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

Electrochemically-driven actuators: from materials to mechanisms and from performance to applications

Soft actuators, pivotal for converting external energy into mechanical motion, have become increasingly vital in a wide range of applications, from the subtle engineering of soft robotics to the demanding environments of aerospace exploration. Among these, electrochemically-driven actuators (EC actuators), are particularly distinguished by their operation through ion diffusion or intercalation-induced volume changes. These actuators feature notable advantages, including precise deformation control under electrical stimuli, freedom from Carnot efficiency limitations, and the ability to maintain their actuated state with minimal energy use, akin to the latching state in skeletal muscles. This review extensively examines EC actuators, emphasizing their classification based on diverse material types, driving mechanisms, actuator configurations, and potential applications. It aims to illuminate the complicated driving mechanisms of different categories, uncover their underlying connections, and reveal the interdependencies among materials, mechanisms, and performances. We conduct an in-depth analysis of both conventional and emerging EC actuator materials, casting a forward-looking lens on their trajectories and pinpointing areas ready for innovation and performance enhancement strategies. We also navigate through the challenges and opportunities within the field, including optimizing current materials, exploring new materials, and scaling up production processes. Overall, this review aims to provide a scientifically robust narrative that captures the current state of EC actuators and sets a trajectory for future innovation in this rapidly advancing field.

Additional Guidance on the Use of the PRESERFLO™ MicroShunt in the Treatment of Glaucoma: Insights from a Second Delphi Consensus Panel

INTRODUCTION

The PRESERFLO™ MicroShunt (PMS) has been proven to significantly lower intraocular pressure (IOP) in patients with glaucoma and has been available for use since 2019. With increasing published evidence and growing experience of glaucoma surgeons, the aim of this modified Delphi panel was to build on the findings of a previous Delphi panel conducted in 2021 and provide further guidance on the role of the PMS to treat patients with glaucoma in Europe.

METHODS

Thirteen European glaucoma surgeons experienced in the PMS procedure participated in a 3-round modified Delphi panel. A targeted literature review and expert steering committee guided Round 1 questionnaire development. Consensus was pre-defined at a threshold of ≥ 70% of panellists selecting 'strongly agree'/'agree' or 'strongly disagree'/'disagree' for 6-point Likert scale questions or ≥ 70% selecting the same option for multiple or single-choice questions. Questions not reaching consensus were restated/revised for the next round, following guidance from free-text responses/scoping questions.

RESULTS

In total, 28% (n = 9/32), 52% (n = 16/31) and 91% (n = 10/11) of statements reached consensus in Rounds 1, 2 and 3, respectively. There was agreement that the PMS may be used in patients with pigmentary, post-trauma or post-vitrectomy glaucoma and for patients with uveitic glaucoma without active inflammation. The PMS may be more suitable for patients with contact lenses than other subconjunctival filtering surgeries, without eliminating bleb-associated risks. Consensus was reached that combining PMS implantation and phacoemulsification may be as safe as standalone PMS surgery, but further efficacy data are required. Following a late rise in IOP ≥ 4 months post-surgery, topical aqueous suppressant drops or bleb revision may be suitable management options.

CONCLUSIONS

This Delphi panel builds on the considerations explored in the 2021 Delphi panel and provides further detailed guidance for glaucoma surgeons on the use of the PMS, reflecting the availability of novel evidence and surgical experience. Videos are available for this article.

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.

Bleb vessel density as a predictive factor for surgical revisions after Preserflo Microshunt implantation

PURPOSE

Bleb failure is a common complication after glaucoma filtration surgery. Different bleb classification schemes incorporating filtration bleb vascularization have been proposed, but the reported correlation with intraocular pressure (IOP) has been variable, possibly because of subjective vascularization grading. The purpose of the present study was to evaluate bleb vascularization after Preserflo Microshunt (PM) implantation using anterior segment OCT-angiography (AS-OCTA) as a biomarker for bleb failure.

METHODS

Twenty-three eyes of twenty-three patients underwent PM implantation. Up to 12 months after surgery PM scleral passage-centred AS-OCTA measurements (PLEX Elite 9000) for bleb-vessel density (BVD) determination were performed and IOP as well as necessity for surgical revisions (needling and open revision) were documented. After multi-step image analysis (region of interest definition, artefact removal, binarization, BVD calculation), the predictive value of early postoperative BVD for surgical revisions was assessed using logistic regression modelling.

RESULTS

Baseline IOP (23.57 ± 7.75 mmHg) decreased significantly to 8.30 ± 2.12, 9.17 ± 2.33 and 11.70 ± 4.40 mmHg after 1, 2 and 4 week(s), and 13.48 ± 5.83, 11.87 ± 4.49, 12.30 ± 6.65, 11.87 ± 3.11 and 13.05 ± 4.12 mmHg after 2, 3, 6, 9 and 12 month(s), respectively (p < 0.001). Nine patients (39%) needed surgical revisions after a median time of 2 months. Bleb vessel densities at 2 and 4 weeks were significantly associated with future surgical revisions upon logistic regression analysis (2 W/4 W likelihood-ratio test p-value: 0.0244/0.0098; 2 W/4 W area under the receiver operating characteristics curve: 0.796/0.909).

CONCLUSION

Filtration bleb vessel density can be determined using AS-OCTA in the early postoperative period and is predictive for bleb failure after PM implantation.

Standard anterior peritomy versus a small posterior incision for the implantation of the PRESERFLO microshunt

PURPOSE

To compare two approaches for the implantation of the PRESERFLO microshunt: an anterior approach (A) with a 6-8-mm peritomy and a posterior approach (P) with a 3-mm incision.

METHODS

We retrospectively analyzed 126 patients who received a PRESERFLO microshunt. We compared intraocular pressure (IOP), surgical time, medication count, and postoperative complications over nine months.

RESULTS

The baseline IOP was similar in A (21.8 ± 8.5 mm Hg) and P (23.9 ± 8.1 mm Hg) (p = 0.08). Surgical duration was significantly shorter in P (10 ± 0.4 min) than in A (26 ± 0.8 min) (p < 0.001). Postoperative IOP levels were comparable in A (10.8 ± 5.9 mm Hg) and P (10.6 ± 4.5 mm Hg) at 30 days (p = 0.62) and throughout the study (all intra-group p-values > 0.08). The preoperative medication count was 3.2 ± 1.3 drops in A and 3.3 ± 1.0 drops in P (p = 0.4). Postoperative values were 0.2 ± 0.6 in A and 0.3 ± 0.7 in P at nine months. There were no significant differences in complications and surgical revisions between groups (p-values > 0.05).

CONCLUSION

Both techniques achieved satisfactory IOP and medication count reductions and had similar safety profiles, but the posterior incision technique was 2.6 times faster than the anterior incision technique.

Microfluidics in the eye: a review of glaucoma implants from an engineering perspective

Glaucoma is a progressive optic neuropathy in the eye, which is a leading cause of irreversible blindness worldwide and currently affects over 70 million individuals. Clinically, intraocular pressure (IOP) reduction is the only proven treatment to halt the progression of glaucoma. Microfluidic devices such as glaucoma drainage devices (GDDs) and minimally invasive glaucoma surgery (MIGS) devices are routinely used by ophthalmologists to manage elevated IOP, by creating an artificial pathway for the over-accumulated aqueous humor (AH) in a glaucomatous eye, when the natural pathways are severely blocked. Herein, a detailed modelling and analysis of both the natural microfluidic pathways of the AH in the eye and artificial microfluidic pathways formed additionally by the various glaucoma implants are conducted to provide an insight into the causes of the IOP abnormality and the improvement schemes of current implant designs. The mechanisms of representative glaucoma implants have been critically reviewed from the perspective of microfluidics, and we have categorized the current implants into four groups according to the targeted drainage sites of the AH, namely Schlemm's canal, suprachoroidal space, subconjunctival space, and ocular surface. In addition, we propose to divide the development and evolution of glaucoma implant designs into three technological waves, which include microtube (1st), microvalve (2nd) and microsystem (3rd). With the emerging trends of minimal invasiveness and artificial intelligence in the development of medical implants, we envision that a comprehensive glaucoma treatment microsystem is on the horizon, which is featured with active and wireless control of IOP, real-time continuous monitoring of IOP and aqueous rate, etc. The current review could potentially cast light on the unmatched needs, challenges, and future directions of the microfluidic structural and functional designs of glaucoma implants, which would enable an enhanced safety profile, reduced complications, increased efficacy of lowering IOP and reduced IOP fluctuations, closed-loop and on-demand control of IOP, etc.

Dislocation of the PreserFlo MicroShunt During a Postsurgical Needling Procedure

We report a case of PreserFlo MicroShunt (PFM) dislocation following a postsurgical needling procedure. A 58-year-old woman underwent PFM implantation for exfoliation glaucoma in her left eye (OS). There were no intraoperative complications. Preoperatively, her best-corrected visual acuity (BCVA) was 0.6, and her intraocular pressure (IOP) was 25 mmHg with three antiglaucoma medications in the OS. On postoperative day 21, the IOP was 21 mmHg OS, and the filtration bleb had shrunk. A needling procedure was performed using a sharp 26-gauge needle to lower the IOP. On postoperative day 29, the BCVA was 0.02, and the IOP was 60 mmHg OS. Gonioscopy revealed no device tip in the anterior chamber, and peripheral anterior synechia was observed at the site of PFM insertion. Anterior segment optical coherence tomography showed a dislocated device in the subconjunctival space. On postoperative day 35, the dislocated PFM was removed, and a new device was inserted. Following the reoperation, no further complications were observed, and bleb formation was obtained. In conclusion, like other glaucoma filtering surgeries, PFM may require postsurgical needling procedures. Needling procedures may cause PFM dislocation and IOP rise, resulting in the requirement for further IOP-reducing procedures.

PRESERFLO ™ MicroShunt versus trabeculectomy: 1-year results on efficacy and safety

PURPOSE

To compare the efficacy and safety of the PRESERFLO™ MicroShunt versus trabeculectomy in patients with primary open-angle glaucoma (POAG) after one year.

PATIENTS AND METHODS

Institutional prospective interventional cohort study comparing eyes with POAG, which had received the PRESERFLO™ MicroShunt versus trabeculectomy. The MicroShunt group was matched with the trabeculectomy group for age, known duration of disease, and number and classes of intraocular pressure (IOP) lowering medications to have similar conjunctival conditions. The study is part of the Dresden Glaucoma and Treatment Study, using a uniform study design, with the same inclusion and exclusion criteria, follow-ups and standardized definitions of success and failure for both procedures.

PRIMARY OUTCOME MEASURES

mean diurnal IOP (mdIOP, mean of 6 measurements), peak IOP, and IOP fluctuations.

SECONDARY OUTCOME MEASURES

success rates, number of IOP lowering medications, visual acuity, visual fields, complications, surgical interventions, and adverse events.

RESULTS

Sixty eyes of 60 patients, 30 in each group, were analyzed after 1-year follow-ups. Median [Q25, Q75] mdIOP (mmHg) dropped from 16.2 [13.8-21.5] to 10.5 [8.9-13.5] in the MicroShunt and from 17.6 [15.6-24.0] to 11.1 [9.5-12.3] in the trabeculectomy group, both without glaucoma medications. Reduction of mdIOP (P = .596), peak IOP (P = .702), and IOP fluctuations (P = .528) was not statistically significantly different between groups. The rate of interventions was statistically significantly higher in the trabeculectomy group, especially in the early postoperative period (P = .018). None of the patients experienced severe adverse events.

CONCLUSION

Both procedures are equally effective and safe in lowering mdIOP, peak IOP and IOP fluctuations in patients with POAG, one year after surgery.

CLINICAL TRIAL REGISTRATION

NCT02959242.

Clinical Outcomes and Cost Analysis of PreserFlo versus Trabeculectomy for Glaucoma Management in the United Kingdom

PURPOSE

Clinical evaluation and cost analysis of mitomycin-C-augmented PreserFlo MicroShunt versus trabeculectomy.

DESIGN

Retrospective cohort study across 3 teaching hospitals.

PARTICIPANTS

A total of 134 consecutive eyes of 129 patients (70 undergoing MicroShunt, 64 trabeculectomy).

METHODS

Primary and secondary glaucoma cases with uncontrolled intraocular pressure (IOP) were included. Neovascular glaucoma and surgery combined with cataract extraction were excluded. The cost analysis used results from the clinical study to estimate operative costs (equipment and staff costs) and postoperative costs (follow-up visits, nonglaucoma medications, and postoperative procedures) per eye for PreserFlo and trabeculectomy.

MAIN OUTCOME MEASURES

The primary clinical outcome measure was surgical failure (defined as IOP > 21 mmHg or < 20% reduction from baseline, IOP ≤ 5 mmHg, reoperation, or loss of light perception) or qualified and complete success (with or without medication) at 18 months. Secondary measures were IOP, glaucoma medications, visual acuity, mean deviation, time to cessation of steroid drops, complications, surgical time, follow-up visits, postoperative interventions, and reoperations. The cost analysis evaluated costs of PreserFlo compared with trabeculectomy.

RESULTS

Baseline characteristics were similar, except for more non-White patients in the trabeculectomy group (51% Black and Asian vs. 32% MicroShunt, P = 0.02) and more cases with prior ab externo glaucoma surgery in the MicroShunt group (19% vs. 3% in the trabeculectomy group, P = 0.004). Overall, 59% of eyes had primary open-angle glaucoma. Mean follow-up was 19.9 months for both groups. At 18 months, surgical failure was 25% for MicroShunt compared with 35% for trabeculectomy (P = 0.18). Failure in MicroShunt cases was due to inadequate IOP reduction (84%) or reoperation for glaucoma (16%). Failure in trabeculectomy cases was due to inadequate IOP reduction (58%), persistent hypotony (29%), or reoperation for glaucoma (13%). Combined blebitis and endophthalmitis rate was 1.4% for MicroShunt and 3.1% for trabeculectomy. Cost analysis showed a savings of £245 to £566 per eye in the MicroShunt group, driven mostly by reduced postoperative procedures and follow-up visits. This is in contrast to prior randomized controlled trial data reporting the incremental cost of $2058 of PreserFlo over trabeculectomy.

CONCLUSIONS

Our experience of introducing PreserFlo MicroShunt surgery showed it was safer than trabeculectomy and is a cost-saving and effective option that offers potential to free up highly limited National Health Service resources.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Subconjunctival filtration in evolution: current evidence on MicroShunt implantation for treating patients with glaucoma

BACKGROUND

Although traditional surgical procedures for glaucoma (such as trabeculectomy and tube-shunt implantation) can significantly reduce intraocular pressure (IOP), they are associated with numerous complications, some of which are vision-threatening, or involve prolonged recovery or a highly intensive postoperative course. Micro-invasive glaucoma surgery (MIGS) procedures have shown better safety but reduced efficacy in achieving target IOP. Combinations of these methods have led to the development of subconjunctival micro-invasive procedures with safety comparable to traditional surgery and greater efficacy than minimally invasive methods. This review describes the use of one of these devices, the poly(styrene-block-isobutylene-block-styrene) (SIBS)-based PreserFlo MicroShunt (Santen, Emeryville, CA), in the surgical treatment of patients with glaucoma.

MAIN TEXT

The MicroShunt is an 8.5-mm tube made of an inert polymer with no endplate, an internal diameter of 70 μm, and fins intended to prevent peritubular flow and anchor the device within the sclera to prevent proximal migration into the eye. Following ab externo implantation, the tube provides a conduit for flow of aqueous humor from the anterior chamber into the subconjunctival/sub-Tenon space. Clinical trials to date have shown that, when paired with mitomycin C (MMC) treatment, MicroShunt implantation significantly reduced both IOP and the number of glaucoma medications. These IOP-lowering results were found both when surgery was performed alone and with phacoemulsification. The MicroShunt also showed a safety profile comparable to that of traditional filtering surgery.

CONCLUSIONS

The MicroShunt and other novel subconjunctival procedures have shown substantial IOP reductions while mitigating hypotony-related complications. MMC, which modulates fibrosis and scarring postoperatively, is essential to surgical success. Randomized, long-term clinical trials will further clarify the role of controlled micro-incisional device-assisted ab externo glaucoma filtering surgery in long-term glaucoma management.

Short-term safety and efficacy of Preserflo™ Microshunt in glaucoma patients: a multicentre retrospective cohort study

BACKGROUND/AIMS

To evaluate 1-year success rates and safety profile of Preserflo™ Microshunt in glaucoma patients.

METHODS

Retrospective multicentre cohort study of 100 consecutive eyes (91 patients) from four tertiary-referral glaucoma centres. Four intraocular pressure (IOP) criteria were defined: A: IOP ≤ 21 mmHg+IOP reduction ≥20% from baseline; B: IOP ≤ 18 mmHg+IOP reduction ≥20%; C: IOP ≤ 15 mmHg+IOP reduction ≥25%; D: IOP≤12 mmHg+IOP reduction ≥30%. Success was defined as qualified or complete based on whether reached with or without medication. Primary outcome was success according to the above criteria. Secondary outcomes included: IOP, best-corrected visual acuity (BCVA), medication use, complications, postoperative interventions, and failure-associated factors.

RESULTS

Qualified and complete success rates (95% CI) at 12 months were 74%(66-83%) and 58%(49-69%) for criterion A, 72%(63-82%) and 57%(48-68%) for B, 52%(43-63%) and 47%(38-58%) for C, 29%(21-40%) and 26%(19-36%) for D. Overall median (interquartile range (IQR)) preoperative IOP decreased from 21.5(19-28) mmHg to 13(11-16) mmHg at 12 months. BCVA was not significantly different up to 12 months (p = 0.79). Preoperative median (IQR) number of medications decreased from 3 (2-3) to 0 (0-1) at 12 months. Twelve eyes underwent needling, five surgical revision and one device removal due to corneal oedema. There were no hypotony-related complications. Non-Caucasian ethnicity was the only risk factor consistently associated with increased failure.

CONCLUSIONS

Preserflo™ Microshunt is a viable surgical option in glaucoma patients, with reasonable short-term success rates, decreased medications use, excellent safety profile, smooth postoperative care, and rapid learning curve. Success rates for the most stringent IOP cutoffs were modest, indicating that it may not be the optimal surgery when very low target IOP is required.

Expert Consensus on the Use of the PRESERFLO™ MicroShunt Device in the Treatment of Glaucoma: A Modified Delphi Panel

INTRODUCTION

The implantation of the PRESERFLO™ MicroShunt (PMS) device has been shown to significantly lower increased intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG). However, guidelines on best practice for patient selection and pre-/peri-/postoperative care management are lacking. The aim of this modified Delphi panel was to achieve expert consensus on the role of the PMS to treat patients with glaucoma in Europe.

METHODS

Twelve European glaucoma surgeons experienced with the PMS procedure participated in a three-round modified Delphi panel. A targeted literature review and expert steering committee guided round 1 questionnaire development. Consensus was set at a pre-defined threshold of at least 70% of panellists selecting 'Strongly disagree'/'Disagree' or 'Strongly agree'/'Agree' for six-point Likert scale questions, or at least 70% selecting the same option for multiple-choice questions. Questions not reaching consensus were restated/revised for the next round, following guidance from free-text responses/scoping questions.

RESULTS

Consensus was achieved for 60.3% (n = 38/63), 60.0% (n = 18/30), and 100.0% (n = 11/11) of Likert/multiple-choice questions in rounds 1, 2, and 3, respectively. There was agreement that the PMS procedure is effective at reducing IOP in patients with high-tension POAG (greater than 21 mmHg). Although surgical techniques may vary slightly, consensus was reached on several points, including the importance of posterior application of mitomycin C (MMC). Panellists agreed that the PMS postoperative follow-up appointment schedule is reasonably predictable and mostly characterised by fewer visits than with trabeculectomy, particularly in the early phase. Although panellists agreed that combined cataract/PMS surgery and the use of non-MMC wound-healing modulators/antifibrotics during the procedure are possible, further data are needed to determine efficacy.

CONCLUSION

The expert consensus reached in this panel will help inform best practice guidelines in the treatment of patients with glaucoma in Europe. Panellists also highlighted key areas for future research to improve understanding of the PMS in the treatment algorithm of glaucoma.

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.

Insertion of a Preserflo microshunt inside a non-valved glaucoma shunt to treat late-onset hypotony

We present a case of advanced glaucoma with previously failed trabeculectomy who underwent a Baerveldt tube (BVT) insertion, with initial success. However, 9 months post BVT insertion he developed profound clinically significant hypotony. Two attempts at controlling this with suture exchange led to episodes of significant ocular hypertension, followed by hypotony each time. We describe a technique of using a cut segment of the novel, polystyrene-block-isobutylene-block- styrene (SIBs) based Preserflo Microshunt (Santen Inc., Miami, FL) inserted into the tip of a BVT to control late onset hypotony with success. IOP at 6 weeks was 12mmHg on two drops with complete resolution of the choroidal maculopathy.

PRESERFLO™ MicroShunt versus trabeculectomy: first results on efficacy and safety

PURPOSE

To report efficacy and safety outcomes of the PRESERFLO™ MicroShunt compared with trabeculectomy, the current gold-standard treatment for advanced glaucoma, in the early and intermediate postoperative period.

METHODS

Institutional prospective interventional cohort study of primary open-angle glaucoma (POAG) patients scheduled for the PRESERFLO™ MicroShunt. The comparison group were POAG patients who had had received trabeculectomy and were matched for age, known duration of disease, number and classes of intraocular pressure (IOP)-lowering medications to ensure a similar conjunctival condition. The study is part of the Dresden Glaucoma and Treatment Study (DGTS), was not randomized, but used a uniform study design, with the same inclusion and exclusion criteria as well as standardized definitions of success and failure.

MAIN OUTCOME MEASURES

mean diurnal IOP (mdIOP, mean of 6 measurements), diurnal peak IOP, diurnal IOP fluctuations, glaucoma medical therapy, success rates, visual acuity, visual fields, surgical complications and interventions, and severe adverse events.

RESULTS

Fifty-two eyes of 52 patients, 26 in each group, were analysed. At 6 months, median [Q25, Q75] mdIOP was 10.8 [9.5-12.2] mmHg in the microshunt and 10.3 [7.6-11.8] mmHg in the trabeculectomy group. Reduction in mdIOP (p = 0.458), peak diurnal IOP (p = 0.539), and median diurnal fluctuation (p = 0.693) was not statistically significantly different between groups. The rate of interventions was statistically significantly higher in the trabeculectomy compared with the microshunt group (p = 0.004). None of the patients experienced severe adverse events.

CONCLUSION

Both procedures are equally effective and safe in lowering mdIOP in patients with POAG. Because the microshunt is less invasive with less follow-up and interventions needed postoperatively, it might be recommended earlier in the treatment of glaucoma.

Retrospective Analysis of 12 Months Glaucoma Implant Efficacy: XEN45 and PreserFlo Microshunt

PURPOSE

Several new implant devices have recently been introduced to glaucoma surgery using various techniques for reducing intraocular pressure (IOP). Two implants introduced during the past couple of years, XEN45 and PreserFlo Microshunt, are both designed to control subconjunctival filtration. There are two Swiss multicenter studies that collected the data retrospectively to analyze the efficacy and safety of these two devices separately. In this study, we report the analysis of the combined data subset from the University Hospital of Basel.

SUBJECTS AND METHODS

The XEN45 implantation technique was introduced to Basel University Hospital in 2016 and PreserFlo Microshunt in 2018. Sixty operated patients, thirty in each group, were operated on by one surgeon, clinically followed up, and their data retrospectively analyzed from medical records. Only standalone procedures, without combined phacoemulsification, were considered in this analysis; the lens status, however, was neither an inclusion nor an exclusion criterion. Further inclusion criteria were the diagnosis of open-angle glaucoma, no previous glaucoma surgery, other than laser trabeculoplasty, and complete medical records during the 12 months of follow-up. IOP reduction during a 12-month postoperative period was the primary outcome measure as well as the number of IOP reducing drugs. The number of subsequent surgical interventions and complications/adverse events are descriptively reported.

RESULTS

Patient age, gender, ophthalmological diagnosis, and initial preoperative IOP were well balanced between the two groups. Postoperative IOP course was comparable between the two methods for the first 12 months. IOP measurements were taken preoperatively and then on the first postop day, week 1, month 1, and months 3, 6, and 12 for the PreserFlo Microshunt vs. XEN45 (mmHg): 23.6 vs. 24.9, 9.0 vs. 8.9, 11.4 vs. 10.6, 13.0 vs.18.3, 16.8 vs.15.1, 15.9 vs.15.0, and 15.4 vs.14.5, respectively. IOP reducing medications were also comparable between the two groups. The study showed that subsequent interventions were more frequent in the XEN45 (13) than in the PreserFlo Microshunt group (7).

CONCLUSION

Both methods demonstrate satisfactory IOP control within a 12-month postoperative period with practically no serious adverse events/complications, but with relatively high numbers of subsequent interventions (needlings), particularly in the XEN45 group.

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.

Association of the prolonged use of anti-glaucoma medications with the surgical failure of ab interno microhook trabeculotomy

PURPOSE

This study examined the perioperative factors affecting surgical success in ab interno microhook trabeculotomy (μTLO).

METHODS

A total of 146 consecutive patients who underwent μTLO were included in this retrospective study. We performed Cox proportional hazard modelling by setting surgical success at 1 year as an objective variable. The explanatory variables included age, sex, glaucoma type, preoperative intraocular pressure (IOP), glaucoma drug score, mean deviation (MD) of the Humphrey visual field test, duration of glaucoma drug use, antithrombotic drug use, combined cataract surgery, incision range and diabetes mellitus. Additionally, we performed 1:1 matching using propensity score analysis and compared the perioperative parameters between durations of glaucoma drug use of <4.5 years and ≥ 4.5 years (50 patients each). We defined surgical success as satisfaction of all three criteria: IOP 5-21 mmHg, IOP reduction of ≥20% from the preoperative IOP and no additional glaucoma surgery.

RESULTS

The Cox proportional hazard model revealed that a longer duration of anti-glaucoma medication was significantly associated with surgical failure. Propensity score matching analysis showed that the <4.5-year users of anti-glaucoma drugs had significantly higher success rates than the ≥4.5-year users (72% versus 52%; p = 0.04).

CONCLUSIONS

The prolonged use of multiple glaucoma drugs adversely affected the outcome of μTLO at least at 1 year postoperatively.

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.

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.

Comparison of subconjunctival microinvasive glaucoma surgery and trabeculectomy

PURPOSE

To assess surgical success and the post-operative development of intraocular pressure between XEN45^® gelstent, Preserflo^® MicroShunt and trabeculectomy with mitomycin C.

METHODS

Data from 105 eyes from 105 patients of matched cases with refractory open-angle glaucoma, who underwent surgery between January 2019, and August 2020, were evaluated. Patients underwent either stand-alone XEN gelstent insertion with Mitomycin C, stand-alone Preserflo with Mitomycin C or trabeculectomy with Mitomycin C. The primary outcome was the proportion of complete surgical success at 6 months post-operatively (i.e. intraocular pressure between 5mmHg and 18mmHg, no revision surgery, no loss of light perception and no post-operative pharmaceutical antiglaucomatous treatment). The reduction of intraocular pressure after 6 months, the classes of antiglaucomatous medication used post-operatively, best-corrected visual acuity, spherical refractive errors and astigmatism were assessed as secondary outcomes.

RESULTS

We included 35 eyes in each group. After 6-month follow-up, complete success was 73.5% [95%-CI: 57.9%-89.2%] in the trabeculectomy group, 51.4% [95%-CI: 34.0%-68.8%] in the XEN group and 74.2% [95%-CI: 57.9%-90.5%] in the Preserflo group (p = 0.08). Regarding secondary outcomes, the reduction of intraocular pressure was 12.1 ± 7.9 mmHg in the trabeculectomy group and was thereby 5.8 [95%-CI: 2.2-9.6] mmHg greater compared with the XEN group (p < 0.001) and 4.8 [95%-CI: 0.9-8.7] mmHg higher than the Preserflo group (p = 0.01).

CONCLUSIONS

No statistically significant differences were found between trabeculectomy, XEN45^® gelstent implantation and Preserflo^® MicroShunt implantation regarding surgical success after 6 months. Yet reduction in intraocular pressure was significantly higher in the trabeculectomy group. However, all three interventions resulted in sufficiently low post-operative intraocular pressure and may therefore be considered individually for glaucoma treatment.

Preliminary results of Preserflo Microshunt versus Preserflo Microshunt and Ologen implantation

PURPOSE

To report preliminary 6-month results on the use of the Preserflo Microshunt implant with and without Ologen in 50 pseudophakic eyes with moderate to advanced primary open-angle glaucoma (POAG).

METHODS

Fifty pseudophakic eyes underwent ab externo Preserflo Microshunt implantation. Data was gathered retrospectively and two groups were then created, group A with application of MMC 0.2 mg/ml and group B with MMC 0.2 mg/ml and Ologen collagen matrix (OCM) implantation. Absolute success was regarded as the percentage of eyes achieving: a) 5 ≤ intraocular pressure (IOP) ≤ 13 mmHg, b) 5 ≤ IOP ≤ 16 mmHg, and c) 5 ≤ IOP ≤ 21 mmHg without additional medication or surgery and qualified success was regarded as the percentage of eyes achieving a) IOP ≤ 13 mmHg, b) IOP ≤ 16 mmHg, and c) IOP ≤ 21 mmHg with or without medication. Evaluation was performed using a log-rank Kaplan-Meier test. A scatterplot analysis presented the treatment effect data of all eyes with a minimum of 20% IOP reduction per case. Failure was defined as requiring additional surgery, IOP greater than 21 mmHg with or without medication and failure to reach 20% IOP reduction.

RESULTS

Mean postoperative IOP was significantly lower in both groups. IOP decreased by 49.06% in group A and by 53.01% in group B at 6 months (P < 0.88), respectively. Medication use was lower in both groups (Wilcoxon test, P < 0.001). The absolute and qualified success rates were not statistically significant between the groups (all P > 0.05). Cumulative IOP results per case were not statistically different in group A compared with group B. One revision surgery in group A (4% failure rate) and three in group B (12% failure rate) were performed.

CONCLUSIONS

Both groups showed equal results in terms of cumulative and mean IOP reduction, medication reduction as well as in absolute and qualified success rates. No significant difference was found in any parameters tested between Preserflo Microshunt with MMC 0.2 mg/ml and with or without OCM implantation at 6 months. Long-term follow-up is required to further evaluate this data.

Intraocular Pressure-Lowering Effects of Trabeculectomy Versus MicroShunt Insertion in Rabbit Eyes

Purpose

To compare the surgical results of PRESERFLO MicroShunt (MicroShunt) insertion and trabeculectomy in rabbit eyes.

Methods

Trabeculectomy or MicroShunt insertion was performed on the eyes of Japanese white rabbits. Intraocular pressure (IOP) was measured on conscious rabbits using a rebound tonometer for up to 12 weeks after surgery. Filtering bleb appearance was evaluated. Scarring in the filtering bleb was assessed by immunohistochemical analyses. The change in mRNA expression in the conjunctiva was evaluated using RNA sequence analyses.

Results

The preoperative IOP of the operative eye did not differ significantly between trabeculectomy (11.6 ± 1.0 mmHg, n = 10) and MicroShunt insertion (12.6 ± 1.3 mmHg, n = 10). In both groups, the IOP of the operative eye was significantly lower than that of the contralateral eye at one day postoperatively, which continued until 12 weeks after surgery. The peak differences in IOP were −8.4 ± 3.0 (trabeculectomy) and −8.1 ± 2.1 mmHg (MicroShunt) at two weeks after surgery; no significant differences were observed in IOP reduction between the groups. Appearance and immunohistochemical analyses of the filtering bleb showed no significant difference between the groups. Moreover, RNA sequence analysis results showed no difference between the groups in mRNA expression fluctuations.

Conclusions

Postoperative IOP, bleb appearance, and immunohistochemical analysis results were similar in the trabeculectomy and MicroShunt groups, indicating that MicroShunt insertion is as effective as trabeculectomy in lowering IOP.

Translational Relevance

Comparison of surgical procedures using animal models has made it possible to predict clinical efficacy and safety.

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.

Safety and Effectiveness of the PRESERFLO® MicroShunt in Primary Open-Angle Glaucoma: Results from a 2-Year Multicenter Study

OBJECTIVE

To assess the safety and effectiveness of the PRESERFLO® MicroShunt (formerly InnFocus MicroShunt®) in patients with primary open-angle glaucoma (POAG).

DESIGN

The MicroShunt, a controlled ab-externo glaucoma filtration surgery device, was investigated in a 2-year, multicenter, single-arm study.

PARTICIPANTS

Eligible patients were aged 18-85 years with POAG inadequately controlled on maximal tolerated medical therapy with intraocular pressure (IOP) ≥18 and ≤35 mmHg and/or where glaucoma progression warranted surgery.

INTERVENTION

The MicroShunt was implanted as a standalone procedure with adjunctive use of topical Mitomycin C (MMC; 0.2-0.4 mg/mL) for 2-3 minutes.

MAIN OUTCOME MEASURES

The primary effectiveness outcome was IOP reduction and success (not requiring reoperation or pressure failures [IOP >21 mmHg and <20% reduction in IOP]) at year 1. Additional endpoints at year 2 included IOP reduction, success, glaucoma medications, adverse events (AEs), and reoperations. Results are reported in the overall population, and subgroups of patients receiving 0.2 or 0.4 mg/mL MMC.

RESULTS

In 81 patients, mean (± standard deviation [SD]) IOP reduced from 21.7±3.4 mmHg at baseline to 14.5±4.6 mmHg at year 1 and 14.1±3.2 mmHg at year 2 (P<0.0001). Overall success (with and without supplemental glaucoma medication use) at year 1 was 74.1%. Mean (± SD) number of medications decreased from 2.1±1.3 at baseline to 0.5±0.9 at year 2 (P<0.0001), 73.8% of patients were medication free. Most common non-serious AEs were increased IOP requiring medication and/or selective laser trabeculoplasty (25.9%) and mild-to-moderate keratitis (11.1%). There were 6 (7.4%) reoperations and 5 (6.2%) needlings by year 2. In an analysis (post-hoc) according to MMC concentration, overall success was 78.1% (0.2 mg/mL) and 74.4% (0.4 mg/mL; P=0.710). In the 0.2 and 0.4 mg/mL MMC groups, 51.9% and 90.3% of patients were medication-free, respectively (P=0.001). There was a trend towards lower IOP and higher medication reduction in the 0.4 mg/mL MMC subgroup.

CONCLUSIONS

In this study, mean IOP and glaucoma medication reductions were significant and sustained over 2 years post-surgery. No long-term, sight-threatening AEs were reported. Further studies may confirm potential risk/benefits of higher MMC concentration.

Effect of valproic acid on functional bleb morphology in a rabbit model of minimally invasive surgery

Purpose

To determine the effect of valproic acid (VPA) on bleb morphology and scar characteristics in a rabbit model of minimally invasive glaucoma surgery (MIGS).

Methods

Nine New Zealand white rabbits were subjected to MIGS with intraoperative implantation of the PreserFlo MicroShunt. Rabbits were then administered with subconjunctival injections of phosphate buffered saline (PBS) (n=4) or with VPA (n=5). Bleb morphology was examined by slit-lamp biomicroscopy and in vivo confocal microscopy. Postoperative day 28 tissues were examined by immunohistochemical evaluation and label-free multiphoton microscopy to visualise the collagen matrix, by terminal deoxynucleotidyl transferase dUTP nick-end labelling assay and immunofluorescent labelling for Ki67 expression to detect apoptosis and cell growth, and by real-time quantitative PCR to measure Col1a1, Fn, and Smad6 transcript expression.

Results

VPA-treated blebs were detectable on day 28, while the PBS-treated blebs were not detectable by day 14. VPA-treated blebs were diffuse, extended posteriorly with near normal conjunctival vascularity and featured a combination of reticular/blurred stromal pattern with evidence of relatively large stromal cysts. Instead of the deposition of thick, disorganised collagen fibres characteristic of the PBS bleb, the VPA bleb contained conspicuously thinner collagen fibres which were associated with similarly thinner fibronectin fibres. In corroboration, Col1a1 and Fn mRNA expression was reduced in the VPA blebs, while increased Smad6 expression implicated the disruption of the transforming growth factor beta pathway. Apoptosis and cell growth profiles appeared similar with both treatments.

Conclusions

The results support the application of VPA to enhance bleb morphology associated with good bleb function in MIGS with no apparent cytotoxicity.

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.

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.

Ethics of Glaucoma Widgets

How to cite this article: Dada T, Ramesh P, Sethi A, et al. Ethics of Glaucoma Widgets. J Curr Glaucoma Pract 2020;14(3):77–80.

Chronic Granulomatous Inflammation after CyPass® Implantation

A 65-year-old patient suffering from pseudoexfoliation glaucoma and multiple previous surgeries at the right eye underwent CyPass® explantation 19 months after CyPass® Micro-Stent implantation due to chronic inflammation in the an-terior chamber. Histologically, a foreign body granuloma around and in the CyPass® implant was found. We conclude that patients with previous multiple glaucoma surgeries should not undergo CyPass® Micro-Stent implantation.

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.

Minimally Invasive Glaucoma Surgery: Where Is the Evidence?

PURPOSE

The last decade has witnessed an unprecedented growth in glaucoma treatment options through the introduction of minimally invasive glaucoma surgeries (MIGS). The aim of the present review is to provide an understanding of the currently available MIGS and to examine what data are currently available to guide treatment choice.

DESIGN

Meta-analysis and systematic review of randomized and non-randomized control trials.

METHODS

Out of 2567 articles identified, a total of 77 articles were retained for analysis, including 28 comparative studies and 12 randomized control trials. Overall, 7570 eyes were included. When data permitted, the weighted mean difference in intraocular pressure reduction was calculated for comparison purposes.

RESULTS

Weighted mean intraocular pressure reductions from all analyzed studies were: 15.3% (iStent), 29.1% (iStent inject), 36.2% (ab interno canaloplasty), 34.4% (Hydrus), 36.5% (gonioscopically-assisted transluminal trabeculotomy), 24.0% (trabectome), 25.1% (Kahook dual blade), 30.2% (Cypass), 38.8% (XEN), and 50.0% (Preserflo).

CONCLUSIONS

One of the advantages of the heterogenous range of available MIGS options is the chance to tailor therapy in an individualized manner. However, high-quality data are required to make this choice more than an educated guess. Overall, this review confirms the efficiency of assessed MIGS compared with standalone phacoemulsification, but it highlights that only few studies compare different MIGS techniques and even fewer assess MIGS against criterion standard treatments. Current evidence, while non-negligible, is mostly limited to heterogenous nonrandomized studies and uncontrolled retrospective comparisons, with few quality randomized control trials. We suggest that future research should be comparative and include relevant comparators, standardized to report key outcome features, long-term to assess sustainability and late complications, and ideally randomized.

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.

Translating Minimally Invasive Glaucoma Surgery Devices

Glaucoma is the leading cause of irreversible blindness with over 70 million people affected worldwide. The surgical management of glaucoma aims to lower intraocular pressure by increasing aqueous outflow facility. The latest manufacturing techniques have allowed for the development of a number of novel implantable devices to improve safety and outcomes of glaucoma surgery. These are collectively referred to as minimally invasive glaucoma surgery (MIGS) devices and are among the smallest devices implanted in the human body. This review discusses the design criterion and constraints as well as the user requirements for MIGS devices. We review how recent devices have attempted to meet these challenges and give our opinion as to the necessary characteristics for the development of future devices.

Micro-invasive glaucoma surgery - an interventional glaucoma revolution

The glaucoma surgical landscape has changed dramatically over the last decade with the introduction and integration of micro-invasive glaucoma surgery (MIGS) techniques. These modalities target physiologic outflow pathways or optimize previously utilized glaucoma surgical methods in order to deliver safety, efficacy, and individualized care to the patient. MIGS techniques can be classified based on anatomical location as well as method of intraocular pressure (IOP) reduction. This review will focus on MIGS optimizing the conventional outflow pathway via intervention at Schlemm’s canal, MIGS optimizing the uveoscleral outflow pathway via suprachoroidal shunting, and MIGS optimizing the transscleral or subconjunctival outflow pathway which has long been utilized by glaucoma surgeons performing traditional filtration procedures. The wide array of currently available MIGS modalities can be staggering to the glaucoma care provider, but an understanding of the landscape and the large classes of interventional strategies can allow for clinical decision making based on the specifics of the patient’s needs and the pathophysiology of their disease.

Microinvasive Glaucoma Surgery: An Evidence-Based Assessment

Introduction

The advent of Microinvasive Glaucoma Surgery (MIGS) offers a novel approach in the treatment of glaucoma with the number of procedures developing at an exciting pace.

Areas Covered

MIGS procedures aim to lower intraocular pressure (IOP) via four mechanisms: (1) increasing trabecular outflow, (2) increasing outflow via suprachoroidal shunts, (3) reducing aqueous production, and (4) subconjunctival filtration. A comprehensive search for published studies for each Microinvasive Glaucoma Surgery (MIGS) device or procedure was undertaken using the electronic database PubMed. Search terms included 'minimally invasive glaucoma surgery', 'microincisional glaucoma surgery', and 'microinvasive glaucoma surgery'. A manual search for each device or procedure was also performed. After review, randomized control trials and prospective studies were preferentially included.

Expert Opinion

These procedures offer several benefits: an improved safety profile allowing for intervention in earlier stages of glaucoma, combination with cataract surgery, and decreased dependence on patient compliance with topical agents. Established MIGS procedures have proven efficacy and more recent devices and procedures show promising results. Despite this, further study is needed to assess the long term IOP-lowering effectiveness of these procedures. Particularly, rigorous study with more randomized control trials and head-to-head comparisons would allow for better informed clinical and surgical decision-making. MIGS offers new solutions for glaucoma treatment.