP-lowering medications. One hundred and five eyes underwent gel stent implantation via ab interno approach and 98 via ab externo. Patients with prior conjunctival-incisional glaucoma or cataract surgery were also included. Study parameters were reduction in IOP and number of IOP-lowering medications from baseline to 3, 6, 9 and 12 months postoperatively.

Results

There were no statistically significant differences in the age, sex, preoperative IOP, number of IOP-lowering medications or cup–disc ratio between the ab interno and ab externo groups at baseline (p > 0.05). At all postoperative time points, mean IOP and percentage reduction from baseline were comparable in both groups (p > 0.05) except at postoperative 6 months when the outcomes were significantly better (p < 0.05) in the ab externo group. The rate of postoperative procedures (5-Fluorouracil injections and bleb needling), the incidence of numerical or clinical hypotony and adverse events were comparable in both groups (p > 0.05). The mean number of IOP-lowering medications was comparable in both groups at all time points.

Conclusion

The Xen gel stent, whether implanted ab interno or ab externo, is effective in reducing IOP and dependence on topical medications in eyes with refractory glaucoma. The stent may be used in both phakic and pseudophakic patients and is a reasonable option for patients with prior failed trabeculectomy.

Optical coherence tomography-guided early postoperative management of XEN Gel implant

This interventional case series demonstrates the usefulness of anterior segment optical coherence tomography (AS-OCT) in guiding early postoperative management following XEN45 Gel Stent implantation, in conjunction with intraocular pressure (IOP) readings and slit lamp findings. Three primary open-angle glaucoma patients undergoing XEN45 Gel Stent implantation were included. Two patients received early postoperative needling because the IOP was not low enough and AS-OCT revealed that the XEN stent orifice was trapped by the Tenon's capsule. Immediately after needling, the distal tip of the XEN stent was freed and connected to a cystic space with significant IOP reduction. The third patient suffered from abrupt bleb flattening on the 5^th postoperative day following XEN stent implantation. AS-OCT revealed internal occlusion of the XEN stent with exudative material, which resolved spontaneously after intensifying topical steroids with improved bleb functioning 2 days later. AS-OCT provides in-depth microscopic evaluation of the XEN stent and its relationship with surrounding tissue. This information is helpful in identifying causes of impaired outflow, determining the timing, and effect of needling intervention in eyes with inadequate bleb functioning or IOP control, especially during the early postoperative period.

Preparing the ocular surface for glaucoma filtration surgery: an unmet clinical need

The mutual relationship among medical therapy, ocular surface (OS) and filtration surgery (FS) represents one of the most crucial issues in glaucoma management. As the long-term use of intraocular pressure-lowering medications significantly affect the OS health, patients with an uncontrolled disease frequently undergo glaucoma surgery in less-than-ideal conditions. As we known, OS changes strongly affect the post-operative bleb filtration capability. Therefore, improving the OS conditions before proceeding with FS is needed. Currently, given the rapid diffusion of new surgical procedures, this need is even more perceived. Nevertheless, despite surgeons retain the OS preparation of primary importance, and recognize the OS disease (OSD) as the only modifiable risk factor for filtration failure, there is no agreement on which strategies should be preferred to prepare patients. This is largely due to the lack of validated guidelines, which forces clinicians to adopt personal approaches based on evidence derived from low-quality studies. In this review, we provided an overview of risk factors involved in the FS failure, with particular attention to those depending on OS changes, and how OSD negatively affects the aqueous humor resorption after surgery. Moreover, we reported the most exploited measures to mitigate the OSD before surgery, the possible reasons underlying the absence of shared approaches, and the upcoming area of intervention to preserve the OS health during glaucoma management. Finally, based on the current evidence, we proposed a pre-operative outline reporting the main risk factors that should be considered before surgery, and the therapeutical options available to improve the OS.

Outcomes of XEN45 gel stent using posterior small incision sub-tenon ab interno insertion (Semi-open) technique

PURPOSE

To evaluate the 12-month outcomes of a novel posterior small incision sub-tenon ab interno technique of XEN stent insertion ('Semi-open').

METHOD

Consecutive eyes underwent XEN stent insertion with the Semi-open technique by two surgeons between 1st July 2018 and 30th September 2019. All cases received subconjunctival injection of 0.1 mL of mitomycin C 0.2 mg/mL. Eyes with primary open angle glaucoma (OAG), secondary OAG or pseudophakic primary angle closure glaucoma (PACG) were included. Exclusion criteria were phakic PACG, uveitic or neovascular glaucoma and postoperative follow-up <12 months. Primary outcomes were defined by World Glaucoma Association guidelines. Secondary outcomes included change in glaucoma medications, needling rates and complications.

RESULTS

We included 37 consecutive eyes of 35 patients with primary OAG (n = 30), secondary OAG (n = 6) and pseudophakic PACG (n = 1). Thirty-one eyes (84%) received a standalone XEN implantation and 6 (16%) underwent XEN implantation combined with phacoemulsification. The IOP reduced from 19.6 ± 6.0 mmHg preoperatively to 11.2 ± 2.6 mmHg at 12 months (P < 0.01). The number of glaucoma agents reduced from 3.49 ± 1.14 preoperatively to 1.57 ± 1.36 at 12 months. At 12 months, qualified success was 97.3% and complete success was 32%, with one case requiring trabeculectomy. Needling was required in 19% of cases over the 12 month follow up. Complications included 19 cases of transient hypotony and 7 cases of transient choroidal effusion. There were no cases of exposure, bleb leak or bleb-related infection.

CONCLUSION

Semi-open XEN technique achieves high surgical success rate in the medium-term with relatively low post-operative bleb needling rate.

Primary Needling of the Ab Interno Gelatin Microstent Reduces Postoperative Needling and Follow-up Requirements

PURPOSE

To evaluate the effect of primary needling at the time of ab interno gelatin microstent insertion on postoperative needling rates.

DESIGN

Retrospective, interventional cohort study.

PARTICIPANTS

Eighty-six eyes of 74 patients with no prior incisional surgery.

METHODS

Consecutive eyes with open-angle glaucoma refractory to medical treatment that underwent ab interno gelatin microstent insertion (XEN; Allergan Inc.) with or without primary needling.

MAIN OUTCOME MEASURES

Primary outcome measure was the proportion of eyes requiring postoperative needling. Secondary outcome measures included the mean reduction in intraocular pressure (IOP), topical glaucoma medication use, complications, reoperations, and number of follow-up clinic visits over 12 months.

RESULTS

Fifty-one eyes (42 patients, median age 74 years) underwent XEN surgery with primary needling at the time of surgery, and 35 eyes (32 patients, median age 73 years) underwent XEN surgery without routine primary needling. Eyes that received routine primary needling had an 84.8% lower rate of postoperative needling (3.9% vs. 25.7%, P = 0.003) and required fewer postoperative clinic visits (P = 0.043). Median IOP was 18.0 mmHg (interquartile range [IQR], 13.0-23.0) on 3.0 (IQR, 2.0-3.0) classes of topical medications at baseline. At 12 months, the median IOP was 11.0 mmHg (IQR, 9.0-14.0) in the primary needling group and 11 mmHg (IQR, 10.0-14.0) when primary needling was not routinely performed. Both groups demonstrated a high safety profile. In total, 5 eyes required further glaucoma surgery with insertion of a glaucoma drainage device.

CONCLUSIONS

Primary needling at the time of XEN gel stent insertion is associated with a significant reduction in the need for postoperative needling and postoperative clinic visits. This modification provides a predictable postoperative course with a significant and sustained reduction in both IOP and glaucoma medication requirements with less intense postoperative management.

Ab-Externo Implantation of XEN Gel Stent for Refractory Steroid-Induced Glaucoma After Lamellar Keratoplasty

The hazy corneal donor-recipient interface after corneal transplant may cause difficulties when implanting the XEN gel stent via ab-interno approach. We aim to describe XEN gel stent implantation via ab-externo approach in refractory steroid-induced glaucoma after corneal lamellar keratoplasty. Under local anaesthesia, the XEN injector needle was inserted 7 mm behind the limbus with the bevel facing up, directly beneath the conjunctiva and advanced to the marked 2.5 mm scleral entry wound. The needle then pierced the sclera until the needle tip was just visible in the anterior chamber (AC). The slider was pushed until the tip of the XEN stent was seen in the AC. The needle was slowly withdrawn while still pushing the slider to complete stent deployment. Subconjunctival Mitomycin C 0.01% (30 µg/0.3 mL) was then injected posterior to the bleb. Three eyes of three patients with steroid-induced glaucoma after lamellar keratoplasty underwent XEN gel stent implantation via ab-externo approach placed at the superotemporal quadrant. Pre-operatively, all patients had uncontrolled IOP between 30-45 mmHg despite maximum medications and selective laser trabeculoplasty. After XEN gel stent implantation, IOP ranged between 10-17 mmHg with one or two topical antiglaucoma at 12 months. Complications include hypotony maculopathy, stent migration and hyphaema, all of which were successfully managed. Corneal graft remained clear at 12 months. XEN gel stent implantation via ab-externo approach is able to achieve good intraocular pressure (IOP) control without compromising cornea graft in patients with steroid-induced glaucoma after lamellar keratoplasty at 12 months.

[Preoperative management of subconjunctival/sub-Tenon's glaucoma surgery with special consideration of the gel implant (XEN®)]

BACKGROUND

When using subconjunctival/sub-Tenon's ab interno glaucoma surgical procedures, patient selection and preoperative management are essential to reduce postoperative scarring of the bleb.

OBJECTIVE

The aim of this study was to compile a list of risk factors that may have an unfavorable effect on the scarring process.

METHOD

A literature search was carried out in PubMed with respect to the scarring process of the gel implant XEN®.

RESULTS

Ophthalmological risk factors for conjunctivoscleral/Tenon's wound healing process include dry eye, allergies, use of eye drops containing preservatives and previous eye surgery.

CONCLUSION

The preoperative administration of artificial tear substitutes, corticosteroids and the fundamental change to preservative-free eye drops can support the normalization of a chronic inflammatory altered conjunctiva and thus positively influence the wound healing process after surgery.

XEN 63 gel stent device in glaucoma surgery: A 5-years follow-up prospective study

PURPOSE

To evaluate the efficacy and safety of the XEN63 Gel Stent in patients with open-angle glaucoma (OAG).

METHODS

Prospective, nonrandomized, open-label, not-controlled, and single center study conducted on OAG patients who underwent glaucoma surgery with the XEN63 gel stent. The main outcome measure was intraocular pressure (IOP). Secondary end-points were number of topical ocular hypotensive drugs, percentage of patients achieving an IOP reduction ⩾20%, and treatment-related adverse events.

RESULTS

Eleven eyes from 11 patients were treated with XEN 63. Mean (95% confidence interval, CI) age was 78.8 (73.7-85.9). Two eyes (18.2%) underwent XEN alone, while nine eyes (81.8%) underwent combined XEN + cataract extraction (phacoemulsification). The median (95% CI) IOP reduction was 17.7% (-13.3% to 34.9%). At the end of the study 9 (81.8%) eyes had an IOP ⩽ 18 mm Hg, six of them without treatment. Six (54.6%) eyes obtained an IOP reduction ⩾20%. Compared to baseline, there was a significant reduction in the number of ocular hypotensive drugs (p = 0.0039). There were no treatment-related serious adverse events. Early postoperative complications included diplopia (1), blood in endothelium (2), ocular hypertension (1), corneal edema (1), folds in Descemet's membrane (1), and contact between the implant and the iris (1). All the adverse events were successfully solved without sequalae. One eye required bleb needling.

CONCLUSION

The XEN63 implant significantly reduced both IOP and the amount of ocular hypotensive medications while maintaining a good safety profile.

Surgical Approaches for Implanting Xen Gel Stent without Conjunctival Dissection

The XEN Gel Stent (Allergan Inc., an Abbvie company) is an implant that lowers intraocular pressure by creating a filtration pathway from the anterior chamber to the subconjunctival space, using the same pathway as trabeculectomy. While the primary method for implantation is via ab interno approach, it is also possible to implant the device ab externo. This technique paper details the surgical steps for closed conjunctival implantation of the Gel Stent and provides surgical pearls for enhancing outcomes.

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Cataract and glaucoma combined surgery: XEN® gel stent versus nonpenetrating deep sclerectomy, a pilot study

Background

To compare the efficacy of phacoemulsification (PKE) combined with nonpenetrating deep sclerectomy (NPDS) with mitomycin C (MMC) versus XEN® gel stent with MMC.

Methods

In this nonrandomized, retrospective, comparative, single-center pilot study, 105 consecutive eyes of 75 patients with uncontrolled primary open-angle glaucoma (POAG) and cataract who underwent PKE combined with either XEN implantation (n = 47) or NPDS (n = 58) between May 2013 and November 2018 were included. The primary outcome was complete success at 9 months, which was defined as intraocular pressure (IOP) ≤18, 15 or 12 mmHg without treatment; qualified success was IOP ≤18, 15 or 12 mmHg with antiglaucoma medications. Secondary outcome measures included the number of antiglaucoma medications, visual acuity (VA), and postoperative adverse events.

Results

Using the 18 mmHg threshold, complete or qualified success was achieved in 69.6 and 89.1% in the PKE + XEN group, and 63.8 and 89.7% in the PKE + NPDS group (p = .54 and p = .93), respectively, at 9 months. The mean IOP decreased from 20.8 ± 6.8 mmHg to 16.2 ± 2.8 mmHg in the PKE + XEN group (p < .001, 18.9% mean drop), and from 21.5 ± 8.9 mmHg to 14.9 ± 3.9 mmHg in the PKE + NPDS group (p < .001, 25.6% mean drop). Best-corrected VA significantly improved (p < .001) in both groups. The mean number of antiglaucoma medications was significantly reduced from 2.66 ± 1.1 to 0.49 ± 1.0 in the PKE + XEN group (p < .001) and from 2.93 ± 0.9 to 0.69 ± 1.2 in the PKE + NPDS group (p < .001).

Conclusions

The XEN stent combined with PKE seemed to be as effective and safe as PKE + NPDS at 9 months in this pilot study.

Technique of Xen Implant Revision Surgery and the Surgical Outcomes: A Retrospective Interventional Case Series

Purpose

The Xen® Gel Stent (Allergan, Irvine, CA, USA) is a minimally invasive glaucoma surgery device implanted to reduce intra-ocular pressure (IOP) in glaucoma. The stents can fail to drain post-operatively due to scarring of the conjunctiva around the stent opening. Data on the success rates of revision surgery in patients with Xen stent failure are scarce. We present the first detailed report of the steps, outcomes and complications of Xen revision surgery with 12 months of follow-up data.

Methods

We share our experiences on the circumstances in which to perform Xen revision surgery, the steps of the surgery and the results of a retrospective interventional case series of all Xen revisions performed at a single centre from 2013 to 2018.

Results

A total of 151 Xen implants were inserted into eyes at our tertiary centre during the study period, of which 21 eyes (patients) underwent revision surgery. Mean pre-operative IOP was 26.1 (standard deviation 8.3) mmHg with the patient on two drops of anti-glaucoma medication. Four patients were excluded from the analysis due to incomplete data (medical records were unavailable for 2 patients; 1 patient died shortly after surgery; and 1 patient moved to another area). A non-functioning Xen implant was identified in another patient during revision surgery, and the procedure was converted to a trabeculectomy. The remaining 16 patients were included in the analysis, all of whom had a minimum follow-up of 12 months, with the longest follow-up being 4 years following revision surgery. Of these 16 patients, four required needling and 5-fluorouracil injection in the first 12 months following revision surgery, three required further glaucoma drainage surgery due to the failure of the revision surgery to control IOP in the first year and one suffered bleb-related endophthalmitis at the site of previous trabeculectomy surgery. Mean IOP at 12 months following revision surgery was 16.3 (standard deviation 3.7) mmHg on 0.7 drops of anti-glaucoma medication, which equates to a 37.5% reduction in IOP and a 65% reduction in the amount of IOP-lowering drops required.

Conclusion

Our study shares experience on when to perform Xen revision surgery and the steps required. The results of our small cohort are the first in the literature and show that revisions can achieve promising IOP and medication reductions. Some patients still require needling in the post-operative period to optimise outcomes.

Two-year results of a multicenter study of the ab interno gelatin implant in medically uncontrolled primary open-angle glaucoma

PURPOSE

To evaluate the effectiveness of an ab interno subconjunctival gelatin implant as primary surgical intervention in reducing intraocular pressure (IOP) and IOP-lowering medication count in medically uncontrolled moderate primary open-angle glaucoma (POAG).

METHODS

In this prospective, non-randomized, open-label, multicenter, 2-year study, eyes with medicated baseline IOP 18-33 mmHg on 1-4 topical medications were implanted with (phaco + implant) or without (implant alone) phacoemulsification. Changes in mean IOP and medication count at months 12 (primary outcomes) and 24, clinical success rate (eyes [%] achieving ≥ 20% IOP reduction from baseline on the same or fewer medications without glaucoma-related secondary surgical intervention), intraoperative complications, and postoperative adverse events were assessed.

RESULTS

The modified intent-to-treat population included 202 eyes (of 218 implanted). Changes (standard deviation) in mean IOP and medication count from baseline were - 6.5 (5.3) mmHg and - 1.7 (1.3) at month 12 and - 6.2 (4.9) mmHg and - 1.5 (1.4) at month 24, respectively (all P < 0.001). Mean medicated baseline IOP was reduced from 21.4 (3.6) to 14.9 (4.5) mmHg at 12 months and 15.2 (4.2) mmHg at 24 months, with similar results in both treatment groups. The clinical success rate was 67.6% at 12 months and 65.8% at 24 months. Overall, 51.1 (12 months) and 44.7% (24 months) of eyes were medication-free. The implant safety profile compared favorably with that published for trabeculectomy and tube shunts.

CONCLUSIONS

The gelatin implant effectively reduced IOP and medication needs over 2 years in POAG uncontrolled medically, with an acceptable safety profile. ClinicalTrials.gov registration number: NCT02006693 (registered in the USA).

Migration of XEN45 Implant: Findings, Mechanism, and Management

Aim

The aim of this study is to report the mechanism of XEN migration and its management.

Background

Over the past decade, new less invasive surgical approaches for glaucoma have been devised and carried out successfully. One such technique is the use of the XEN gel stent. We present a rare and relatively unknown complication of XEN migration and present in detail the likely mechanism by which this occurs, and its subsequent management.

Case description

A 73-year-old male with primary angle closure on maximal medical treatment presented with an intraocular pressure of 30 mm Hg in the left eye. The visual acuity was 6/5, iridocorneal angles were open in all four quadrants, and the cup disc ratio was 0.4. As phacoemulsification alone was unlikely to adequately lower intraocular pressures, the patient underwent combined phacoemulsification and XEN implantation. Although the patient had a good postoperative result with pressures lowered to 11 mm Hg, 4 months after the operation, the XEN was found to have migrated 4 mm into the anterior chamber, associated with a low-grade uveitis. The patient subsequently had the XEN explanted a new XEN inserted. Pressures lowered 1 month postoperatively to 14 mm Hg.

Conclusion

XEN migration is likely due to a combination of mechanical and frictional forces. If the XEN is positioned such that more than 2 mm is in the subconjunctival space, the XEN is likely to be angled upward and, therefore, be more susceptible to these forces and undergo migration.

Clinical significance

It is essential that XEN implants are correctly sited and that this is confirmed intraoperatively to prevent the need for further procedures.

How to cite this article

Ali ZC, Khoo DI, et al. Migration of XEN45 Implant: Findings, Mechanism, and Management. J Curr Glaucoma Pract 2019;13(2):79–81.