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

PRESERFLO™ MicroShunt as a treatment option for highly increased intraocular pressure in primary open angle glaucoma and pseudoexfoliation glaucoma

PURPOSE

The Preserflo-MicroShunt (PF) is an established device for treating glaucoma, effectively reducing intraocular pressure (IOP) with a good safety record. However, its efficacy in eyes with significantly elevated preoperative IOP levels is not well-documented due to exclusion from many clinical studies. This study aims to evaluate PF outcomes in eyes with highly increased IOP and compare them with those having moderately increased levels.

METHODS

Retrospectively, eyes diagnosed with primary open angle glaucoma (POAG) or pseudoexfoliation glaucoma (PXG) undergoing PF were analysed. They were categorized into two groups: highly increased IOP (HI-IOP, ≥30 mmHg) and moderately increased IOP (MI-IOP, ≤25 mmHg). IOP, number of IOP lowering medications (NoM), success rates (SR), and postoperative complications were compared at 1, 3, 6, and 12 months.

RESULTS

One year postoperatively, IOP was reduced from 39.0 ± 7.4 mmHg to 14.4 ± 4.4 mmHg in the HI-IOP and from 19.5 ± 3.6 mmHg to 14.0 ± 4.5 mmHg in the MI-IOP group. NoM decreased significantly in both groups (p < 0.001 for all). Success rates did not differ between groups during the first year (p > 0.05 in all subgroups). However, the HI- IOP group had higher rates of persistent hypotony (7% vs. 0%, p = 0.02) and tendentially higher rates of choroidal detachment (23% vs. 11%, p = 0.08). Other adverse events were rare and comparable. Further glaucoma surgery was required in 26% and 19% of cases, respectively (p = 0.41).

CONCLUSION

PF appears to be a suitable option for managing both highly and moderately increased IOP levels in POAG and PXG eyes, with comparable outcomes up to 12 months following surgery.

Risk factors and protective strategies for hypotony following preserflo microshunt implantation

The PreserFlo MicroShunt (PMS) is a minimally invasive surgical device for glaucoma management. However, postoperative hypotony remains a significant complication. This retrospective cohort study analyzed 471 eyes to evaluate the efficacy of PMS implantation in reducing intraocular pressure (IOP) and medication dependency, as well as to identify risk factors associated with hypotony. The median IOP decreased significantly from 19 mmHg preoperatively to 10 mmHg three months postoperatively, with the median medications score dropping to zero. Postoperative hypotony occurred in 18.7% of the cases. Multivariate analysis identified preoperative IOP ≥ 25 mmHg (odds ratio (OR): 2.01, 95% confidence interval (CI): 1.00-4.02, p = 0.049) and medication scores ≥ 5 (OR: 2.12, 95% CI: 1.13-3.96, p = 0.019) as significant risk factors for hypotony, while axial length ≥ 25.5 mm (OR: 0.19, 95% CI: 0.09-0.39, p < 0.001) and intraluminal suture stenting (OR: 0.08, 95% CI: 0.03-0.25, p < 0.001) were significantly protective. Importantly, intraluminal suture stenting mitigated the risk of hypotony without compromising the short-term surgical outcomes. These findings emphasize the need for careful patient selection and the potential of intraluminal suture stenting as an effective intraoperative strategy to improve the safety and outcomes of PMS implantation.

Update on Surgical Techniques Best Practices to Optimize Outcomes Following Gel Stent Implantation

The XEN®45 Glaucoma Treatment System (gel stent; Allergan, an AbbVie company, Irvine, CA, USA) is a minimally invasive bleb-forming surgical device that was originally approved to lower intraocular pressure by diverting the aqueous humor from the anterior chamber to the subconjunctival space (like trabeculectomy) following ab-interno placement. Since approval of the gel stent in multiple countries, the implantation technique has evolved considerably, being performed ab interno or ab externo with open or closed conjunctiva, based on patients' needs and/or surgeons' preferences. Additional technical variations that can facilitate gel stent placement and/or improve outcomes have also emerged. This article aims to increase awareness of these developments to facilitate informed decision-making and improve surgical success and outcomes for patients.

The use of intraluminal PRESERFLO stenting in avoiding early postoperative hypotony

PURPOSE

Postoperative hypotony following PRESERFLO MicroShunt (PMS) implantation is a frequent cause of complications such as choroidal detachment and hypotony maculopathy. This study aims at evaluating the impact of intraluminal stenting of the PMS during the early postoperative period.

METHODS

We retrospectively analyzed the data of 97 patients who underwent PMS implantation with intraoperative placement of a Nylon 10-0 suture as intraluminal stent (PStent) and compared the outcomes to those of an existing database of the traditional MicroShunt implantation technique (PTrad, n = 120). The primary outcome measure was the intraocular pressure (IOP) at one week postoperatively. As a secondary outcome measure, adverse hypotony, defined as an IOP ≤ 5 mmHg with significant choroidal effusion and/or anterior chamber shallowing or the presence of macular folds was also assessed. Additionally, the time to stent removal and the IOP one week after stent removal were reported.

RESULTS

Preoperative median IOP was 25.0 (20.5-30.3) mmHg in PStent and 25.0 (19.3-32.0) mmHg in PTrad (p = 0.62). One week after surgery, the median IOP dropped to 10.0 (8.0-13.0) mmHg in PStent and 7.0 (5.0-9.0) in PTrad (p < 0.01). At one month, the IOP was 12.0 (10.0-14.0) mmHg in PStent and 10.0 (8.0-11.0) mmHg in PTrad (p < 0.01). After 3 months, both groups showed similar median IOP levels of 11.0 (8.0-13.5) mmHg and 10.0 (9.75-13.0) mmHg in PStent and PTrad, respectively (p = 0.66). The presence of adverse hypotony was significantly lower in PStent compared to PTrad (6.2% vs 15.8%, p < 0.05). In PStent the stent was removed after 30.0 (21.0-42.5) days. One week after stent removal the mean IOP drop was 6.1 ± 0.5 mmHg (p < 0.01).

CONCLUSION

In the early follow-up period, intraluminal stenting of the PMS appears to be safe and effective in controlling the IOP while reducing early postoperative hypotony. Surgical success is not compromised by stent placement. Based on our data, it is recommended to remove the suture two to six weeks after surgery for most patients with uncomplicated postoperative clinical findings.

Flow characterization and structural alterations in Ahmed glaucoma FP7 tubes after in-vitro aging in silicone oil

PURPOSE

Patients with intraocular silicone oil (SO) display higher odds of surgical failure after Ahmed glaucoma valve (AGV) implantation compared to patients without SO. However, the structural impact of SO exposure on silicone-made AGV tubes and the resulting changes in flow rate remain unexplored. This in-vitro study evaluated changes in tube dimensions and flow rates of AGV FP7 tubes after SO exposure to inform clinicians how such changes may impact AGV functionality.

METHODS

AGV FP7 tube segments underwent accelerated aging to approximate 90 days of exposure to the following media: Balanced Salt Solution (BSS), 1000 centistokes (cs) SO, and 5000cs SO. Tube dimensions were measured before and after aging. A constant gravity flow test setup was created to measure flow rates through tubes before and after aging. The students' T-test was used to compare the mean change between groups post-aging.

RESULTS

Post-exposure, 1000cs and 5000cs SO tube segments increased in length by 5.94% and 5.55%, respectively, compared to 0.38% of BSS tubes (P < 0.05 for both). The inner lumen area expanded for tube segments in 1000cs and 5000cs SO by 11.75% and 2.70%, respectively, but contracted for tubes in BSS by -2.70% (P < 0.01 and P = 0.068 for 1000cs and 5000cs SO, respectively). Post aging, the flow rates increased on average by 61.0% and 98.6% for 1000cs and 5000cs SO, respectively, whereas flow rates for BSS tube segments slightly decreased by -4.92%. The difference was statistically significant for BSS vs. SO groups (P < 0.01 for both).

CONCLUSIONS

Prolonged exposure to SO structurally altered the AGV FP7 tube segments by expanding their cross-sectional area, potentially leading to increased flow rates. These results may inform clinicians about potential in-vivo interactions in patients with the simultaneous presence of glaucoma drainage devices and intraocular SO.

Intermediate-term impact on corneal endothelial cells and efficacy of Preserflo MicroShunt implantation in patients with open-angle glaucoma - a prospective study over two years

INTRODUCTION

Preserflo MicroShunt is a novel microinvasive bleb forming device for the treatment of primary open-angle glaucoma. The intermediate- and long-term success and the impact of this procedure on corneal endothelial cell density remain to be investigated.

METHODS

In this prospective observational study, 62 eyes of 55 glaucoma patients (mean age ± SD: 67.0 ± 15.0 years) receiving a Preserflo MicroShunt were included. Corneal endothelial cell density, intraocular pressure and best corrected visual acuity were assessed preoperatively and at 3, 6, 9, 12, 18 and 24 months postoperatively. Success rates, bleb revision rates and complications were analysed. Complete success was defined as an intraocular pressure reduction of ≥ 20% and achieving a target pressure of ≤ 18, ≤ 15 or ≤ 12 mmHg without antiglaucoma medication. Qualified success indicated that the criteria were reached with or without medication.

RESULTS

Corneal endothelial cells showed no significant decline over 24 months (p > 0.05). Intraocular pressure showed a substantial reduction postoperatively (p < 0.001), decreasing from 29.6 ± 8,3 mmHg to 13.0 ± 4.3 mmHg after 24 months (p < 0.001). Complete and qualified success with a target pressure ≤ 15 mmHg was achieved in 52.9% and 54.6% of cases after 24 months, respectively. Best corrected visual acuity did not change after 24 months.

CONCLUSION

Preserflo MicroShunt had no negative side effects on corneal endothelial cells and showed favourable success rates after 2 years in patients with open-angle glaucoma.

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.

PRESERFLO MicroShunt in Severe Myopia: A Case Report and Review of the Literature

The PRESERFLO™ MicroShunt (MP; Santen Inc., Osaka, Japan) is a minimally invasive bleb surgery (MIBS) manufactured to treat primary open-angle glaucoma (POAG), with lower postoperative adverse effects than with conventional filtering surgeries. We describe here the case study of a 58-year-old woman who presented with bilateral severe myopia with bilateral advanced POAG and unreached target pressure under quadritherapy, who was successfully managed by PM surgery. A review of the literature completes our observation. At presentation, the patient had a spherical equivalent of - 7.50 RE and - 7.75 LE with an IOP of 22 mmHg right and left eye (RLE) under quadritherapy, and with severe bilateral visual field loss, including scotomas within the central 5°. The patient presented with systemic hypertension treated with an antihypertensive drug. Two selective laser trabeculoplasties (SLT), performed 3 months apart, were first tried on the LE, without any change in IOP at 2 months. After considering the high risk of postoperative complications, a PM operation was proposed, with a targeted IOP in the mid-fifteens RLE. The patient's eyes underwent PM surgery with mitomycin C (MMC) MMC0.2 mg/mL for 3 minutes without any complications. The LE required 2 consecutive needlings with 1 mL MMC0.2 mg/mL. At 24 months after surgery, the two eyes gave successful results without the need for any additional medical therapy, and with well-functioning conjunctival blebs. The PM was an effective alternative to the gold standard trabeculectomy in our severely myopic patient. A comparative study between conventional filtering operations and this MIBS in highly myopic patients would confirm our observation.

The Development of a SIBS Shunt to Treat Glaucoma

Many pharmaceutical and medical device start-up companies share similar goals. Each experience is different and offers important lessons for companies seeking Food and Drug Administration approval. This article offers important advice for budding entrepreneurs as it discusses some career-altering decisions, lessons learned in the start-up world, the technology leading up to innovation, the relevant science, medicine, chemistry, and engineering, the need to develop novel biomaterials, the regulatory path, and the business process culminating in the development of a Poly(styrene-block-isobutylene-block-Styrene)-based microshunt to treat glaucoma that led to the founding of InnFocus, Inc. (Miami, FL) in 2004, and then the acquisition of InnFocus by Santen Pharmaceuticals (Osaka, Japan) in 2016.

A simple surgical solution for the treatment of persistent postoperative hypotony after PRESERFLO MicroShunt implantation

BACKGROUND/OBJECTIVES

PRESERFLO MicroShunt implantation is a relatively new and increasingly popular treatment for recalcitrant glaucoma. Though relatively uncommon, persistent or severe postoperative hypotony may occur and its treatment presents a significant challenge.

SUBJECTS/METHODS

Interventional case series of the first 7 consecutive patients who underwent the insertion of a rip-cord suture to treat severe or persistent postoperative hypotony.

RESULTS

In 6 patients, the hypotony resolved and vision was restored. The 7th patient had suffered a severe suprachoroidal haemorrhage with a poor visual recovery and limited follow-up, so success was more difficult to assess.

CONCLUSIONS

Stenting the PRESERFLO MicroShunt with a rip-cord suture is a simple technique to correct persistent or severe postoperative hypotony.

Bleb geometry and morphology after Preserflo Microshunt surgery: Risk factors for surgical failure

PURPOSE

To investigate the possible risk factors for treatment failure in patients who had undergone Preserflo Microshunt (PMS) implantation, using anterior-segment optical coherence tomography (AS-OCT) to analyze the internal structures of the bleb.

METHODS

The PMS blebs of 54 patients were evaluated with AS-OCT. A mathematical model was used to calculate the total filtering surface of the episcleral fluid cavity (EFC) and the hydraulic conductivity (HC) of the bleb wall. Complete and qualified success were defined as IOP between 6 and 17 mmHg with or without glaucoma medication. The relation between baseline characteristics and probability of bleb success was analyzed by bivariate and multivariate logistic regression. The main outcome measures were mean bleb wall thickness (BWT), reflectivity (BWR), HC, mean horizontal and vertical diameter and total filtering surface (TFS) of the EFC.

RESULTS

Blebs from 74% patients were considered as complete success and 26% as failure. BWR and BWT increased linearly up to the first year in both groups. BWR was higher in the group failure (p = 0.02) and BWT in the group success (p<0.001). EFC was wider and shorter in the success group (p = 0.009, p = 0.03). Higher TFS showed a negative correlation with IOP (r = -0.4, p = 0.002). Higher baseline IOP was associated with success of PMS by multivariate analysis (p = 0.01). Mean HC, 0.034 ± 0.008 (μL/min)/mm2/mmHg, was negatively correlated with bleb surface (r = -0.5, p<0.0001) and wall´s thickness (r = -0.3, p = 0.01).

CONCLUSIONS

AS-OCT revealed that successful PMS blebs could show either thick hyporreflective walls or wide filtering surfaces with thin capsules. A higher baseline IOP increased the probability of surgical success.

Systematic Preserflo MicroShunt Intraluminal Stenting for Hypotony Prevention in Highly Myopic Patients: A Comparative Study

Transient hypotony is the most common early complication after Preserflo MicroShunt (PMS) implantation. High myopia is a risk factor for the development of postoperative hypotony-related complications; therefore, it is advisable that PMS implantation in patients should be performed while employing hypotony preventive measures. The aim of this study is to compare the frequency of postoperative hypotony and hypotony-related complications in high-risk myopic patients after PMS implantation with and without intraluminal 10.0 nylon suture stenting. This is a retrospective, case-control, comparative study of 42 eyes with primary open-angle glaucoma (POAG) and severe myopia that underwent PMS implantation. A total of 21 eyes underwent a non-stented PMS implantation (nsPMS), while in the remaining eyes (21 eyes), PMS was implanted with an intraluminal suture (isPMS group). Hypotony occurred in six (28.57%) eyes in the nsPMS group and none in the isPMS group. Choroidal detachment occurred in three eyes in the nsPMS group; two of them were associated with the shallow anterior chamber and one was associated with macular folds. At 6 months after surgery, the mean IOP was 12.1 ± 3.16 mmHg and 13.43 ± 5.22 mmHg (p = 0.41) in the nsPMS and isPMS group, respectively. PMS intraluminal stenting is an effective measure to prevent early postoperative hypotony in POAG highly myopic patients.

A model for designing intraocular pressure-regulating glaucoma implants

Glaucoma is a group of eye conditions that damage the optic nerve, the health of which is vital for vision. The key risk factor for the development and progression of this disease is increased intraocular pressure (IOP). Implantable glaucoma drainage devices have been developed to divert aqueous humor from the glaucomatous eye as a means of reducing IOP. The artificial drainage pathway created by these devices drives the fluid into a filtering bleb. The long-term success of filtration surgery is dictated by the proper functioning of the bleb and overlying Tenon’s and conjunctival tissue. To better understand the influence of the health condition of these tissues on IOP, we have developed a mathematical model of fluid production in the eye, its removal from the anterior chamber by a particular glaucoma implant–the PRESERFLO^® MicroShunt–, drainage into the bleb and absorption by the subconjunctival vasculature. The mathematical model was numerically solved by commercial FEM package COMSOL. Our numerical results of IOP for different postoperative conditions are consistent with the available evidence on IOP outcomes after the implantation of this device. To obtain insight into the adjustments in the implant’s hydrodynamic resistance that are required for IOP control when hypotony or bleb scarring due to tissue fibrosis take place, we have simulated the flow through a microshunt with an adjustable lumen diameter. Our findings show that increasing the hydrodynamic resistance of the microshunt by reducing the lumen diameter, can effectively help to prevent hypotony. However, decreasing the hydrodynamic resistance of the implant will not sufficiently decrease the IOP to acceptable levels when the bleb is encapsulated due to tissue fibrosis. Therefore, to effectively reduce IOP, the adjustable glaucoma implant should be combined with a means of reducing fibrosis. The results reported herein may provide guidelines to support the design of future glaucoma implants with adjustable hydrodynamic resistances.

Efficacy and Safety of the Preserflo Microshunt With Mitomycin C for the Treatment of Open Angle Glaucoma

PRCIS

The Preserflo Microshunt (PSM) is a safe and effective glaucoma microfiltering implant that significantly reduces the intraocular pressure (IOP), either alone or in combination with phacoemulsification, during the first year after surgery.

PURPOSE

The purpose of this study was to assess the safety and efficacy of the PSM for the treatment of open angle glaucoma with 0.2 mg/mL mitomycin C, either alone or in combination with cataract surgery.

METHODS

A retrospective, open-label study of 64 eyes with primary open angle glaucoma that underwent PSM implantation and were followed up for at least 9 months. Success was defined as IOP 6-17 mm Hg and a reduction of at least 20%, complete without hypotensive medication, and qualified with medication. Safety was assessed by the incidence of adverse events. Secondary endpoints included mean hypotensive medications, visual acuity, and incidence of needling and surgical revision.

RESULTS

A total of 51 eyes underwent PSM alone and 13 underwent PSM+phacoemulsification. In the overall population of the study, the mean IOP was significantly reduced from 22.03±0.7 mm Hg at baseline to 12.7±0.4 mm Hg at the final visit, P <0.0001 (mean follow-up: 11±1.4 mo). The IOP was significantly reduced in both groups ( P <0.0001). Ocular hypotensive medication was reduced significantly from 2.7±0.7 to 0.2±0.5 ( P <0.0001). No significant differences were found in IOP-lowering medication between groups (PSM alone, 0.2±0.08; PSM+phacoemulsification, 0.1±0.1; P =0.2). At the final visit, 70.3% were considered as complete success and 12.5% as qualified success. The most common adverse event was clinical hypotony (7.8%) followed by hyphema (4.7%), and anterior chamber reformation (1.6%). Overall, 1.6% required needling and 15.6% surgical revision to restore the flow.

CONCLUSION

Glaucoma surgery with the PSM and mitomycin C was efficacious and safe in the short term, either alone or in combination with cataract surgery, and may be considered a surgical option for lowering IOP in primary open angle glaucoma.

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.

PreserFlo® MicroShunt: An Overview of This Minimally Invasive Device for Open-Angle Glaucoma

For moderate-to-severe glaucoma, trabeculectomy remains the “gold standard” intraocular pressure (IOP)-lowering treatment; nonetheless, this method requires extensive post-operative maintenance. Microinvasive glaucoma surgery (MIGS) treatments are designed to lessen intra- and post-operative care burden while offering an acceptable IOP decrease for individuals with mild to moderate glaucoma. The PreserFlo® MicroShunt (previously InnFocus MicroShunt) is an 8.5 mm glaucoma drainage device manufactured from poly(styrene-block-isobutylene-block-styrene) (SIBS), an extremely biocompatible and bioinert material. The lumen is narrow enough to prevent hypotony, but big enough to avoid being obstructed by sloughed cells or pigment. The device is implanted ab externo, as a stand-alone procedure or in conjunction with cataract surgery, with intraoperative mitomycin C, and a bleb is produced under the conjunctiva and Tenon’s capsule. The MicroShunt was CE-marked in 2012 and designed for primary open-angle glaucoma, the IOP of which remains uncontrolled after maximally tolerated topical treatment. Several clinical trials evaluating the MicroShunt’s long-term safety and effectiveness have been conducted, highlighting the effectiveness of the device over time, along with a tolerable safety profile. The present review aims to gather evidence of PreserFlo’s effectiveness and safety results almost 10 years after its introduction, and furthermore, to compare it with other MIGS and with the gold-standard trabeculectomy for glaucoma management.