Clinicopathologic correlations of poly-(styrene-b-isobutylene-b-styrene) glaucoma drainage devices of different internal diameters in rabbits

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 bleb surgery versus minimally invasive glaucoma surgery: a 12-month retrospective study

This study aimed to compare the IOP-lowering effectiveness and safety of standalone Preserflo MicroShunt and iStent 1st generation implantation combined with phacoemulsification in Caucasian patients with a 12-month follow-up period. This retrospective study analyzed the medical histories of patients undergoing antiglaucoma surgery at the Department of Ophthalmology, Medical University of Bialystok, between January 2019 and January 2022. The main outcome measures were success rates (complete: proportion of eyes with IOP < 18 mmHg (criterion A) and < 15 mmHg (criterion B) or 20% reduction in IOP without any glaucoma medication; qualified: proportion of eyes achieving IOPs < 18 mmHg and < 15 mmHg or 20% reduction in IOP from baseline with or without medications), mean reduction (%) in IOP, medication burden, number of complications and additional interventions. In both groups, a significant decrease in IOP and medication burden were observed at 6 and 12 months when compared with baseline. At 12 months, qualified surgical success in criterion A was recorded in 67.4% and 85.7% of patients in the Preserfo and iStent groups, respectively (p = 0.045). Complete surgical success in criterion B at 12 months accounted to 61.4% of patients from Prserflo group and 32.7% patients in iStent group (p = 0.04). Surgical failure at 12 months was documented in 30.2% and 6.3% of patients, respectively (p = 0.003). There was a significant difference between groups in %IOP reduction after 12 months. Greater reduction was observed in Preserflo group, MD = - 8.41 CI95 [- 15.88; - 0.95], p = 0.028, (- 33.49% ± 21.59 vs - 25.07% ± 14.15 in iStent group). Both procedures effectively reduced IOP and postoperative use of antiglaucoma medications in glaucoma patients.

Comparing the safety and efficacy of Preserflo Microshunt implantation and trabeculectomy for glaucoma: A systematic review and meta-analysis

To compare the safety and efficacy of the Preserflo Microshunt with trabeculectomy in the treatment of patients with glaucoma. A systematic review and meta-analysis was conducted. The primary outcome measures recorded as a measure of efficacy of the interventions were intra-ocular pressure (IOP) at final follow-up and IOP reduction (IOPR). Secondary outcomes recorded to measure efficacy were reduction in the number of glaucoma medications and reinterventions. To assess safety profile, the proportions of patients with post-operative complications were recorded. Seven articles were included in this study. A total of 1353 eyes were included in this review (Preserflo: 812, trabeculectomy: 541). Post-operative IOP (mean difference [MD] = 0.78 [0.66, 0.90], p < 0.001) results are significantly lower for trabeculectomy than Preserflo. The IOPR (MD = -1.20 [-2.30, -0.09], p = 0.034) results significantly favour trabeculectomy over Preserflo Microshunt. The reduction in topical glaucoma medications (MD = -0.32 [-0.58, -0.07], p = 0.014) is significantly higher for trabeculectomy. There is no statistically significant difference in levels of hypotony (risk ratio [RR] = -0.05 [-0.47, 0.37], p = 0.806), choroidal effusion/detachment (RR = -0.12 [-0.42, 0.19], p = 0.444), hyphaema (RR = 0.20 [-0.11, 0.51], p = 0.216) and flat anterior chamber (RR = 0.49 [-1.02, 0.03], p = 0.066). There are significantly more bleb-related complications in the trabeculectomy groups than Preserflo groups (RR = -0.63 [-1.01, -0.24], p = 0.001). There were statistically more reinterventions required in the trabeculectomy groups than Preserflo groups (RR = -0.48 [-0.65, -0.30], p < 0.001). Compared to trabeculectomy, the Preserflo Microshunt is not as effective in lowering intra-ocular pressure, has a similar safety profile and has a lower reintervention rate. Further research is required given the lack of randomised controlled trials within this study and resulting low strength of evidence.

Intraoperative primary partial occlusion of the PreserFlo MicroShunt to prevent initial postoperative hypotony

PURPOSE

The aim of the underlying study was to present a new surgical method in PreserFlo MicroShunt surgery for glaucoma. A removable polyamide suture was placed into the lumen of the MicroShunt during implantation to prevent early postoperative hypotony.

METHODS

Thirty-one patients undergoing stand-alone glaucoma surgery with implantation of a PreserFlo MicroShunt and an intraluminal occlusion were retrospectively reviewed and compared to a control group without occlusion. Inclusion criteria were diagnosis of primary open-angle glaucoma or secondary open-angle glaucoma due to pseudoexfoliation or pigment dispersion. Patients with a history of filtrating glaucoma surgery were excluded.

RESULTS

IOP decreased from 26.9 ± 6.6 to 18.0 ± 9.5 mmHg at the first postoperative day after PreserFlo MicroShunt implantation. Postoperative removal of the occluding suture resulted in a mean IOP reduction in 11.1 ± 7.6 mmHg. Mean visual acuity was 0.43 ± 0.24 logMAR during the first postoperative examination. The interval with the occluding intraluminal suture in place varied from days to 2-3 weeks. Patients were followed up to 1 year.

CONCLUSION

Implantation of a PreserFlo MicroShunt combined with an intraluminal suture prevented postoperative hypotony in all patients. Mean postoperative pressure was reduced despite the occluding suture in place.

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.

The PreserFlo MicroShunt in the Context of Minimally Invasive Glaucoma Surgery: A Narrative Review

Recently, the quest for novel glaucoma surgical techniques and devices has been underway. Trabeculectomy remains the gold standard, but it requires the implantation of glaucoma drainage devices and frequent follow-ups, and it also carries a high risk of serious complications. The need for less invasive and safer procedures has led to the development of minimally invasive glaucoma surgery (MIGS), particularly for patients with mild-to-moderate disease. Among them, minimally invasive bleb surgery seems to be effective in classical glaucoma surgery, while maintaining MIGS benefits. The relatively new PreserFlo® MicroShunt (Santen, Osaka, Japan) is registered in Europe. It was released in 2019 for the treatment of patients with early-to-advanced open-angle glaucoma, where intraocular pressure (IOP) remains uncontrolled while on maximum tolerated medication and/or where glaucoma progression warrants surgery. This review focuses on the place of the PreserFlo MicroShunt, characterized by ab externo implantation, among MIGS procedures, discussing its advantages and disadvantages. The mechanisms of action, technical aspects, efficacy, and safety issues are summarized. The surgical technique, its efficacy, and safety profile are described, and directions for future studies are indicated. The PreserFlo MicroShunt ensures a high safety profile, minimal anatomical disruption, meaningful IOP-lowering effect, and ease of use for patients and physicians.

Comparative Cost-effectiveness of Trabeculectomy versus MicroShunt in the US Medicare System

PURPOSE

To assess the societal cost-utility of the MicroShunt compared with trabeculectomy for the surgical management of glaucoma in the US Medicare system.

DESIGN

Cost-utility analysis using efficacy and safety results of a randomized controlled trial and other pivotal clinical trials.

PARTICIPANTS

Markov model cohort of patients with open-angle glaucoma.

METHODS

Open-angle glaucoma treatment costs and effects were analyzed with a deterministic model over a 1-year horizon using TreeAge software. Health states included the Hodapp-Parrish-Anderson glaucoma stages (mild, moderate, advanced, blind) and death. Both treatment arms received additional ocular hypotensive agents to control intraocular pressure (IOP). Treatment effect was measured as mean number of ocular hypotensive medications and reduction in IOP, which had a direct impact on transition probabilities between health states. Analyses of scenarios were performed with longer time horizons. One-way sensitivity and probabilistic sensitivity analyses were conducted to assess the impact of alternative model inputs. Both treatment arms were subject to reported complication rates, which were factored in the model.

MAIN OUTCOME MEASURES

Incremental cost per quality-adjusted life-year (QALY) gained.

RESULTS

At 1 year, the MicroShunt had an expected cost of US dollars (USD) 6318 compared with USD 4260 for trabeculectomy. MicroShunt patients gained 0.85 QALYs compared with 0.86 QALYs for trabeculectomy, resulting in a dominated incremental cost-utility ratio of USD 187 680. Dominance is a health economic term used to describe a treatment option that is both more costly and less effective than the alternative. The MicroShunt remained dominant in 1-way sensitivity analyses using best-case input parameters (including a device fee of USD 0). At a willingness-to-pay threshold of USD 50 000, the likelihood of the MicroShunt being cost-effective was 6.4%. Dominance continued in longer time horizons, up to 20 years.

CONCLUSIONS

Trabeculectomy appears to be a dominant treatment strategy over the MicroShunt in the surgical management of glaucoma. More independent, long-term studies are required for the MicroShunt and other subconjunctival microstent devices to evaluate their use in clinical practice.

PreserFlo™ MicroShunt Versus Trabeculectomy in Patients With Moderate to Advanced Open-Angle Glaucoma: 12-Month Follow-Up of a Single-Center Prospective Study

Purpose: The study compares the efficacy and safety of PreserFlo™ MicroShunt (Santen, Osaka, Japan) and trabeculectomy in eyes with moderate to advanced open-angle glaucoma.

Methods: In this prospective study, 300 patients (300 eyes) with moderate to advanced open-angle glaucoma were treated with either PreserFlo MicroShunt or trabeculectomy. The implantation of the PreserFlo MicroShunt was performed in 150 eyes (group A) and trabeculectomy was performed in 150 eyes (group B). The efficacy was evaluated by estimating the absolute and qualified success rates using the Kaplan-Meier survival analysis. 

Results: During the 12-month follow-up period, 81.33% of eyes in group A and 94% in group B reduced intraocular pressure (IOP) >20% without glaucoma eye drops. The average IOP 12 months after surgery was 12.89±3.4 mmHg in group A and 11.39±4.5 mmHg in group B, which was significantly lower than the baseline intraocular pressure (group A: 23.47±8.36 mmHg, p=0.00053; group B: 22.03±5.2 mmHg, p= 0.0006). The number of topical medications administered 12 months after ocular surgery was 0.4±0.8 in group A and 0 in group B, compared to 2.5±1.2 in group A and 2.7±0.9 in group B at baseline (group A: p= 0.00091; group B: p= 0.00072). Ten eyes (6.67%) in group A and four eyes (2.67%) in group B were referred for bleb revision due to bleb fibrosis and consequent acute postoperative rise in IOP. Four eyes of group A and two eyes of group B were treated with transscleral cyclophotocoagulation. Five eyes in group B received re-trabeculectomy because of dysfunction of the primary bleb.

Conclusion: PreserFlo MicroShunt reduced the number of antiglaucoma agents compared to baseline, but was inferior to trabeculectomy at reducing IOP after 12 months. Additionally, trabeculectomy produced better absolute success rates after 12 months than PreserFlo MicroShunt in the treatment of moderate to advanced open-angle glaucoma.

Evaluation of a Novel Αb Εxterno MicroShunt for the Treatment of Glaucoma

The surgical management of glaucoma has been revolutionized by the introduction of minimally invasive glaucoma surgery (MIGS). The various MIGS options aim to meaningfully lower intraocular pressure with a better safety profile than traditional glaucoma surgery. The key clinical attributes and the emerging potential of an ab externo MicroShunt (PreserFlo™) are reviewed in the context of published evidence and clinical experience. This novel MicroShunt consists of an 8.5-mm-long tube that is implanted in the eye via an ab externo approach enabling aqueous humor drainage into the sub-Tenon’s space through the formation of a bleb, similar in appearance to that created by trabeculectomy. The efficacy and safety of this procedure, the concomitant use of antimetabolites, the impact of tube positioning, and its future value in clinical practice are critically reviewed. Recent evidence has demonstrated the MicroShunt to be less effective than traditional filtration surgery, but with a significant improvement in safety. Cumulative data suggest that the new implant provides tangible clinical benefits to selected patients with glaucoma in need of further intraocular pressure (IOP) lowering. Future research should delineate the precise role of this and other MIGS options in the rapidly evolving glaucoma treatment algorithm.

Microinvasive glaucoma surgery: a review and classification of implant-dependent procedures and techniques

The aim of this article is to discuss how physiology and anatomical background affect the effectiveness of implant‐dependent microinvasive glaucoma surgery (MIGS). First, we provide a micro view of aqueous outflow and tissue behaviour. Second, we review studies exploring the mechanisms of the pressure‐lowering effect of MIGS, as well as tissue behaviour during aqueous flow and tissue motion. We also describe and classify microinvasive surgical procedures and the most important types of implants, as well as their mechanisms of action, implantation techniques and efficacy. Further, we summarize the indications and surgical results presented in recent studies, providing an evidence‐based update on novel and emerging MIGS techniques for the treatment of open‐angle glaucoma. These data can help surgeons to personalize the management of glaucoma and to choose the best MIGS option for individual glaucoma patients.

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.

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.

PreserFlo™ microshunt combined with phacoemulsification versus preserflo™ MicroShunt as a standalone procedure in patients with medically resistant open-angle glaucoma

Purpose:

To compare the efficacy and safety of PreserFlo™ MicroShunt (Santen, Osaka, Japan) combined with phacoemulsification to PreserFlo™ MicroShunt as a standalone procedure in eyes with moderate to advanced open-angle glaucoma.

Methods:

In an observatory, prospective, clinical study, 30 patients (30 eyes) with moderate to advanced angle glaucoma were allocated to either PreserFlo™ MicroShunt combined with phacoemulsification (15 eyes; Group A) or PreserFlo™ MicroShunt as a standalone procedure (15 eyes; Group B). The follow-up time of the study was 12 months.

Results:

Average intraocular pressure (IOP) at 12 months was 11.62 ± 1.6 mmHg in Group A and 13.8 ± 3.6 mmHg in Group B, which was significantly lower than baseline IOP (Group A: 23.47 ± 8.99 mmHg, P < 0.001; Group B: 23.4 ± 8.68 mmHg, P < 0.001). The absolute reduction of IOP within the 12 postoperative months was not significantly different between the two groups (P = 0.056). The number of the topical medications that were administered 12 months after ocular surgery was 0 in Group A and 0.6 ± 0.8 in Group B, compared to 3.13 ± 1.02 in Group A (P < 0.001) and 2.4 ± 1.45 in Group B (P = 0.004) at baseline. Phacoemulsification combined with PreserFlo™ MicroShunt significantly reduced the number of antiglaucoma agents after 12 months compared to the standalone procedure (P = 0.026). One eye in Group A was referred for bleb revision due to bleb fibrosis and a consequent acute postoperative rise in IOP. One eye in Group A required transscleral cyclophotocoagulation with MicroPulse^® laser. One bleb revision was also necessary in Group B at the 4^th postoperative week. Endothelial cell density did not significantly change over 12 months in either group (Group A: baseline, 2017.3 ± 346.8 cells/mm^[2]; 12 months, 1968.5 ± 385.6 cells/mm^[2]; P = 0.38; Group B: baseline, 2134.1 ± 382.6 cells/mm^[2]; 12 months, 2094.4 ± 373.3 cells/mm^[2], P = 0.42). The PreserFlo™ MicroShunt combined with phacoemulsification produced higher absolute success rates after 12 months in patients with moderate to advanced open-angle glaucoma than the PreserFlo™ MicroShunt as standalone procedure (Group A: 80% and Group B: 60%, P = 0.022).

Conclusions:

In eyes with moderate to advanced open-angle glaucoma, PreserFlo™ MicroShunt with or without phacoemulsification is effective in reducing IOP and the number of the antiglaucoma agents with a very small incidence of complications and subsequent glaucoma surgeries. However, adding phacoemulsification to PreserFlo™ MicroShunt successfully reduces IOP without the need for ongoing topical medications as are needed after the standalone procedure.

The use of polyisobutylene-based polymers in ophthalmology

A novel polyolefin called poly(styrene-block-isobutylene-block-styrene) (“SIBS”) originated from Joseph P. Kennedy's laboratory at the University of Akron (Akron, Ohio, United States) and was developed as a biomaterial for long-term implant applications by the author. SIBS has no cleavable groups on its backbone or sidechains, is comprised predominantly of alternating secondary and quaternary carbons on its backbone, which prevents embrittlement and cracking under flexion, and undergoes multiple purification steps which renders it extremely biocompatible and well-suited for long-term applications in the eye. This article explores two ophthalmic devices; 1) the PRESERFLO® MicroShunt (Santen Pharmaceutical Co. Ltd., Osaka, Japan) made from SIBS that lowers intraocular pressure to thwart progression of vision loss from glaucoma, and 2) a novel intraocular lens (IOL) made from crosslinked polyisobutylene, which is under-development by Xi'an Eyedeal Medical Technology Co., Ltd. (Xi'an, China) that does not glisten nor cloud over time, as do most conventional IOLs.

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A novel class of ultra-biostable polyisobutylene-based biomaterials for long-term implant applications.

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A novel class of polyisobutylene-based biomaterials that is not bioactive and elicits minimal foreign body reaction.

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A device called the PRESERFLO® MicroShunt to treat glaucoma made from poly(styrene-block-isobutylene-block-styrene) (SIBS).

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A novel crosslinked polyisobutylene material for intraocular lens applications that eliminates glistenings and halos.

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.

Parylene-C Microbore Tubing: A Simpler Shunt for Reducing Intraocular Pressure

OBJECTIVE

Current minimally-invasive glaucoma surgery (MIGS) devices promise to control elevated levels of intraocular pressure (IOP) while avoiding many of the downsides of traditional glaucoma surgery. However, there remains room for improvement in performance metrics, including drainage efficacy, device longevity, and time to implant, as outlined by benchmarks set forth by the Audacious Goals Initiative. We introduce a better shunt, which achieves similar or improved pre-clinical safety and efficacy outcomes to commercial MIGS devices, while reducing surgical profile and implantation time.

METHODS

We developed a parylene-based microbore glaucoma drainage device capable of modulating IOP via a minimally-invasive implantation procedure. We surgically implanted microbore tubing in five healthy New Zealand White rabbits and measured IOP levels biweekly using handheld applanation tonometry to assess device efficacy in lowering and maintaining IOP. After 6 weeks, the rabbits were euthanized and eyes were enucleated to evaluate inflammatory and histologic response to a foreign-body implant.

RESULTS

This device is the only one that fulfills the 10-minute benchmark for implantation time compared to other commercial MIGS devices. In 4 of 5 animals implanted, post-op IOP in the experimental eye dropped by an average of 16.17%. Histopathologic evaluation revealed localized evidence of minor inflammatory reaction and tissue irritation, as well as minimal fibrosis along the tube-tissue interface.

CONCLUSION AND SIGNIFICANCE

Based on these findings, this device stands as a promising platform to lowering IOP, particularly in patients with mild to moderate glaucoma requiring no need for cataract intervention, without eliciting a severe biological response.

Minimally Invasive Glaucoma Surgery: A Critical Appraisal of the Literature

Micro- or minimally invasive glaucoma surgeries (MIGS) have been the latest addition to the glaucoma surgical treatment paradigm. This term refers not to a single surgery, but rather to a group of distinct procedures and devices that aim to decrease intraocular pressure. Broadly, MIGS can be categorized into surgeries that increase the trabecular outflow [Trabectome, iStent (first and second generations), Hydrus microstent, Kahook Dual Blade and gonioscopy-assisted transluminal trabeculotomy], surgeries that increase suprachoroidal outflow (Cypass microstent and iStent Supra), and conjunctival bleb-forming procedures (Xen gel stent and InnFocus microshunt). Compared to traditional glaucoma surgeries, such as trabeculectomy and glaucoma drainage device implantation (Ahmed, Baerveldt, and Molteno valves), MIGS are touted to have less severe complications and shorter surgical time. MIGS represent an evolving field, and the efficacy and complications of each procedure should be considered independently, giving more importance to high-quality and longer-term studies.

Ab-Externo MicroShunt versus Trabeculectomy in Primary Open-Angle Glaucoma: One-Year Results from a 2-Year Randomized, Multicenter Study

PURPOSE

To compare the effectiveness and safety of the MicroShunt versus trabeculectomy in patients with primary open-angle glaucoma (POAG).

DESIGN

One-year results from a 2-year, prospective, randomized, multicenter, noninferiority study (NCT01881425) conducted in the United States and Europe.

PARTICIPANTS

Eligible patients were aged 40-85 years with intraocular pressure (IOP) ≥15 and ≤40 mmHg and mild-to-severe POAG inadequately controlled on maximum tolerated medical therapy.

METHODS

Patients were randomized 3:1 to undergo stand-alone MicroShunt implantation or trabeculectomy, both performed with adjunctive mitomycin C (0.2 mg/ml for 2 minutes).

MAIN OUTCOME MEASURES

The primary effectiveness end point was surgical success, defined as ≥20% reduction in mean diurnal IOP from baseline (no medication washout) at year 1 without increasing the number of glaucoma medications. Secondary effectiveness end points at year 1 were the mean IOP change from baseline and requirement for postoperative intervention. Additional end points included glaucoma medication use and adverse events.

RESULTS

Overall, 395 (MicroShunt) and 132 (trabeculectomy) patients were randomized (mean Humphrey visual field mean deviation, -12.34 decibels [dB]). At year 1, probability of success was lower in the MicroShunt group compared with the trabeculectomy group (53.9% vs. 72.7%, respectively; P < 0.01). In the MicroShunt group, mean IOP ± standard deviation decreased from 21.1 ± 4.9 mmHg at baseline to 14.3 ± 4.3 mmHg (-29.1%; P < 0.01) at year 1, with a mean of 0.6 ± 1.1 glaucoma medications (baseline 3.1 ± 1.0; P < 0.01). In the trabeculectomy group, mean IOP decreased from 21.1 ± 5.0 mmHg to 11.1 ± 4.3 mmHg (-45.4%; P < 0.01), with a mean of 0.3 ± 0.9 glaucoma medications (baseline 3.0 ± 0.9; P < 0.01). Postoperative interventions, including laser suture lysis, were reported in 40.8% (MicroShunt) versus 67.4% (trabeculectomy) of patients (P < 0.01). Reported incidence of transient hypotony was higher in the trabeculectomy group versus the MicroShunt group (49.6% vs. 28.9%; P < 0.01). Vision-threatening complications were uncommon and reported in 1.0% of MicroShunt versus 0.8% of trabeculectomy patients.

CONCLUSIONS

Probability of success was lower with MicroShunt compared with trabeculectomy. Although reductions in IOP and glaucoma medications over 1 year were observed in both groups, the trabeculectomy group had a lower mean IOP on fewer medications.

Effectiveness and limitations of minimally invasive glaucoma surgery targeting Schlemm's canal

Glaucoma surgery is performed to lower intraocular pressure (IOP); ideally, the IOP reduction is safely maintained for an extended period of time. Although trabeculectomy was considered the gold standard for glaucoma surgery for many years because of its effective IOP reduction, yet now it is considered unsafe because of serious complications. In recent years, minimally invasive glaucoma surgery (MIGS), which emphasizes safety and can be performed rapidly, has become widespread. Because MIGS does not involve conjunctival incisions, patients can undergo future trabeculectomy. If IOP reduction can be maintained safely, the number of anti-glaucoma drops can be reduced and visual function maintained, good outcomes for patients with glaucoma. Currently, many types of MIGS approved in Japan are reported to yield relatively good results, with targets of approximately 15-19 mmHg. However, the IOP-lowering effects of MIGS are limited. In procedures targeting Schlemm's canal, it is difficult to lower IOP beyond episcleral venous pressure. In some instances, a beneficial effect cannot be achieved if function is reduced beyond the collector channel. There are many unclear aspects regarding long-term outcomes following MIGS. Notably, investigation is ongoing to determine which patients are likely to benefit most from surgery. Based on previous reports, this review describes the characteristics and results of MIGS, approved in Japan, as well as underlying factors that affect the preoperative predictions and outcomes of the surgical procedure.

Ab externo implantation of the MicroShunt, a poly (styrene-block-isobutylene-block-styrene) surgical device for the treatment of primary open-angle glaucoma: a review

Trabeculectomy remains the ‘gold standard’ intraocular pressure (IOP)-lowering procedure for moderate-to-severe glaucoma; however, this approach is associated with the need for substantial post-operative management. Micro-invasive glaucoma surgery (MIGS) procedures aim to reduce the need for intra- and post-operative management and provide a less invasive means of lowering IOP. Generally, MIGS procedures are associated with only modest reductions in IOP and are targeted at patients with mild-to-moderate glaucoma, highlighting an unmet need for a less invasive treatment of advanced and refractory glaucoma. The PRESERFLO® MicroShunt (formerly known as InnFocus MicroShunt) is an 8.5 mm-long (outer diameter 350 μm; internal lumen diameter 70 μm) glaucoma drainage device made from a highly biocompatible, bioinert material called poly (styrene-block-isobutylene-block-styrene), or SIBS. The lumen size is sufficiently small that at normal aqueous flow hypotony is avoided, but large enough to avoid being blocked by sloughed cells or pigment. The MicroShunt achieves the desired pressure range in the eye by draining aqueous humor from the anterior chamber to a bleb formed under the conjunctiva and Tenon’s capsule. The device is implanted ab externo with intraoperative Mitomycin C via a minimally invasive (relative to incisional surgery) surgical procedure, enabling precise control of placement without the need for gonioscopy, suture tension control, or suture lysis. The implantation procedure can be performed in combination with cataract surgery or as a standalone procedure. The MicroShunt received Conformité Européenne (CE) marking in 2012 and is intended for the reduction of IOP in eyes of patients with primary open-angle glaucoma in which IOP remains uncontrolled while on maximum tolerated medical therapy and/or in which glaucoma progression warrants surgery. Three clinical studies assessing the long-term safety and efficacy of the MicroShunt have been completed; a Phase 3 multicenter, randomized clinical study comparing the MicroShunt to primary trabeculectomy is underway. In preliminary studies, the MicroShunt effectively reduced IOP and use of glaucoma medications up to 3 years after implantation, with an acceptable safety profile. This article summarizes current literature on the unique properties of the MicroShunt, the preliminary efficacy and safety findings, and discusses its potential use as an alternative to trabeculectomy for glaucoma surgery.

Minimally Invasive Glaucoma Surgery with a New Ab-externo Subconjunctival Bypass – Current Status and Review of Literature

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iDrugs and iDevices Discovery Research: Preclinical Assays, Techniques, and Animal Model Studies for Ocular Hypotensives and Neuroprotectants

Discovery ophthalmic research is centered around delineating the molecular and cellular basis of ocular diseases and finding and exploiting molecular and genetic pathways associated with them. From such studies it is possible to determine suitable intervention points to address the disease process and hopefully to discover therapeutics to treat them. An investigational new drug (IND) filing for a new small-molecule drug, peptide, antibody, genetic treatment, or a device with global health authorities requires a number of preclinical studies to provide necessary safety and efficacy data. Specific regulatory elements needed for such IND-enabling studies are beyond the scope of this article. However, to enhance the overall data packages for such entities and permit high-quality foundation-building publications for medical affairs, additional research and development studies are always desirable. This review aims to provide examples of some target localization/verification, ocular drug discovery processes, and mechanistic and portfolio-enhancing exploratory investigations for candidate drugs and devices for the treatment of ocular hypertension and glaucomatous optic neuropathy (neurodegeneration of retinal ganglion cells and their axons). Examples of compound screening assays, use of various technologies and techniques, deployment of animal models, and data obtained from such studies are also presented.

Three-Year Follow-up of a Novel Aqueous Humor MicroShunt

AIMS

An observational study to determine the safety and efficacy of filtering surgery employing a microlumen aqueous drainage device (InnFocus MicroShunt), used intraoperatively with Mitomycin C, implanted alone or in combination with phacoemulsification.

MATERIALS AND METHODS

Single-site, prospective, nonrandomized study of 23 eyes that had failed maximum tolerated glaucoma medication, followed for 3 years. A MicroShunt was implanted ab externo through a needle tract under the limbus, draining aqueous from the anterior chamber to the scleral surface. Prespecified outcome measures include: intraocular pressure (IOP) control, with and without supplemental medication, success rate, medication use, and adverse events.

RESULTS

Fourteen patients received the MicroShunt alone and 9 with cataract surgery. At 1 (n=23), 2 (n=22), and 3 (n=22) years of follow-up; the qualified success rate (IOP ≤ 14 mm Hg and IOP reduction ≥ 20%) was 100%, 91%, and 95%; mean medicated IOP was reduced from 23.8 ± 5.3 to 10.7 ± 2.8, 11.9 ± 3.7, and 10.7 ± 3.5 mm Hg, and the mean number of glaucoma medications/patient was reduced from 2.4 ± 0.9 to 0.3 ± 0.8, 0.4 ± 1.0, and 0.7 ± 1.1, respectively. The most common complications were transient hypotony (13%, 3/23) and transient choroidal effusion (8.7%, 2/23), all resolved spontaneously. There were no leaks, infections, migrations, erosions, persistent corneal edema, or serious long-term adverse events.

CONCLUSION

Surgery with the InnFocus MicroShunt transscleral aqueous drainage tube with Mitomycin C achieved IOP control in the low teens in most subjects up to 3 years of follow-up with only transient adverse events occurring within the first 3 months after surgery.

The use of poly(styrene-block-isobutylene-block-styrene) as a microshunt to treat glaucoma

The InnFocus MicroShunt® is a minimally invasive glaucoma drainage microtube used to shunt aqueous humor from the anterior chamber of the eye to a flap formed under the conjunctiva and Tenon’s capsule. The safety and clinical performance of this device approaches that of trabeculectomy with mitomycin C, the current ‘gold standard’ treatment for advanced glaucoma. The invention of a new biomaterial called poly(styrene-block-isobutylene-block-styrene) or ‘SIBS’ is the enabling factor which led to the success of this product. SIBS is ultrastable with virtually no foreign body reaction in the body, which manifests as clinically insignificant inflammation and capsule formation in the eye. The lack of capsule formation enables unobstructed flow through the 70 µm lumen tube and the achievement of controlled low intraocular pressure, which is important for the management of glaucoma. This article summarizes the integration of SIBS into a glaucoma drainage device and confirms its functionality with clinical success over a 2-year period.

The development of a micro-shunt made from poly(styrene-block-isobutylene-block-styrene) to treat glaucoma

Glaucoma is the second leading cause of blindness with ∼70 million people worldwide who are blind from this disease. The currently practiced trabeculectomy surgery, the gold standard treatment used to stop the progression of vision loss, is rather draconian, traumatic to the patient and requires much surgical skill to perform. This article summarizes the more than 10‐year development path of a novel device called the InnFocus MicroShunt®, which is a minimally invasive glaucoma drainage micro‐tube used to shunt aqueous humor from the anterior chamber of the eye to a flap formed under the conjunctiva and Tenon's Capsule. The safety and clinical performance of this device approaches that of trabeculectomy. The impetus to develop this device stemmed from the invention of a new biomaterial called poly(styrene‐block‐isobutylene‐block‐styrene), or “SIBS.” SIBS is ultra‐stable with virtually no foreign body reaction in the body, which manifests in the eye as clinically insignificant inflammation and capsule formation. The quest for an easier, safer, and more effective method of treating glaucoma led to the marriage of SIBS with this glaucoma drainage micro‐tube. This article summarizes the development of SIBS and the subsequent three iterations of design and four clinical trials that drove the one‐year qualified success rate of the device from 43% to 100%. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 211–221, 2017.

Glaucoma surgery: taking the sub-conjunctival route

We are currently in the midst of a surge in interest in glaucoma surgery. Novel pathways for reducing intraocular pressure (IOP) have been tried with various levels of success over the last few years. While the trabecular bypass and suprachoroidal approaches have captured much of the attention, filtering aqueous into the sub-conjunctival space remains the gold standard for lowering IOP. This review attempts to focus on current research in surgical methods to enhance filtration by potentially improving on tried and tested methods like the trabeculectomy, deep sclerectomy, and tube surgeries.

Polymeric trileaflet prosthetic heart valves: evolution and path to clinical reality

Present prosthetic heart valves, while hemodynamically effective, remain limited by progressive structural deterioration of tissue valves or the burden of chronic anticoagulation for mechanical valves. An idealized valve prosthesis would eliminate these limitations. Polymeric heart valves (PHVs), fabricated from advanced polymeric materials, offer the potential of durability and hemocompatibility. Unfortunately, the clinical realization of PHVs to date has been hampered by findings of in vivo calcification, degradation and thrombosis. Here, the authors review the evolution of PHVs, evaluate the state of the art of this technology and propose a pathway towards clinical reality. In particular, the authors discuss the development of a novel aortic PHV that may be deployed via transcatheter implantation, as well as its optimization via device thrombogenicity emulation.