Effect of the outer stent position on efficacy after minimally invasive transscleral glaucoma gel stent implantation

Long-term Outcomes of PreserFlo MicroShunt versus XEN45 Gel Stent in Open-Angle Glaucoma

PURPOSE

To compare two glaucoma drainage devices with subconjunctival filtration (MicroShunt and XEN) for open-angle glaucoma (OAG), with respect to effectiveness and safety.

PATIENTS AND METHODS

This is a single center, retrospective, interventional study. In total, 106 eyes of 95 patients with OAG underwent surgery. Of these patients, 51 eyes of 45 patients received a MicroShunt implantation and 55 eyes of 50 patients received an XEN implantation. Failure was defined as an intraocular pressure (IOP) lower than 5 or higher than 17 mmHg at the end of follow-up after 2 years, the need for surgical revision, secondary glaucoma surgery, or loss of light perception. Outcome was rated as complete success or qualified success, depending on whether it was achieved with or without anti-glaucomatous medications. Postoperative complications and interventions were also documented for both groups.

RESULTS

In the MicroShunt group, mean IOP decreased from 20.6 ± 7.5 mmHg at baseline to 13.0 ± 3.9 mmHg (p < 0.0001) after 2 years. In the XEN group, mean IOP was lowered from 22.5 ± 7.9 mmHg to 13.5 ± 4.2 mmHg (p < 0.0001). In both groups, the mean number of medications was significantly reduced (MicroShunt 2.7 ± 1.2 to 0.9 ± 2.5; p < 0.0001 vs. XEN 3.2 ± 0.9 to 1.1 ± 1.5; p < 0.0001). In regard to success rates, 37% of MicroShunt patients achieved complete success and 57% qualified success at the end of follow-up. In the XEN group, rates were 25 and 45%, respectively. Patient demographics differed between the two groups with respect to age (MicroShunt 72.8 ± 8.7 vs. XEN 67.7 ± 9.0 years; p = 0.002). Postoperative complications were comparable between the two groups.

CONCLUSION

Both MicroShunt and XEN are effective in significantly reducing IOP and glaucoma medications in OAG, and with a good safety profile.

[Glaucoma Filtration Surgery - Bleb-forming Procedures]

Glaucoma filtration surgery has been a standard surgical therapy for decades. An increasing knowledge about wound healing processes in the eye, the introduction of antimetabolite treatment and continuous improvements of the surgical technique helped making trabeculectomy - the prototype filtration surgery - a very effective therapeutic tool. However, best results will only be regularly achieved with a high level of experience and time dedicated to postoperative follow-up. Furthermore, the potential for severe early and late complications still remains high. Thus, novel stent-based filtration surgery approaches, such as the Preserflo and the XEN shunt have been introduced. This review presents these three bleb-forming filtration procedures, covering the basic principles of surgical technique, data on effectivity as well as complications.

Three-year clinical outcome of XEN45 Gel Stent implantation versus trabeculectomy in patients with open angle glaucoma

OBJECTIVE

To reliably compare the three-year clinical outcome and safety of XEN45 Gel Stent implantation (XEN) vs. trabeculectomy (TRAB) in patients with glaucoma.

SUBJECT/METHODS

We conducted a retrospective cohort study with patients with primary open angle or pseudoexfoliation glaucoma with uncontrolled intraocular pressure (IOP) undergoing XEN or TRAB at the Innsbruck University Clinic of Ophthalmology and Optometry, Austria and analysed changes in IOP, numbers of IOP-lowering medications, and complete surgical success (i.e., IOP ≤ 18 mmHg, ≥20% IOP reduction and not requiring IOP-lowering medication) up to 36 months postoperatively.

RESULTS

Between 2013 and 2019, we performed XEN Gel Stent implantation in 58 eyes and trabeculectomy in 84 eyes. From baseline to 36 months, mean IOP decreased from 23.4 to 13.8 mmHg (mean reduction 35%, 95% confidence interval 23-48%, p < 0.001) in the XEN group and from 25.1 to 11.2 mmHg (mean reduction 50%, 41-60%, p < 0.001) in the TRAB group. TRAB provided higher IOP reduction than XEN Gel Stent implantation at 12, 24, and 36 months (all p < 0.05). In XEN versus TRAB, IOP-lowering medication was required by 98.3% vs. 97.6% before surgery (p = 0.781), differed significantly at month 12 (43.2% vs. 2.0%, p < 0.001)but not at month 24 or 36. Complete surgical success was achieved in 40.0% vs. 62.8% at month 24 (adjusted odds ratio 2.70; 1.04-7.00, p = 0.040) and 27.3% vs. 56.8% at month 36 (4.36; 1.25-15.18, p = 0.021).

CONCLUSION

Compared to XEN, TRAB was associated with lower intraocular pressure, less IOP-lowering medication, and higher probability of achieving complete surgical success over a 36-month follow-up period.

Matched case-control comparison of surgical success after XEN45 Gel Stent and PRESERFLO MicroShunt implantation in a Caucasian population

BACKGROUND

The aim of this study was to compare the outcome of implantation of a XEN45 Gel Stent with the outcome of implantation of a Preserflo MicroShunt in a matched-pair analysis in eyes being naïve to filtering surgery.

METHODS

In this comparative, retrospective study, 50 eyes that had undergone XEN45 Gel Stent implantation were compared with 50 eyes after Preserflo implantation. Follow-up was at least 6 months, and surgical success was measured by criteria A (IOP < 21 mmHg, IOP reduction >20%, no repeat surgery); criteria B (IOP < 18 mmHg, IOP reduction >20%, no repeat surgery); and criteria C (IOP ≤15 mmHg, IOP reduction ≥40%, no repeat surgery).

RESULTS

After a follow-up period of 12 months, mean IOP had decreased from preoperative 25.2 ± 4.8 mmHg in the XEN group to 14.5 ± 4.0 (n = 35) and from 25.3 ± 6.8 mmHg to 11.9 ± 2.9 (n = 41) in the Preserflo group, respectively. The IOP at the last follow-up of the two groups differed significantly (p < 0.01). The probability of surgical success did not differ concerning Criteria A and B, but surgical success was significantly higher in the Preserflo group for Criteria C (60%, p < 0.01).

CONCLUSION

Both the Preserflo and XEN45 Gel Stent provide an effective and safe treatment option for advanced glaucoma and have a high potential to reduce intraocular pressure. Absolute IOP levels of <16 mmHg after 12 months were significantly more frequent in the Preserflo group.

Minimally Invasive Glaucoma Surgery: Latest Developments and Future Challenges

The development of minimally invasive glaucoma surgeries (MIGSs) was intended to provide safe and modestly efficacious modalities for early intervention of mild-to-moderate glaucoma, with minimal trauma and rapid recovery. They were mainly ab interno procedures that reduce intraocular pressure by facilitating the aqueous outflow by bypassing the trabecular meshwork resistance, reinforcing the uveoscleral flow via the supraciliary space, and reducing aqueous production by the ciliary body. While the cumulating evidence helps shape the role of the available MIGS, the exponential new development and advancement in this field has expanded the territory of MIGS. Apart from developing subconjunctival MIGS filtration devices (Xen gel stent and PRESERFLO MicroShunt), there is a tendency to revisit the "traditional" MIGS for alternative use and to modify the procedures with consideration of the fundamental aqueous outflow physiology. Combined MIGS has also been suggested, based on the theory that their different mechanisms may provide additive or synergistic effects. The advancement of laser procedures is also promising and could supplement unmet needs along the glaucoma treatment algorithm. This review examines the broad array of MIGS, updates the recent findings, discusses their potential alternative applications, and explores future challenges.

[Comparison of new and old procedures in glaucoma surgery : Trabeculectomy, Preserflo and XEN]

Glaucoma is one of the most frequent causes of irreversible blindness worldwide. The main risk factor of the disease is an individually too high intraocular pressure and pressure reduction is still the only established treatment. If conservative pressure reduction and adherence are insufficient, and if the patient is unable to tolerate conservative treatment, surgical procedures become necessary. There are nowadays more than a dozen different surgical procedures for lowering the pressure. This article presents and discusses the procedures that have a subconjunctival pre-equatorial drainage in common. These include trabeculectomy, the XEN-gel implant and the Preserflo microshunt.

Bleb-related Porcine Lymphatic Outflow is Greater from Subconjunctival compared to Subtenon Blebs

Aim

Understanding the mechanism of fluid outflow by comparing the subconjunctival and subtenon spaces can lead to improved ocular therapeutics. The purpose of the current study is to evaluate subconjunctival vs subtenon lymphatic outflow by creating tracer-filled blebs in each location.

Methods

Porcine (n = 20) eyes received subconjunctival or subtenon injection(s) of fixable and fluorescent dextrans. Blebs were angiographically imaged using a Heidelberg Spectralis ([Heidelberg Retina Angiograph] HRA + OCT; Heidelberg Engineering) and bleb-related lymphatic outflow pathways were counted. Optical coherence tomography (OCT) imaging of these pathways was used to assess structural lumens and the presence of valve-like structures. Furthermore, a comparison between tracer injection locations (superior/inferior/temporal/nasal) was made. Histologic analyses for subconjunctival and subtenon outflow pathways were performed, to confirm tracer co-localization with molecular lymphatic markers.

Results

Subconjunctival blebs demonstrated a greater number of lymphatic outflow pathways compared to subtenon blebs in every quadrant [superior: 6.10 ± 1.18 (subconjunctival) vs 0.50 ± 0.27 (subtenon); temporal: 2.30 ± 0.40 vs 0.10 ± 0.10; nasal: 5.30 ± 0.60 vs 0.30 ± 0.21; inferior: 6.00 ±1.29 vs 0.1 ± 0.1; all comparisons p < 0.001]. For subconjunctival blebs, the temporal quadrant showed fewer lymphatic outflow pathways compared to the nasal side (p = 0.005).

Discussion

Subconjunctival blebs accessed greater lymphatic outflow compared to subtenon blebs. Furthermore, regional differences existed, with fewer lymphatic vessels temporal than at the other locations.

Clinical significance

Aqueous humor drainage after glaucoma surgery is incompletely understood. The present manuscript adds to our understanding of how lymphatics might influence filtration bleb function.

How to cite this article

Lee JY, Strohmaier CA, Akiyama G, et al. Bleb-related Porcine Lymphatic Outflow Is Greater from Subconjunctival compared to Subtenon Blebs. J Curr Glaucoma Pract 2022;16(3):144-151.

The efficacy of XEN gel stent implantation in glaucoma: a systematic review and meta-analysis

Background

Xen is a device for minimally invasive glaucoma surgery, and is used to treat POAG, pseudoexfoliative or pigmentary glaucoma, as well as refractory glaucoma. The efficacy of XEN in treating glaucoma remains to be confirmed and clarified. Hence, we conducted a systematic review and meta-analysis to examine the efficacy and associated complication of XEN implantations.

Methods

We conducted a literature search in PubMed, EMBASE, the Cochrane Library of Systematic Reviews, Web of Science, China National Knowledge Infrastructure, WanFang and SinoMed databases to identify studies, published before May 15, 2021, which evaluated XEN in glaucoma, and parameters for measurements included intra-ocular pressure (IOP), number of anti-glaucoma medications (NOAM), and bleb needling rate. We compared the measurements of XEN-only procedure between phaco-XEN and trabeculectomy, and we also did sub-analysis based on time points, glaucoma types, ethnics, etc. Sensitivity analyses and publication bias were conducted for evaluating bias.This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA 2020) reporting guideline.

Results

We identified 78 eligible studies, analysis revealed obvious IOP reduction after XEN stent implantation (SMD: 1.69, 95% CI 1.52 to 1.86, p value < 0.001) and NOAM reduction (SMD: 2.11, 95% CI 1.84 to 2.38, p value < 0.001). Sub-analysis showed no significant difference with respect to time points, ethnicities, and economic status. No significant difference was found between XEN treatment effect on POAG and PEXG eyes and between pseudo-phakic and phakic eyes. Also no significant difference was found between XEN and phaco-XEN surgery in terms of IOP after surgery (SMD: -0.01, 95% CI -0.09 to 0.08, p value 0.894). However, NOAM (after publication bias correction) and bleb needling rate (RR: 1.45, 95% CI 1.06to 1.99, p value 0.019) were lower in phaco-XEN group compared to XEN only group. Compared to trabeculectomy, XEN implantation had similar after-surgery IOP, however bleb needling rate (RR: 2.42, 95% CI 1.33 to 4.43, p value 0.004) was higher.

Conclusion

Our results confirmed that XEN is effective in lowering both IOP and NOAM till 48 months after surgery. It is noteworthy that XEN implantation leads to higher needling rate, compared to phaco-XEN or trabeculectomy. Further research, studying complications of XEN on non-European ethnicities, especially on Asian, are in urgent need before XEN is widely applied.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02502-y.

Anterior Segment-Optical Coherence Tomography Bleb Morphology Comparison in Minimally Invasive Glaucoma Surgery: XEN Gel Stent vs. PreserFlo MicroShunt

Background: The purpose of this study is to compare the morphology of six-month follow-up blebs created by a subconjunctival glaucoma surgical device (XEN45) to those created by a PreserFlo MicroShunt with a sub-Tenon insertion, utilizing AS-OCT. Methods: A retrospective study of 29 eyes who underwent XEN45 implantation and 29 eyes who underwent PreserFlo MicroShunt implantation. The patients were analyzed at 24 h, 1 week, 1 month, 3 months and 6 months. At each visit, the maturation and morphological alterations of the blebs were observed, as well as connections with the IOP. Results: In both groups, IOP showed significant reduction at all follow ups (p < 0.0001). In XEN group, the most common bleb morphology in the immediate postoperative was the subconjuntival separation type (42%) followed by the uniform type (34%), with a trend inversion at 6 month follow up (51% of uniform type). On the contrary, the most common morphology after PreserFlo was the multiple internal layer (55%), which showed a tendency to reduce over time and was substituted by the microcystic multiform, whose percentage increased over time (17% at day 1 vs. 44% at month 6). Uniform appearance was associated by the posterior episcleral fluid (PEF) lake presence. Both horizontal and vertical diameters significantly increased over time. Conclusion: XEN and PreserFlo implantation resulted in the production of diffuse blebs with different characteristics, which may influence IOP lowering capacity and bleb revisions necessity over time.

Anterior segment imaging in minimally invasive glaucoma surgery - A systematic review

Minimally invasive glaucoma surgery (MIGS) has grown in popularity over the past decade. This systematic review explores the peri-operative and intraoperative application of anterior segment imaging to maximize the efficacy and safety of MIGS. A review of the PubMed, EMBASE and CINAHL databases was conducted, with inclusion criteria restricted to MIGS that had received United States Food and Drug Administration (FDA) premarket approval, FDA 510(K) premarket notification, or were listed as a class 1 device exempt from FDA approval or notification. 21 manuscripts from 21 unique studies were identified pertaining to MIGS devices including the XEN Gel Stent, Trabectome, iStent Inject, 1st-generation iStent and the Kahook Dual Blade (KDB). Anterior segment imaging modalities included anterior segment optical coherence tomography (AS-OCT), ultrasound biomicroscopy (UBM), aqueous angiography, OCT volumetric scans and in vivo confocal microscopy. Identification and evaluation of aqueous outflow pathways before and after MIGS have potential for improving patient preoperative patient selection and postoperative outcomes. Intraoperative imaging potentially provides the resolution needed for good visualization of angle anatomy and accurate evaluation of surgical endpoints in angle-based MIGS. Anterior segment imaging has been used to identify procedural complications, provide objective information on implant location in relation to surrounding anatomy, assess the post-implantation structural impact of MIGS devices and manage bleb failure and scarring. Technical difficulties in incorporating imaging modalities into the surgical microscope, variable quality of images and optical interference from ocular structures or surgical instruments are remaining barriers, which discourage the widespread clinical use of this technology.

Three-year effectiveness and safety of the XEN gel stent as a solo procedure or in combination with phacoemulsification in open-angle glaucoma: a multicentre study

Purpose

To assess the 3‐year effectiveness and safety of the XEN gel stent implanted ab interno in open‐angle glaucoma (OAG).

Methods

This study was a multicentre, retrospective chart review of consecutive patients with OAG who underwent ab‐interno gel stent placement alone or combined with phacoemulsification between 1 January 2014 and 1 October 2015. Outcome measures included mean changes in intraocular pressure (IOP) and IOP‐lowering medication count from medicated baseline at 1, 2, 3 (primary outcome) and 4 years (if available) postimplantation. Intraoperative complications, adverse events of special interest (AESIs) and secondary surgical interventions (SSIs) were recorded.

Results

The safety and effectiveness populations included 212 eyes (primary and secondary) and 174 eyes (primary), respectively. Mean IOP and medication decreased from 20.7 mmHg and 2.5 at baseline (n = 163 primary/first implanted eyes) to 13.9 mmHg and 1.1 medications (n = 76) at 3 years postimplantation, respectively. Mean changes from baseline in IOP (−5.6, −6.2 and −6.6 mmHg) and IOP‐lowering medication count (−1.8, −1.6 and −1.4) were statistically significant at 1, 2 and 3 years postimplantation, respectively. Results appeared comparable when implantation was performed with (n = 76) or without (n = 98) phacoemulsification. In primary eyes with 4‐year IOP and medication count data (n = 27), mean IOP was 14.0 mmHg on 1.3 medications at 4 years postimplantation. Fifteen (7.1%) eyes had intraoperative complications, 31 (14.6%) experienced 46 postoperative AESIs, and 26 (12.3%) required SSI.

Conclusion

The gel stent effectively lowered IOP and IOP‐lowering medication count over 3 years, with a predictable and acceptable safety profile, when implanted via the traditional ab‐interno technique.

Bleb Analysis Using Anterior Segment Optical Coherence Tomography and Surgical Predictors of XEN Gel Stent

Purpose

To determine the early predictors of surgical success 6 months after XEN surgery among clinical parameters, including anterior segment optical coherence tomography (AS-OCT).

Methods

A total of 31 eyes with medically uncontrolled primary open-angle glaucoma or pseudoexfoliation glaucoma was enrolled retrospectively. Using AS-OCT, XEN tip location was categorized into intraconjunctival, intratenon, or uviform at day 1 and blebs were classified into no or low, high sparse, high thick, cystic, or mixed walls at month 6. Using slit-lamp photography, blebs were classified into no or low, localized avascular, diffuse avascular, localized vascular, or diffuse vascular blebs at month 6. Surgical success was defined as an intraocular pressure (IOP) of less than 14 mm Hg.

Results

Intraconjunctival and intratenon locations of the tip mostly created a high sparse wall, whereas the uviform type mostly created no or low wall and no or low bleb. The uviform type was linked to pseudoexfoliation glaucoma. A high sparse wall and diffuse avascular bleb showed a lower mean IOP than a high thick wall and localized vascular bleb. In the multivariate analysis, female sex and IOP at week 1 were early predictors of surgical success (8.45 times and 33.1% per 1 mm Hg-decrease, respectively).

Conclusions

Bleb evaluation using AS-OCT is valuable to correlate tip location and bleb morphology with clinical profiles, considering that a lower early postoperative IOP is linked to surgical success.

Translational Relevance

Bleb analysis using AS-OCT on day 1 could help to predict bleb morphology after 6 months, which is important to maintain the functioning bleb in the longer term.

Anterior-segment optical coherence tomography of filtering blebs in the early postoperative period of ab externo SIBS microshunt implantation with mitomycin C: Morphological analysis and correlation with intraocular pressure reduction

PURPOSE

To analyse the morphological evolution of filtering blebs with anterior-segment OCT (AS-OCT) and its correlation with intraocular pressure after ab externo SIBS microshunt implantation with mitomycin C (MMC) during a 3-month follow-up period.

METHODS

Twenty-eight filtering blebs of 28 patients with open-angle glaucoma were measured horizontally and vertically in the sub-Tenon space with AS-OCT after ab externo SIBS microshunt implantation with MMC. The intraocular pressure (IOP) was monitored simultaneously at each visit. Maturation of and morphological changes in the blebs and correlations with the IOP were recorded.

RESULTS

The average median preoperative IOP of 20.7 (range, 12-30) mmHg decreased to 8.5 (range, 4-17), 8.9 (range, 5-17), 10.4 (range, 8-16) and 10.9 (range, 9-15) mmHg at 24 hr, 1 week, 1 month and 3 months, respectively (p < 0.001). A multiform morphology on AS-OCT prevailed at all time points, with a 3.5% rate of a uniform bleb morphology at the first week. The horizontal and vertical diameters of the blebs increased from baseline to the third month. The horizontal expansion (406 ± 127 μm on day 7, p = 0.04, 712 ± 211 μm on day 30, p = 0.02 and 952 ± 218 μm on day 90, p < 0.001) was greater than the vertical expansion (16 ± 18 μm, p = 0.3 on day 1, 63 ± 27 μm, p = 0.02 on day 30 and 137 ± 34 μm, p < 0.001 on day 90) without correlation with the IOP (r = -0.3, p = 0.2).

CONCLUSION

Anterior-segment OCT (AS-OCT) of the filtering blebs formed after ab externo SIBS microshunt implantation showed progressive horizontal and vertical expansion of the blebs in the sub-Tenon space, with a significant peak at the first month not significantly correlated with the decrease in the IOP.

Evaluation of the Ultrastructural and In Vitro Flow Properties of the PRESERFLO MicroShunt

Purpose

To measure the in vitro flow properties of the PRESERFLO implant for comparison with the theoretical resistance to flow.

Methods

The PRESERFLO was designed to control the flow of aqueous humor according to the Hagen-Poiseuille (HP) equation. Scanning electron microscopy (SEM) was performed to analyze the ultrastructure, and flow measurements were carried out using a gravity-flow setup.

Results

SEM images of the PRESERFLO showed luminal diameters of 67.73 × 65.95 µm and 63.66 × 70.54 µm. The total diameter was 337.2 µm, and the wall was 154 µm wide. The theoretical calculation of the resistance to flow (R) for an aqueous humor (AH) viscosity of 0.7185 centipoises (cP) was 1.3 mm Hg/(µL/min). Hence, assuming a constant AH flow of 2 µL/min, the pressure differential across the device (ΔP) was estimated to be 2.6 mm Hg. The gravity-flow experiment allowed us to measure the experimental resistance to flow, which was R_E = 1.301 mm Hg/(µL/min), in agreement with the theoretical resistance to flow R given by the HP equation.

Conclusions

The experimental and theoretical flow testing showed that the pressure drop across this device would not be large enough to avoid hypotony unless the resistance to outflow of the sub-Tenon space was sufficient to control the intraocular pressure in the early postoperative period.

Translational Relevance

The fluid properties of glaucoma subconjunctival drainage devices determine their specific bleb-forming capacity and ability to avoid hypotony and therefore their safety and efficacy profile.

Open Conjunctival Approach for Sub-Tenon's Xen Gel Stent Placement and Bleb Morphology by Anterior Segment Optical Coherence Tomography

PRCIS

Sub-Tenon's implantation of the Xen Gel stent resulted in significant intraocular pressure (IOP) lowering along with a low rate of postoperative bleb needling, and a favorable bleb morphology on anterior segment optical coherence tomography (AS-OCT).

PURPOSE

The aim was to assess clinical outcomes and bleb morphology following sub-Tenon's implantation of the Xen Gel Stent.

METHODS

The medical records of patients who underwent sub-Tenon's Xen Gel Stent implantation with intraoperative mitomycin-C through an open conjunctival approach were reviewed. Postoperative IOP and number of glaucoma medications at 1, 3, 6, 9, and 12 months were assessed. Bleb morphology was analyzed at various timepoints using AS-OCT (Topcon DRI OCT version 1.1.1).

RESULTS

Twenty-six eyes were included in the study. Mean age was 69.4±8.0 years. Mean preoperative IOP was 28.1±7.8 mm Hg on an average of 3.5±0.9 glaucoma medications. Mean IOP at postoperative month 12 (n=23 eyes) was 12.9±4.0 mm Hg (P<0.01) on an average of 0.3±0.6 (P<0.01) glaucoma medications. Three eyes (12%) required postoperative needle revision. Bleb morphology in the early postoperative period (≤3 mo) was characterized by multiple small subconjunctival microcysts on AS-OCT. At the intermediate (6 to 12 mo) and long-term (>12 mo) timepoints, reduction in microcysts with multiple internal parallel layers of aqueous flow and a uniform pattern were more frequently noted. All functional blebs were characterized by the presence of a posterior episcleral fluid lake. Failed blebs showed absence of aqueous humor around the distal end of the microshunt.

CONCLUSION

Following an open conjunctival approach, sub-Tenon's placement of the Xen Gel Stent with significant IOP lowering was achieved. In eyes with good shunt function, bleb morphology by AS-OCT showed a posterior episcleral fluid lake similar to findings following trabeculectomy.

Late-onset Endophthalmitis after XEN45® Implantation: A Retrospective Case Series and Literature Review

AIM AND OBJECTIVE

To report the incidence of late-onset endophthalmitis following XEN45® stent implantation.

BACKGROUND

Long-term safety profile and efficacy in relation to the so-called microinvasive glaucoma surgery (MIGS) techniques are still under evaluation. The XEN45® gel stent entails a bleb formation and often requires postoperative conjunctival management, differing from the current reviewed concept of minimally invasive procedures. Endophthalmitis has been described among the complications, triggered in the majority of cases by tube extrusion.

CASES DESCRIPTION

From our chart of 293 eyes operated on between November 2016 and November 2019, five (1.7%) patients developed endophthalmitis, which took place in the months 3, 4, 5, 11, and 14 after surgery, respectively. Sixty percent had undergone previous needling procedures. All of them showed a previous flat bleb and developed perforation of the conjunctiva caused by the distal portion of the tube. One patient was early eviscerated due to a fateful course. Treatment consisted of intravitreal, oral, and topical antibiotics, as well as topical corticosteroids. Eighty percent underwent device withdrawal, conjunctival gap suturing, anterior chamber washout, aqueous humor (AH) tab extraction (one positive for S. epidermidis and one for Streptococcus agalactiae), and pars plana vitrectomy. A second patient was eviscerated due to phthisis bulbi. Out of three remaining patients, one underwent vitrectomy for retinal detachment, while two patients required glaucoma surgery for intraocular pressure control. The final VA was ≤20/125 in all patients.

CONCLUSION

The XEN45® device appears to trigger endophthalmitis by extruding the stent or unnoticed leakage through conjunctival defects. Special attention should be paid to flat and avascular blebs.

CLINICAL SIGNIFICANCE

This series shows a higher rate of endophthalmitis (1.7%) compared with previous studies with a significant sample size (0.4-1.4%).

HOW TO CITE THIS ARTICLE

Burggraaf-Sánchez de las Matas R, Such-Irusta L, Alfonso-Muñoz EA, et al. Late-onset Endophthalmitis after XEN45® Implantation: A Retrospective Case Series and Literature Review. J Curr Glaucoma Pract 2021;15(3):153-160.

PreserFlo MicroShunt® exposure: a case series

BACKGROUND

PreserFlo® MicroShunt (PM) (also known as InnFocus® MicroShunt) is a subconjunctival stent implanted ab externo via a minimally invasive surgical procedure. The current indication is progressive, mild to moderate, open angle glaucoma uncontrolled on topical medications. According to the literature, adverse events are rare, mild and transient.

CASE PRESENTATION

Two cases of stand-alone PreserFlo MicroShunt® implantation in patients with uncontrolled open-angle glaucoma are reported. Exposure occurred 7 days and 3 months respectively after implantation. These cases shared common features including preexisting blepharitis and the lack of a Tenon's flap. In both cases, removal of the device was required after several attempts at repair.

CONCLUSIONS

PreserFlo MicroShunt® exposure is a potentially vision-threatening complication because of the risk of endophthalmitis. Potential risk factors include the absence of a Tenon's flap and pre-existing ocular surface inflammation. Ocular surface inflammation should be detected and treated prior to PM implantation. If a deficiency in Tenon's capsule is noted intraoperatively, close monitoring should be performed because of the higher risk of PM exposure.

[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.

Safety and efficacy of bilateral simultaneous XEN implant surgery: a pilot study

OBJECTIVE

To evaluate the efficacy and safety of the bilateral simultaneous XEN (BISIXEN) surgery in open-angle glaucoma patients.

METHODS

Retrospective analysis of a prospective data base conducted on uncontrolled glaucoma patients who underwent BISIXEN surgery. Primary endpoint measure was the incidence of sight-threatening complications. Secondary endpoints included intraocular pressure (IOP) reduction and in number of required antiglaucoma medications.

RESULTS

Ten patients (20 eyes) were included in the analysis. Median (95% confidence interval) follow-up was 12.0 (7.0-12.0) months, with 14 eyes having a follow-up of 12 months. No sight-threatening complications, such as endophthalmitis, retinal detachment, corneal decompensation, or intraocular hemorrhages were observed in any eye of study sample. Mean IOP decreased significantly from 25.2 (21.5-28.9) mm Hg at baseline to 15.1 (13.4-16.8) mm Hg at the last follow-up visit (p = 0.0001). Mean number of antiglaucoma medications was significantly reduced from 2.9 (2.5 to 3.3) drugs at baseline to 0.40 (0.00-0.70) at the end of the study (p < 0.0001). At the last study visit, 14 (70.0%) eyes had an IOP ≥ 6 and ≤ 18 mm Hg without treatment. Two eyes needed surgical revision and three ones needed a new glaucoma surgery: two underwent Ahmed valves (one eye with aniridia and the other previously operated on) and one underwent non-penetrating deep sclerectomy.

CONCLUSIONS

Bilateral simultaneous XEN implantation may be a feasible strategy in those patients with high anesthetic risk.

XEN45 Gel Stent implantation in eyes with primary open angle glaucoma: A study from a single hospital in Taiwan

BACKGROUND

To evaluate the effectiveness and safety of the XEN45 Gel Stent in East Asian patients with primary open angle glaucoma (POAG).

METHODS

We retrospectively reviewed 37 medically uncontrolled POAG patients who received XEN45 Gel Stent. The primary outcomes were reduction in intraocular pressure (IOP) and in the number of glaucoma medications 12 months after surgery. The secondary outcomes were requirement for intervention and further glaucoma surgery. The adverse intraoperative and postoperative events were investigated.

RESULTS

At the 12-month postoperative follow-up, the mean IOP was significantly reduced from the preoperative value of 21.7 ± 7.7 mmHg to 15.0 ± 2.0 mmHg (p = 0.001). The mean number of glaucoma medications decreased from 3.4 ± 0.9 to 1.3 ± 1.5 (p < 0.001). Seventeen patients (45.9%) required postoperative interventions. Four patients (10.8%) received additional glaucoma surgery. Postoperative IOP at month 1 was significantly associated with outcomes at the 12-month follow-up and the need for subsequent intervention and additional glaucoma surgery.

CONCLUSION

The XEN45 Gel Stent effectively reduced the IOP values and number of glaucoma medications in East Asian patients with POAG. No major complications were observed, but almost half of the eyes in the study required intervention for wound healing modification. Postoperative IOP at month 1 was a predictor of surgical success at 12 months after surgery.

[Endophthalmitis after perforation of the conjunctiva by a glaucoma gel-stent implant]

Intraokulare Infektionen durch Abiotrophia defectiva sind sehr selten. Hier berichten wir von einer 57-jährigen Patientin, welche sich 3 Monate nach erfolgter komplikationsloser Kataraktoperation mit Implantation eines Glaukom-Gelstents am rechten Auge mit einer Abiotrophia-defectiva-assoziierten Endophthalmitis bei uns vorstellte. Die Patientin klagte zuvor über eine Rötung im Bereich der nasal oberen Bindehaut des rechten Auges sowie über Schmerzen 2 Wochen vor Auftreten der Endophthalmitis. Eine 2‑wöchige topische Steroidtherapie ohne Antibiotikaschutz brachte eine kurzfristige Besserung. Die Patientin stellte sich nun bei uns mit einem Hypopyon, einer akuten Visusverschlechterung und starken periokulären Schmerzen seit dem frühen Morgen vor. Der Gelstent hatte spontan die Konjunktiva perforiert. Es erfolgte die unmittelbare Therapie mit lokaler und systemischer Antibiose. Sechs Stunden danach wurde eine Pars-plana-Vitrektomie mit intraokularer Gabe von Antibiotika durchgeführt. Durch eine zeitnahe Therapie konnte in diesem Fall ein relativ benigner Verlauf erreicht werden. Im klinischen Alltag sollte bei Patienten, die sich nach glaukomchirurgischen Eingriffen mit akuter Visusverschlechterung und Schmerzen präsentieren, dringend an eine mögliche spontane Bindehautperforation und Late-onset-Endophthalmitis gedacht werden. Zudem ist zu empfehlen, dass eine unklare Konjunktivitis nach Glaukomchirurgie immer antibiotisch abgedeckt und engmaschiger kontrolliert werden sollte.

Learning Curve and One-Year Outcome of XEN 45 Gel Stent Implantation in a Swedish Population

Purpose

Evaluation of 1-year-outcome of XEN 45 gel stent surgery in a Swedish cohort with regard to clinical success, complications, and learning curve.

Patients and Methods

This was a retrospective study of glaucoma patients undergoing glaucoma XEN-stent surgery alone or combined with phacoemulsification between December 2015 and May 2017. Intraocular pressure (IOP), number of medical agents, and adverse events were assessed. Clinical success rate was defined as achieving individual target pressure with/without medication.

Results

A total of 113 eyes were included in the final statistics. Mean age was 70.8±11.8 years. Primary open angle glaucoma (POAG) accounted for 46.9% and exfoliative glaucoma (PEXG) for 40.7%. Mean preoperative IOP was 23.8±6.2 mmHg and mean number of agents 3.4. After 1 year, mean IOP was reduced to 16.1±4.7 mmHg and medication to 1.34 substances on average. Failure rate at 1-year follow-up was 34% with no significant difference between POAG and PEXG. There was a trend of higher success rate for combined cases (P=0.116). Stents with malpositioned or curved appearance had significantly worse outcome. The failure rate of the most productive surgeon dropped from 33% to 10% from the first implantations. Temporary hypotony (19.5%) and choroidal detachment (9.7%) were the most common complications. Blockage of the inner stent lumen was common (8.8%), with a high proportion of failure.

Conclusion

XEN-stent surgery is a surgical option in uncontrolled glaucoma in both POAG and PEXG. A XEN-stent can reduce both IOP and the number of antiglaucoma medications needed. The learning curve is significant and stent positioning is crucial for optimal results. Combined XEN-cataract surgery is not inferior to stand-alone procedures. The long-time effectiveness is still to be proven.

Effective treatment of a normal-tension glaucoma patient with bilateral ab externo XEN Gel Stent implantation

Purpose

To provide the first report of effective use of bilateral XEN Gel Stent implantation using an ab externo open-conjunctival approach designed to improve bleb function and meet the uniquely low intraocular pressure requirements of a Japanese patient with normal-tension glaucoma refractory to topical medical therapy.

Observations

A 54-year-old phakic Japanese woman with severe normal-tension glaucoma on maximally tolerated medical therapy of four topical agents presented with above-goal intraocular pressures and new medication intolerances. She underwent bilateral ab externo open-conjunctival XEN Gel Stent implantation with tenectomy and sub-Tenon's injection of 40μg of mitomycin-C, which resulted in reduction of intraocular pressures by 41.2 and 28.6% to 10 and 10 mmHg in the right and left eyes, respectively at the most recent visit. Postoperatively, a diffuse filtering bleb with good morphology developed in both eyes. The procedure has so far allowed for complete cessation of all four topical medications for up to eight months following surgery without any serious complications.

Conclusions

This case illustrates the potential of Xen Gel Stent implantation through an ab externo, open-conjunctival approach to be an effective, simple alternative to trabeculectomy to meet the unique low-pressure requirements of normal-tension glaucoma patients with practical and safety benefits of a micro-invasive approach.

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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XEN® Gel Stent: A Comprehensive Review on Its Use as a Treatment Option for Refractory Glaucoma

The XEN Gel Microstent is a subconjunctival microinvasive glaucoma surgical device developed with the aim of improving the predictability and safety profile of bleb-forming glaucoma surgical procedures. The stent is a hydrophilic tube composed of a porcine gel cross-linked with glutaraldehyde with good stability and biocompatibility with minimal tissue reaction. This device has demonstrated promising outcomes with fewer risks compared to traditional surgeries. The aim of the review is to present early studies on different designs of the XEN Gel Stent, to summarize different surgical techniques of implantation and to analyze more comprehensively the results, complications and rates of needling of the commercially available device (Xen 45). The review will address separately special cases (PXG, UVG, ICE, congenital glaucoma) and describe small series and case reports.

Personalising surgical treatments for glaucoma patients

Surgical treatments for glaucoma have relied for decades on traditional filtering surgery such as trabeculectomy and, in more challenging cases, tubes. Antifibrotics were introduced to improve surgical success in patients at increased risk of failure but have been shown to be linked to a greater incidence of complications, some being potentially vision-threatening. As our understanding of glaucoma and its early diagnosis have improved, a more individualised management has been suggested. Recently the term "precision medicine" has emerged as a new concept of an individualised approach to disease management incorporating a wide range of individual data in the choice of therapeutic modalities. For glaucoma surgery, this involves evaluation of the right timing, individual risk factors, targeting the correct anatomical and functional outflow pathways and appropriate prevention of scarring. As a consequence, there is an obvious need for better knowledge of anatomical and functional pathways and for more individualised surgical approaches with new, less invasive and safer techniques allowing for earlier intervention. With the recent advent of minimally invasive glaucoma surgery (MIGS) a large number of novel devices have been introduced targeting potential new sites of the outflow pathway for lowering intraocular pressure (IOP). Their popularity is growing in view of the relative surgical simplicity and apparent lack of serious side effects. However, these new surgical techniques are still in an era of early experiences, short follow-up and lack of evidence of their superiority in safety and cost-effectiveness over the traditional methods. Each year several new devices are introduced while others are withdrawn from the market. Glaucoma continues to be the primary cause of irreversible blindness worldwide and access to safe and efficacious treatment is a serious problem, particularly in the emerging world where the burden of glaucoma-related blindness is important and concerning. Early diagnosis, individualised treatment and, very importantly, safe surgical management should be the hallmarks of glaucoma treatment. However, there is still need for a better understanding of the disease, its onset and progression, the functional and structural elements of the outflow pathways in relation to the new devices as well as their long-term IOP-lowering efficacy and safety. This review discusses current knowledge and the future need for personalised glaucoma surgery.

Lamellar sclerectomy augmented XEN gel stent glaucoma surgery

PURPOSE

To describe a surgical technique to optimize XEN gel stent position and its outflow.

METHODS

A small 1- to 1.5-mm square lamellar sclerectomy was created at the external tip of the XEN gel stent implant. The lamellar scleral tissue, served as a patch graft, was secured at the gel stent insertion site.

RESULTS

Four sequential, unselected, patients with failed primary XEN gel stent surgeries underwent bleb revisions with the technique described. These four patients achieved unmedicated intraocular pressures between 10 and 12 mmHg and a favourable bleb morphology despite repeated mitomycin C applications at 6 months.

CONCLUSION

Lamellar sclerectomy with auto-scleral graft augmented XEN gel stent surgery deliver successful short-term outcomes without major complications observed.