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

Intraoperative OCT to check the correct postimplant position of PreserfloTM

INTRODUCTION

This study was designed to examine the capacity of intraoperative optical coherence tomography (OCT) to predict the postimplant position of the glaucoma drainage device PreserfloTM.

METHODS

13 eyes (mean age 65.42 (14.89) years) underwent PreserfloTM (Santen, Osaka, Japan) placement. Before surgery, participants were subjected to a comprehensive ophthalmic examination (intraocular pressure (IOP), cup to disk ratio (C/D), visual field, OCT, endothelial cell count). Anterior segment OCT scans were obtained intraoperatively using a Rescan 700 OCT system (Carl Zeiss Meditec, Inc., Oberkochen, Germany). One day postsurgery, anterior segment OCT using the Spectralis OCT (Heidelberg Engineering GmbH) was performed in a sitting position to capture the same chamber cross-section as before. The main outcome variables were tube-endothelium distance (T-E) and tube length (TL) in the anterior chamber measured using both OCT systems. Correlation between intraoperative and office measurements was examined through Pearson correlation (r) and intraclass correlation coefficients (ICC).

RESULTS

Mean intraoperative and in-office T-E were 625.26 (SD 366.60) versus 561.16 (SD 364.62) µm respectively (p = 0.540). Intraoperative and in-office anterior chamber TL were 1386 (SD 701.82) and 1433.91 (SD 713.55) µm, respectively (p = 0.029). Excellent correlation was observed between both sets of T-E (r = 0.992; p = 0.008) and TL (r = 0.984; p = 0.016) values. Both OCT systems showed good agreement yielding ICCs of 0.992 (p < 0.001) for T-E and 0.995 (p = 0.001) for TL.

DISCUSSION

Excellent correlation was observed between our intraoperative and postoperative OCT measurements. These results support the usefulness of intraoperative OCT to confirm the correct position of an implanted PreserfloTM microshunt.

Efficacy, Confounders and Safety of the Preserflo Microshunt

BACKGROUND

Glaucoma is a leading cause of blindness worldwide. We evaluated the efficacy, confounders, and safety of the Preserflo Microshunt over a one-year follow-up period.

METHODS

In this retrospective monocentric study, 111 eyes were evaluated. 83 eyes had primary open angle glaucoma, and 28 eyes secondary open angle glaucoma. Intraocular pressure (IOP), visual acuity, number of glaucoma medications, complications, and reoperations were evaluated postoperatively, at 1, 3, 6, 9, and 12 months. The influence of age, sex, type of glaucoma, previous surgery and lens status was also analysed. Bleb revision was indicated if corrected IOP exceeded 18 mmHg.

RESULTS

Intraocular pressure significantly decreased from 24.50 ± 8.94 to 14.62 ± 4.86 mmHg (4 - 32 mmHg; p < 0.001), the number of medications from 3.19 ± 1.14 to 0.98 ± 1.39 (0 - 4; p < 0.001). Confounders of interest did not affect efficacy. Bleb revision was performed in 22.5% of eyes and a cyclophotocoagulation was performed in 9.9% of eyes. Complete surgical success (IOP ≤ 17 mmHg, IOP reduction ≥ 20%, without medication) was achieved in 36.9% (n = 41) and qualified success (with medication) in 51.4% (n = 57) of eyes. Transient hypotension (≤ 5 mmHg) occurred in 19.8% after primary implantation and in 1.8% after bleb revision (duration ≤ 3 months).

CONCLUSION

To date, the Preserflo Microshunt has demonstrated good efficacy and a low risk profile.

[Glaucoma Filtration Surgery - Bleb-forming Procedures]

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

Assessing the Impact of PRESERFLO MicroShunt on Intraocular Pressure in Porcine Eyes Ex Vivo Using Infusion Pump System

To evaluate the effectiveness of the PRESERFLO MicroShunt (PFM) in reducing intraocular pressure (IOP) ex vivo in porcine eyes using an infusion pump system and to simulate various IOP conditions, In this study, porcine eyes received increasing flows between 2 and 20 μL/min. IOP measurements were taken under conditions with and without the PFM [PFM (+) and PFM (-), respectively]. In the PFM (-) group, IOP increased from 7.4 mmHg to 46.3 mmHg as the flow rate increased from 2 μL/min to 20 μL/min. The rate of IOP reduction (%ΔIOP) rose with increasing flow rates, although the absolute IOP values achieved with the PFM insertion also increased. The correlation between IOPs in the PFM (-) conditions and the %ΔIOP was modeled as %ΔIOP = 22.4 Ln [PFM(-) IOP] - 41.7. According to this equation, IOP reduction by PFM insertion is 0% at IOPs of 6.4 mmHg or lower. IOP reductions of 10%, 20%, 30%, and 40% were observed when the pre-insertion IOPs were 10.1, 15.7, 24.6, and 38.4 mmHg, respectively. Achievable post-insertion IOP levels of ≤21 mmHg, ≤18 mmHg, ≤15 mmHg, and ≤12 mmHg corresponded to the initial IOPs of 33 mmHg, 26 mmHg, 20 mmHg, and 14.8 mmHg, respectively. In conclusion, the PFM effectively reduced IOP within a specific range of IOP values in an ex vivo experimental system. In clinical situations, the PFM is unlikely to be effective at low IOP levels. At higher levels, the PFM reduces IOP, but it may be insufficient to achieve the target IOP.

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.

Preserflo TM MicroShunt implantation combined with Ologen TM in primary and secondary glaucoma patients in a clinical setting

PURPOSE

This study aims to assess the effectiveness and safety of combining the Preserflo™ MicroShunt implant (MicroShunt) with a simultaneous Ologen™ implant in patients with glaucoma.

METHODS

We conducted a retrospective study on consecutive patients with medically uncontrolled glaucoma who underwent MicroShunt + Ologen implantation as a standalone procedure or in combination with phacoemulsification (combined procedure). Success was defined as achieving an intraocular pressure (IOP) of 6-15 mmHg at 18 months post surgery, with a preoperative IOP reduction of at least 20%, and without (complete success) or with (qualified success) the need for antiglaucoma medications. The primary endpoint was the success rate.

RESULTS

Forty-eight eyes from 47 patients were included, with 28 eyes (58.3%) undergoing the standalone procedure and 20 eyes (41.7%) undergoing the combined procedure. Overall, there was a significant reduction in preoperative IOP from 19.7 ± 5.8 mmHg to 11.4 ± 2.6 mmHg at 18 months ( P < 0.0001). In the standalone procedure group, preoperative IOP decreased from 21.5 ± 5.2 mmHg to 11.7 ± 2.5 mmHg ( P < 0.0001), and in the combined procedure group, preoperative IOP decreased from 17.1 ± 5.8 mmHg to 10.9 ± 2.7 mmHg ( P = 0.0002), with no significant difference between the two groups regarding final IOP. The mean number of antiglaucoma medications significantly decreased from 3.2 ± 1.1 to 0.3 ± 0.7 in the overall study population ( P < 0.0001). At 18 months, 40 eyes (83.3%) were classified as successful. Regarding safety, out of the total number of eyes, two (4.2%) experienced choroidal detachment without visual impairment, two (4.2%) had transient hyphema, one (2.1%) showed reactivation of a corneal herpetic ulcer, one (2.1%) had diplopia, and one (2.1%) exhibited a shallow anterior chamber during the first week.

CONCLUSION

The combination of Ologen™ and Preserflo™ MicroShunt, either alone or in conjunction with phacoemulsification, demonstrated a favorable profile in terms of IOP reduction and safety.

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.

PreserFlo Microshunt for the management of intraocular pressure elevation in iridocorneal endothelial syndrome

Purpose

To report on a case of angle-closure glaucoma secondary to iridocorneal endothelial (ICE) syndrome effectively managed with the PreserFlo Microshunt.

Observations

We report successful implantation of a PreserFlo Microshunt in a 57-year-old patient with secondary angle-closure glaucoma in the context of ICE syndrome. Following failure of medical therapy to adequately control intraocular pressure (IOP), the patient was consented for surgical intervention and underwent combined cataract surgery and PreserFlo Microshunt implantation. IOP at the last post-operative follow-up (5 months) was 12 mmHg with the patient on brinzolamide/timolol maleate (Azarga®). We report no complications in the post-operative period.

Conclusions and importance

The PreserFlo Microshunt may be a promising option for patients with ICE syndrome who fail medical therapy. Implantation of this device was well tolerated in the presented case.

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.

Minimally Invasive Glaucoma Surgery: Latest Developments and Future Challenges

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

Results of a modified ab-external trabeculectomy surgical technique in patients with open angle glaucoma

OBJECTIVE

Assess the safety and efficacy of a Modified Ab-externo Trabeculectomy surgical technique in controlling intraocular pressure (IOP) in open-angle glaucoma patients.

METHODS AND ANALYSIS

Patients diagnosed with primary or secondary open-angle glaucoma underwent this modified technique as the first filtering surgical treatment were included. The preoperative and final follow-up assessed IOP, hypotensive medications, the need for additional treatments, and early and late complications.

RESULTS

Forty-eight eyes of 38 patients were included. The mean age was 63.1 years (25-85 years), and the mean follow-up time was 35.3 months (range of 1147 months). The mean preoperative IOP was 25.21±3.48mmHg and 15.83±4.4mmHg by the follow-up end. Subsequent laser goniopuncture was performed on 14 eyes (29%) and needling in 4 eyes (8.4%). Complete success was achieved in 18 eyes (37.5%), qualified success in 17 (35.4%), and failed in 13 eyes (27.1%). Kaplan-Meier survival analysis shows a success rate of 81.7% at two years and 54.9% from year 4 to year 12. Multivariate analysis with generalized estimating equations (GEE) shows younger age as the main predictor for failure. Two eyes had choroidal detachment, three eyes progressed to cataracts that needed surgery, and five eyes had early bleb leaks.

CONCLUSIONS

This proposed technique is an effective surgical procedure for treating open-angle glaucoma with effective long-term IOP control and a low incidence of surgical complications and could be used in selected complex cases based on these results.

Electrical, Electromagnetic, Ultrasound Wave Therapies, and Electronic Implants for Neuronal Rejuvenation, Neuroprotection, Axonal Regeneration, and IOP Reduction

The peripheral nervous system (PNS) of mammals and nervous systems of lower organisms possess significant regenerative potential. In contrast, although neural plasticity can provide some compensation, the central nervous system (CNS) neurons and nerves of adult mammals generally fail to regenerate after an injury or damage. However, use of diverse electrical, electromagnetic and sonographic energy waves are illuminating novel ways to stimulate neuronal differentiation, proliferation, neurite growth, and axonal elongation/regeneration leading to various levels of functional recovery in animals and humans afflicted with disorders of the CNS, PNS, retina, and optic nerve. Tools such as acupuncture, electroacupuncture, electroshock therapy, electrical stimulation, transcranial magnetic stimulation, red light therapy, and low-intensity pulsed ultrasound therapy are demonstrating efficacy in treating many different maladies. These include wound healing, partial recovery from motor dysfunctions, recovery from ischemic/reperfusion insults and CNS and ocular remyelination, retinal ganglion cell (RGC) rejuvenation, and RGC axonal regeneration. Neural rejuvenation and axonal growth/regeneration processes involve activation or intensifying of the intrinsic bioelectric waves (action potentials) that exist in every neuronal circuit of the body. In addition, reparative factors released at the nerve terminals and via neuronal dendrites (transmitter substances), extracellular vesicles containing microRNAs and neurotrophins, and intercellular communication occurring via nanotubes aid in reestablishing lost or damaged connections between the traumatized tissues and the PNS and CNS. Many other beneficial effects of the aforementioned treatment paradigms are mediated via gene expression alterations such as downregulation of inflammatory and death-signal genes and upregulation of neuroprotective and cytoprotective genes. These varied techniques and technologies will be described and discussed covering cell-based and animal model-based studies. Data from clinical applications and linkage to human ocular diseases will also be discussed where relevant translational research has been reported.

The Development of a SIBS Shunt to Treat Glaucoma

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

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.

One-year surgical outcomes of the PreserFlo MicroShunt in glaucoma: a multicentre analysis

BACKGROUND/AIMS

To evaluate the efficacy and safety of the PreserFlo MicroShunt glaucoma device in a multicentre cohort study.

METHODS

All consecutive patients who received the microshunt with mitomycin-C (MMC) 0.4 mg/mL from May 2019 to September 2020 in three UK tertiary centres. Primary outcome at 1 year was a complete success, with failure defined as intraocular pressure (IOP) >21 mmHg or <20% reduction, IOP≤5 mmHg with any decreased vision on two consecutive visits, reoperation or loss of light perception vision. Secondary outcomes were IOP, best-corrected visual acuity, medications, complications, interventions and reoperations. We also performed subgroup analyses for severe glaucoma and assessed risk factors for failure.

RESULTS

104 eyes had 1-year follow-up. Complete and qualified success at 1 year were achieved in 51.9% (N=54) and 16.4% (N=17), respectively, and failure occurred in 31.7% (N=33). There was a significant reduction in IOP (mmHg) from preoperatively (23.4±0.8, N=104) to 12 months (14.7±0.6, N=104) (p<0.0001). Antiglaucoma medications also decreased from preoperatively (3.4±0.1, N=104) to 12 months (0.7±0.1, N=104) (p<0.0001). Multivariate analyses showed an association between higher mean deviation and failure (HR 1.055, 95% CI 1.0075 to 1.11, p=0.0227). Complications were hypotony (19.2%; N=20), choroidal detachments (10.6%; N=11), hyphaema (5.8%; N=6) and bleb leak (5.8%; N=6). Needling and 5-fluorouracil injections were performed in 12.5% (N=13) and 33.7% (N=35), respectively, and 11.5% (N=12) required revision surgery.

CONCLUSION

The PreserFlo MicroShunt with MMC 0.4 mg/mL showed an overall success rate of 68.3% at 1 year, and led to significant IOP and medication reduction with a low rate of adverse effects.

Magnetically actuated glaucoma drainage device for regulating intraocular pressure after implantation

The key risk factor for glaucoma is increased intraocular pressure (IOP). Glaucoma drainage devices implanted in the eye can reduce IOP and thus stop disease progression. However, most devices currently used in clinical practice are passive and do not allow for postsurgical IOP control, which may result in serious complications such as hypotony (i.e., excessively low IOP). To enable noninvasive IOP control, we demonstrate a novel, miniature glaucoma implant that will enable the repeated adjustment of the hydrodynamic resistance after implantation. This is achieved by integrating a magnetic microvalve containing a micropencil-shaped plug that is moved using an external magnet, thereby opening or closing fluidic channels. The microplug is made from biocompatible poly(styrene-block-isobutylene-block-styrene) (SIBS) containing iron microparticles. The complete implant consists of an SIBS drainage tube and a housing element containing the microvalve and fabricated with hot embossing using femtosecond laser-machined glass molds. Using in vitro and ex vivo microfluidic experiments, we demonstrate that when the microvalve is closed, it can provide sufficient hydrodynamic resistance to overcome hypotony. Valve function is repeatable and stable over time. Due to its small size, our implant is a promising, safe, easy-to-implant, minimally invasive glaucoma surgery device.

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.

Early post-operative anterior segment parameters modifications induced by PreserFlo MicroShunt in primary open-angle glaucoma

PURPOSE

The aim this study is to determine anterior chamber parameters variations induced by PreserFlo MicroShunt implantation, in the early post-operative days.

METHODS

This is a prospective observational study on 48 eyes undergoing PreserFlo MicroShunt implantation alone (n = 30) or combined with phacoemulsification (n = 18). Anterior chamber depth (ACD) and volume (ACV), central corneal thickness (CCT) and total corneal astigmatism (TCA) were evaluated pre-operatively, post-operatively at day-1 and at 1 week with the Pentacam tomography.

RESULTS

Intraocular pressure decreased significantly from 20.9 ± 4.0 to 8.0 ± 2.8 mmHg (p < 0.0001) and to 10.8 ± 3.7 mmHg (p = 0.0001) at day-1 and week-1, respectively. TCA varied significantly from baseline (1.5 ± 1.2 D) to both day 1 follow up (2.7 ± 1.9 D, p = 0.0003) and week 1 follow up (2.2 ± 1.6 D, p = 0.02). Nevertheless, only K1 showed a transient flattening at day 1, while K2 value didn't show any statistical variation in the early post-operative period. CCT value rose significantly at day 1 (547 ± 49 vs. 529 ± 32 µm at baseline, p = 0.04), but then returned toward pre-operative values at week 1 (537 ± 39 µm, p = 0.57). In contrast, ACD values changed insignificantly from 3.3 ± 0.9 to 3.7 ± 1.0 mm at day 1 (p = 0.21), and then stabilized at 3.4 ± 0.9 mm (p = 0.82) at week 1 follow up. ACV changed from 150.0 ± 36.2 to 159.5 ± 42.1 mm³ at day 1 (p = 0.58), and successively to 153.9 ± 37.9 mm³ at week 1 follow up (p = 0.96). The subgroup analysis in eyes undergoing standalone PreserFlo implantation didn't show significant changes in both ACD and ACV.

CONCLUSION

PreserFlo implantation minimizes the anterior chamber modifications generated by traditional filtering surgery, inducing low and transient corneal and biometric changes only in the very early postoperative period and insignificant changes to ACD and ACV, label of its safety and minimal invasiveness.

FP and EP2 prostanoid receptor agonist drugs and aqueous humor outflow devices for treating ocular hypertension and glaucoma

Prostaglandin (PG) receptors represent important druggable targets due to the many diverse actions of PGs in the body. From an ocular perspective, the discovery, development, and health agency approvals of prostaglandin F (FP) receptor agonists (FPAs) have revolutionized the medical treatment of ocular hypertension (OHT) and glaucoma. FPAs, such as latanoprost, travoprost, bimatoprost, and tafluprost, powerfully lower and control intraocular pressure (IOP), and became first-line therapeutics to treat this leading cause of blindness in the late 1990s to early 2000s. More recently, a latanoprost-nitric oxide (NO) donor conjugate, latanoprostene bunod, and a novel FP/EP3 receptor dual agonist, sepetaprost (ONO-9054 or DE-126), have also demonstrated robust IOP-reducing activity. Moreover, a selective non-PG prostanoid EP2 receptor agonist, omidenepag isopropyl (OMDI), was discovered, characterized, and has been approved in the United States, Japan and several other Asian countries for treating OHT/glaucoma. FPAs primarily enhance uveoscleral (UVSC) outflow of aqueous humor (AQH) to reduce IOP, but cause darkening of the iris and periorbital skin, uneven thickening and elongation of eyelashes, and deepening of the upper eyelid sulcus during chronic treatment. In contrast, OMDI lowers and controls IOP by activation of both the UVSC and trabecular meshwork outflow pathways, and it has a lower propensity to induce the aforementioned FPA-induced ocular side effects. Another means to address OHT is to physically promote the drainage of the AQH from the anterior chamber of the eye of patients with OHT/glaucoma. This has successfully been achieved by the recent approval and introduction of miniature devices into the anterior chamber by minimally invasive glaucoma surgeries. This review covers the three major aspects mentioned above to highlight the etiology of OHT/glaucoma, and the pharmacotherapeutics and devices that can be used to combat this blinding ocular disease.

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.

Efficacy and safety of the PreserFlo implant with mitomycin C in childhood glaucoma after previous failed glaucoma surgeries

PURPOSE

This study aims to evaluate the efficacy and safety of the PreserFlo MicroShunt (Santen, Osaka, Japan) in lowering intraocular pressure (IOP) in childhood glaucoma patients with previous failed glaucoma surgeries.

METHODS

This is a prospective case review of consecutive PreserFlo procedures performed in childhood glaucoma patients after failed surgeries. Age, sex, diagnosis, and previous glaucoma surgeries, as well as visual acuity, IOP, and treatment in the preoperative visit and all follow-up visits were collected. Outcome measures included IOP reduction from baseline, mean IOP change from baseline at month 6, medication use at 6 months, complications, adverse events, and need for further procedures.

RESULTS

Fourteen patients were included, 8 (57%) males and 6 (43%) females; the mean age was 27.5 ± 13.5 years. Nine patients (64%) had at least two trabeculectomies, and 6 patients (43%) had at least one trabeculectomy and a glaucoma drainage implant. The mean IOP change from baseline was 11.3 ± 4.9 mmHg at 12 months. At 12 months, 12 patients (86%) presented ≥ 20% IOP lowering from baseline, and 11 patients (79%) presented ≥ 30%. The mean medication count decreased from 3.9 ± 0.7 (baseline) to 0.7 ± 1.3 (12 months). No intraoperative complications were reported. No adverse events were noted. No secondary filtration surgery was required, although bleb needling was required in one case, 1 month after the surgery.

CONCLUSIONS

PreserFlo with MMC can be used successfully to treat uncontrolled IOP in childhood glaucoma cases with previous failed surgeries. Larger studies with longer follow-up are needed to further explore the role of the device in resistant childhood glaucoma cases.

Novel Surgical Techniques to Control Flow With PreserFlo MicroShunt for Late Hypotony After Baerveldt Drainage Device Implantation

We report a new surgical technique for controlling flow with a PreserFlo MicroShunt, in patients with late postoperative hypotony, following a Baerveldt glaucoma drainage device implantation. We present 2 cases with late postoperative hypotony after Baerveldt-shunt implantations. In both cases, the outflow resistance of the Baerveldt tube was modulated by the insertion of a PreserFlo MicroShunt into the lumen of the Baerveldt tube. In the first case, the Microshunt was inserted through the distal opening of the tube in the anterior chamber. In the second case, an end plate, sided approach was chosen after opening the conjunctiva. In both cases, the hypotony was successfully treated. The intraocular pressure rose immediately after the procedure, and it remained well controlled within the targeted range during the first postoperative months without additional pressure-lowering medication. This novel surgical technique provided predictable flow reductions, according to the Hagen-Poiseuille equation. This approach offers a valuable alternative to permanent tube ligation.

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.

A model for designing intraocular pressure-regulating glaucoma implants

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

A Multi-Lumen Glaucoma Stent With Titratable Pressure-Lowering Effect: A Proof of Concept Study

Purpose

To explore the feasibility of a glaucoma stent with a titratable pressure-lowering effect.

Methods

This was an in vitro study. We created a resin stent with a micro-precision three-dimensional printer. It represented a cylinder with one primary and two secondary lumina. The inner opening of each secondary lumen was sealed with a membrane. We used a surgical eye model to simulate implantation of the stent and a laser procedure analogous to argon laser trabeculoplasty (ALT) to ablate each membrane. To study the fluid dynamics, we used a high-precision syringe pump and measured the steady-state pressure for one, two, and three lumina in parallel at flow rates of 2.5, 5.0, and 10.0 µL/min.

Results

The stent could be implanted into the eye model and visualized in the anterior chamber angle. Coloring the membrane facilitated laser membranotomy, and a 0.1-second laser pulse with 250-mW power was enough to ablate one membrane. The steady-state pressure for one lumen increased linearly with increasing flow rate, in accordance with the Hagen–Poiseuille equation. Two and three lumina in parallel decreased the pressure by factors of 2.1 and 3.2, respectively, in accordance with the electronic–hydraulic analogy and Ohm's law applied to parallel resistors.

Conclusions

The study presents proof of concept for a glaucoma stent with multiple lumina, which can be separately opened with an ALT-like procedure to induce a predictable, stepwise increase in pressure-lowering effect.

Translational Relevance

The glaucoma stent in this experimental study can be reproduced in a biocompatible material and further studied in vivo.

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.

Degeneration of retina-brain components and connections in glaucoma: Disease causation and treatment options for eyesight preservation

Eyesight is the most important of our sensory systems for optimal daily activities and overall survival. Patients who experience visual impairment due to elevated intraocular pressure (IOP) are often those afflicted with primary open-angle glaucoma (POAG) which slowly robs them of their vision unless treatment is administered soon after diagnosis. The hallmark features of POAG and other forms of glaucoma are damaged optic nerve, retinal ganglion cell (RGC) loss and atrophied RGC axons connecting to various brain regions associated with receipt of visual input from the eyes and eventual decoding and perception of images in the visual cortex. Even though increased IOP is the major risk factor for POAG, the disease is caused by many injurious chemicals and events that progress slowly within all components of the eye-brain visual axis. Lowering of IOP mitigates the damage to some extent with existing drugs, surgical and device implantation therapeutic interventions. However, since multifactorial degenerative processes occur during aging and with glaucomatous optic neuropathy, different forms of neuroprotective, nutraceutical and electroceutical regenerative and revitalizing agents and processes are being considered to combat these eye-brain disorders. These aspects form the basis of this short review article.

Corneal Endothelial Cell Loss in Patients After Minimally Invasive Glaucoma Surgery: Current Perspectives

Minimally invasive glaucoma surgery (MIGS) is a rapidly expanding category of surgical glaucoma treatment options that offer a superior safety profile compared with traditional approaches for reducing intraocular pressure. However, MIGS may cause corneal endothelial cell loss; therefore, it has been receiving increasing attention. This systematic review aimed to evaluate and compare the rate and degree of corneal endothelial loss after MIGS. First, this paper presents an overview of the theoretical effectiveness of MIGS, the fundamental aspects regarding the roles of endothelial cells, and the effect of cataract surgery on the quality and count of endothelial cells. Further, we detail the various surgical techniques involved in MIGS, the development of these techniques over the time, and clinical aspects to consider with respect to the endothelial cell count. We discuss in detail the COMPASS-XT study, which was based on data collected over 5 years, reported that withdrawal of the CyPass Micro-Stent (Alcon Laboratories) yielded increased corneal endothelial cell loss. Generally, MIGS procedures are considered safe, with the incidence of complications ranging from 1% to 20% depending on the surgery type; however, there is still need for studies with longer follow-up. Thus, an adequate count of endothelial cells in the central cornea portion is recommended as necessary for candidate patients for MIGS.

Two-Year Outcome of Surgery in Glaucoma Patients

PURPOSE

To evaluate the 2-year surgical treatment outcome in glaucoma patients.

METHODS

A retrospective, single-center, interventional study was performed on 160 eyes of 125 patients suffering glaucoma, including POAG (82 eyes), pseudoexfoliation (PEX) (59 eyes), pigment dispersion (8 eyes), and secondary glaucoma (2 eyes). Eyes with uncontrolled intraocular pressure (IOP) or signs of glaucoma progression despite medical treatment were included to undergo either trabeculectomy (TE), XEN implantation, combined TE with phacoemulsification (TE + IOL), or XEN implantation with phacoemulsification surgery (XEN + IOL). Primary efficacy outcome was the mean IOP reduction. Secondary outcome was the mean reduction in the number of medications. The data were compared at baseline vs.1 day, 1 week, and 1, 3, 6, 12, and 24 months following surgery. For statistical evaluation, ANOVA-based linear mixed-effects models were performed with SPSS.

RESULTS

The mean IOP reduction in a 2-year follow-up was 30.31% (22.17 vs. 15.45 mmHg, p < 0.001). The mean number of antiglaucoma medications was reduced from 2.87 to 0.58 (p = 0.001), where TE alone or combined surgeries seemed to be more effective than isolated XEN surgery. Transient IOP hypotony on the first postoperative day occurred in PEX patients following TE surgery (p = 0.024). At 6 months, PEX patients with isolated XEN surgery showed a transient IOP increase, whereas those after combined TE + IOL surgery showed the lowest IOP within the PEX group compared to other glaucoma patients (p < 0.026).

CONCLUSIONS

After 2 years, all performed glaucoma surgeries achieved a significant reduction in IOP and the number of antiglaucoma medications.

Minimally Invasive Micro Sclerostomy (MIMS) Procedure: A Novel Glaucoma Filtration Procedure

PRCIS

Intermediate-term results suggest that ab interno Minimally Invasive Micro Sclerostomy (MIMS) stent-less subconjunctival filtration procedure is a promising treatment option for patients with open-angle glaucoma (OAG).

PURPOSE

MIMS is a novel ab interno, stent-less, subconjunctival filtration procedure. This study set to investigate the safety, performance, and efficacy of MIMS in OAG patients.

METHODS

Prospective, open-label, single arm clinical trial with intrasubject comparisons. Study participants were adults with OAG who were candidates for a filtration procedure. Patients were operated by a single surgeon (A.A.) in Chennai, India. Following mitomycin-C pretreatment, ab interno MIMS procedure was performed alone or combined with phacoemulsification surgery. Procedure-related complications and adverse events were assessed. Primary outcomes: patients (%) achieving an intraocular pressure (IOP) ≥5 mm Hg and ≤18 mm Hg, and an IOP reduction of >20% as compared with baseline, with or without hypotensive medications, with no need for recurrent surgery.

RESULTS

Twenty-one phacoemulsification-MIMS and 10 standalone MIMS procedures were performed. Mean age was 63.94±6.33 years. Mean duration of MIMS was 1:58±0:25 (min:s). Scleral tunnels were achieved in all cases. No device malfunctions, intraoperative complications, or serious adverse events were reported. Five (16.12%) patients presented with iris clogging 1 to 24 weeks following procedure. Two were treated with laser and 3 required trabeculectomy. Mean IOP change from baseline at 24 weeks was 47.4% (31.2 to 16.4 mm Hg, P<0.0001, n=23). The mean difference was -14.8 mm Hg (95% confidence interval: -17.6, -11.9) with no statistically significant differences between groups. Qualified success was achieved in 21 (84%), 17 (74%), and 13 (93%) after 12, 24, and 52 weeks, respectively. Complete success was achieved in 17 (68%), 13 (57%), and 8 (57%) after 12, 24, and 52 weeks, respectively.

CONCLUSIONS

The interim results suggest that MIMS procedure may be a simple and effective surgical option for early OAG patients requiring target IOP in high teens although iris clogging of incision site is the major concern with this procedure.

The surgical management of glaucoma: A review

After a long period of little change, glaucoma surgery has experienced a dramatic rise in the number of possible procedures in the last two decades. Glaucoma filtering surgeries with mitomycin C and glaucoma drainage devices remain the standard of surgical care. Other newer surgeries, some of which are minimally or microinvasive glaucoma surgeries, target existing trabecular outflow, enhance suprachoroidal outflow, create subconjunctival blebs, or reduce aqueous production. Some require the implantation of a device such as the iStent, Hydrus, Ex-PRESS, XEN and PRESERFLO, whilst others do not-Trabectome, Kahook dual blade, Ab interno canaloplasty, gonioscopy-assisted transluminal trabeculotomy, OMNI and excimer laser trabeculotomy. Others are a less destructive variation of an established procedure, such as micropulse transscleral cyclophotocoagulation, endoscopic cyclophotocoagulation and ultrasound cycloplasty. Cataract surgery alone can be a significant glaucoma operation. These older and newer glaucoma surgeries, their mechanism of action, efficacy and complications are the subject of this review.

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.

Conventional glaucoma implants and the new MIGS devices: a comprehensive review of current options and future directions

Glaucoma is a progressive optic neuropathy that is the second leading cause of preventable blindness worldwide, after cataract formation. A rise in the intraocular pressure (IOP) is considered to be a major risk factor for glaucoma and is associated with an abnormal increase of resistance to aqueous humour outflow from the anterior chamber. Glaucoma drainage devices have been developed to provide an alternative pathway through which aqueous humour can effectively exit the anterior chamber, thereby reducing IOP. These devices include the traditional aqueous shunts with tube-plate design, as well as more recent implants, such as the trabeculectomy-modifying EX-PRESS^® implant and the new minimally invasive glaucoma surgery (MIGS) devices. In this review, we will describe each implant in detail, focusing on their efficacy in reducing IOP and safety profile. Additionally, a critical and evidence-based comparison between these implants will be provided. Finally, we will propose potential developments that may help to improve the performance of current devices.

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.

Therapeutic Drugs and Devices for Tackling Ocular Hypertension and Glaucoma, and Need for Neuroprotection and Cytoprotective Therapies

Damage to the optic nerve and the death of associated retinal ganglion cells (RGCs) by elevated intraocular pressure (IOP), also known as glaucoma, is responsible for visual impairment and blindness in millions of people worldwide. The ocular hypertension (OHT) and the deleterious mechanical forces it exerts at the back of the eye, at the level of the optic nerve head/optic disc and lamina cribosa, is the only modifiable risk factor associated with glaucoma that can be treated. The elevated IOP occurs due to the inability of accumulated aqueous humor (AQH) to egress from the anterior chamber of the eye due to occlusion of the major outflow pathway, the trabecular meshwork (TM) and Schlemm’s canal (SC). Several different classes of pharmaceutical agents, surgical techniques and implantable devices have been developed to lower and control IOP. First-line drugs to promote AQH outflow via the uveoscleral outflow pathway include FP-receptor prostaglandin (PG) agonists (e.g., latanoprost, travoprost and tafluprost) and a novel non-PG EP2-receptor agonist (omidenepag isopropyl, Eybelis^®). TM/SC outflow enhancing drugs are also effective ocular hypotensive agents (e.g., rho kinase inhibitors like ripasudil and netarsudil; and latanoprostene bunod, a conjugate of a nitric oxide donor and latanoprost). One of the most effective anterior chamber AQH microshunt devices is the Preserflo^® microshunt which can lower IOP down to 10–13 mmHg. Other IOP-lowering drugs and devices on the horizon will be also discussed. Additionally, since elevated IOP is only one of many risk factors for development of glaucomatous optic neuropathy, a treatise of the role of inflammatory neurodegeneration of the optic nerve and retinal ganglion cells and appropriate neuroprotective strategies to mitigate this disease will also be reviewed and discussed.

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.

Efficacy and safety data for the Ab interno XEN45 gel stent implant at 3 Years: A retrospective analysis

PURPOSE

To report efficacy and safety measures of the XEN45 gel stent at 36 months in the UK National Health Service setting.

METHODS

Retrospective non-comparative audit of the records of patients who underwent XEN45 implantation between June 2015 and May 2017 was performed. Main outcome measures were intraocular pressure and number of antihypertensive medications used. Failure was defined as need for further surgery or stent removal. Success was defined as a 20% decrease in intraocular pressure without the need for additional glaucoma medications or a reduction in antihypertensive medications without an increase in baseline intraocular pressure. Needling rates and preoperative factors effect were assessed.

RESULTS

The cohort included 205 patients (205 eyes) with primary open angle glaucoma (84.4%), angle closure glaucoma (7.8%), or refractory glaucoma (7.8%), 62.9% had a stand-alone procedure and 37.1%, a combined phaco-XEN45 procedure. Mean intraocular pressure was 22.6 ± 7.0 mmHg at baseline compared to 14.7 ± 3.8 mmHg at 24 months and 14.0 ± 2.9 mmHg at 36 months (p < 0.001 for both). Mean number of medications used was 2.6 ± 1.1 at baseline compared to 0.5 ± 0.9 and 0.6 ± 1.0, at 24- and 36-months, respectively (p < 0.001 for both). The failure rate at 36 months was 25%. Needling was required in 36.6%. Evaluation of background factors yielded an increased failure rate in non-Caucasians compared to Caucasians (74% vs 21%, p < 0.001).

CONCLUSION

XEN45 implantation is effective and safe at 36 months' follow-up. Patients should be advised regarding the risk of failure and possible need for bleb revisions. Careful patient selection may be required.

Surgical and Perioperative Considerations for the Treatment of Cataract in Eyes with Glaucoma: A Literature Review

Cataract surgery in the presence of glaucoma poses certain challenges that need to be addressed to offer the maximum benefit without complications. In this paper, we are reviewing the preoperative assessment, surgical options, the planning, and postoperative care. Cataract surgery can help reduce the intraocular pressure alone or combined with MIGS. When performed in patients with glaucoma, it can transiently increase the intraocular pressure and later on decrease the IOP to levels lower than the postoperative. The preoperative IOP and biometric characteristics are the main predictors of the postoperative course of IOP. The combination of cataract surgery with trabeculectomy remains controversial, in terms of best timing of each operation.

Long-term Efficacy of Mitomycin C Augmented Trabeculectomy in a Mixed Pediatric Glaucoma Cohort

PRECIS

This paper reports a retrospective consecutive case series investigating the efficacy of Mitomycin C-augmented trabeculectomy in the treatment of primary and secondary pediatric glaucoma in a mixed etiology, multiethnic cohort of patients.

PURPOSE

To evaluate the long-term efficacy and safety of Mitomycin C-augmented trabeculectomy in a mixed, tertiary-referral, pediatric glaucoma cohort.

METHODS

Retrospective consecutive review of all children (37 eyes) undergoing Mitomycin C-augmented trabeculectomy by a single surgeon between 2008 and 2016. Seventeen eyes (45.9%) had primary congenital glaucoma, and 20 eyes (54.1%) had secondary glaucoma. The median age at surgery was 11 months (range, 2 to 146). The mean follow-up was 69.2±4.7 months (range, 3.5 to 107.9).

RESULTS

Overall, trabeculectomy was successful in 80.6% of eyes at 12 months, 60.5% at 3 years, and 57.5% at 5 years. 45.9% cases (17 eyes) required further laser or surgery for uncontrolled intraocular pressure (IOP) and were therefore deemed as failures. The time to failure ranged from 0.4 to 65.1 months (mean, 22.2±5.1 mo). The proportion of children achieving visual acuity of 1.0 LogMAR equivalent or better increased from 43.2% preoperatively to 63.6% at 1 year and 68% at 5 years. The mean IOP reduced from 24.85±0.88 mm Hg preoperatively to 15.14±0.94 mm Hg at 3 months (39% reduction) and 17.42±1.08 mm Hg at 5 years (30% reduction). IOP-lowering medication requirement reduced from 4.14±0.20 agents preoperatively to 0.84±0.22 at 3 months (80% reduction) and 1.78±0.36 at 5 years (57% reduction). There were no sight-threatening complications such as hyphaema, bleb leak, chronic hypotony, endophthalmitis, retinal detachment, or loss of light perception.

CONCLUSIONS

This study provides valuable evidence that Mitomycin C-augmented trabeculectomy is safe and effective as a treatment of primary or secondary pediatric glaucoma, with particularly encouraging results in cases of secondary glaucoma. Trabeculectomy offers the potential for delaying or avoiding glaucoma drainage device surgery in a significant proportion of children.

[Results of filtering trabeculotomy (FTO) compared to conventional trabeculectomy (TE)-a matched case control study]

Ziel

Ziel dieser Studie war es, die 2‑Jahres-Ergebnisse der filtrierenden Trabekulotomie (FTO) im Vergleich zur konventionellen Trabekulektomie (TE) bei primärem Offenwinkelglaukom, Pseudoexfoliationsglaukom und Pigmentglaukom zu untersuchen.

Patienten und Methoden

Es wurden 30 konsekutive Patienten nach FTO und 87 Patienten nach TE nach intraokularem Druck (IOD) und Alter im Verhältnis 1:3 gematcht. Primärer Endpunkt war das Erreichen des Zieldrucks nach 2 Jahren. Als vollständiger Erfolg wurde ein IOD ohne Medikamente von ≤ 18 mm Hg bei gleichzeitiger IOD-Reduktion um ≥ 30 % definiert, als qualifizierter Erfolg, wenn hierfür zusätzlich Medikamente erforderlich waren. Sekundäre Endpunkte waren mittlere Drucksenkung, resultierende Sehschärfe, Komplikationen und nachfolgende Operationen. Die Operationstechnik der filtrierenden Trabekulotomie ist als Video zu diesem Beitrag abrufbar.

Ergebnisse

Zwei-Jahres-Daten konnten von 27 Patienten aus der FTO-Gruppe und 68 Patienten aus der TE-Gruppe erhoben werden. Die Patienten beider Gruppen wurden vor Beginn der Studie bezüglich Alter und IOD gematcht, waren aber auch bezüglich Sehschärfe, Geschlecht und Medikation nicht unterschiedlich. Der Median des präoperativen IOD unter Therapie betrug in beiden Gruppen 23,0 mm Hg. Nach den oben genannten Kriterien wurde ein qualifizierter 2‑Jahres-Erfolg bei 70,4 % der FTO-Gruppe und bei 77,6 % der TE-Gruppe erzielt (p = 0,60), ein vollständiger 2‑Jahres-Erfolg bei 33,3 % der FTO-Gruppe und bei 56,7 % der TE-Gruppe (p = 0,07). Beide Operationsmethoden senkten den Augeninnendruck nach 24 Monaten signifikant (p < 0,001), und zwar auf 12,8 mm Hg in der FTO-Gruppe und 11,0 mm Hg in der TE-Gruppe. Die Sehschärfe war postoperativ bei beiden Gruppen etwas verringert, unterschied sich jedoch nicht signifikant zwischen beiden Gruppen. Komplikations- und Reoperationsrate waren gering und unterschieden sich nicht zwischen den Gruppen.

Schlussfolgerung

FTO und TE sind nach 2 Jahren weitgehend gleichwertig bezüglich Zieldruck, IOD-Senkung, Sehschärfe und Komplikationen.

Video online

Die Online-Version dieses Beitrags (10.1007/s00347-021-01365-w) enthält ein Video zur Operationstechnik der filtrierenden Trabekulotomie. Beitrag und Video stehen Ihnen auf www.springermedizin.de zur Verfügung. Bitte geben Sie dort den Beitragstitel in die Suche ein, das Zusatzmaterial finden Sie beim Beitrag unter „Ergänzende Inhalte“.

Microinvasive Glaucoma Surgery: A Review of Schlemm's Canal-Based Procedures

Microinvasive glaucoma surgery has gained popularity over the past decade. It can be performed using three different mechanisms. In the present review, we focused on Schlemm’s canal (SC)-based surgery, which increases aqueous humor (AH) outflow into the aqueous veins by either removal of the trabecular meshwork (TM) or an increase in the tension in the TM. In primary open-angle glaucoma (POAG), the TM is the most likely region for increased AH outflow resistance. Theoretically, removal of the TM can improve the AH outflow; hence, glaucoma specialists focus on microsurgical dissection of the TM. In this review, we analyzed the available literature to examine SC-related microsurgical modalities based on the histopathological proofs of the localization of resistance of the AH outflow. First, we considered the role, anatomy, and physiology of the TM and SC. We referred to studies that describe the mechanisms and potential pathways, related to increased intraocular pressure in the POAG, that are targeted using the SC-related microsurgical interventions. Next, we took a closer look at the gonioscopic tools necessary for an ab-interno approach and explored incision canal surgery: ab-interno trabeculectomy using different instrumentation (Trabectome^®, Kahook Dual Blade) and variations of the technique. Thereafter, we discussed ab-interno canaloplasty, explaining the technique and reviewing its effectiveness. Finally, we presented the scope for future research in the field. Although the iStent also targets SC by bypassing it, this device has been reviewed extensively elsewhere.

History, presence, and future of mitomycin C in glaucoma filtration surgery

PURPOSE OF REVIEW

Mitomycin C (MMC) is an alkylating agent with extraordinary ability to crosslink DNA, preventing DNA synthesis. By this virtue, MMC is an important antitumor drug. In addition, MMC has become the gold standard medication for glaucoma filtration surgery (GFS). This eye surgery creates a passage for drainage of aqueous humor (AqH) out of the eye into the sub-Tenon's space with the aim of lowering the intraocular pressure. A major cause of failure of this operation is fibrosis and scarring in the sub-Tenon's space, which will restrict AqH outflow. Intraoperative application of MMC during GFS has increased GFS success rate, presumably mainly by reducing fibrosis after GFS. However, still 10% of glaucoma surgeries fail within the first year.

RECENT FINDINGS

In this review, we evaluate risks and benefits of MMC as an adjuvant for GFS. In addition, we discuss possible improvements of its use by adjusting dose and method of administration.

SUMMARY

One way of improving GFS outcome is to prolong MMC delivery by using a drug delivery system.

Exploiting biomaterial approaches to manufacture an artificial trabecular meshwork: A progress report

Glaucoma is the second leading cause of irreversible blindness worldwide. Glaucoma is a progressive optic neuropathy in which permanent loss of peripheral vision results from neurodegeneration in the optic nerve head. The trabecular meshwork is responsible for regulating intraocular pressure, which to date, is the only modifiable risk factor associated with the development of glaucoma. Lowering intraocular pressure reduces glaucoma progression and current surgical approaches for glaucoma attempt to reduce outflow resistance through the trabecular meshwork. Many surgical approaches use minimally invasive glaucoma surgeries (MIGS) to control glaucoma. In this progress report, biomaterials currently employed to treat glaucoma, such as MIGS, and the issues associated with them are described. The report also discusses innovative biofabrication approaches that aim to revolutionise glaucoma treatment through tissue engineering and regenerative medicine (TERM). At present, there are very few applications targeted towards TM engineering in vivo, with a great proportion of these biomaterial structures being developed for in vitro model use. This is a consequence of the many anatomical and physiological attributes that must be considered when designing a TERM device for microscopic tissues, such as the trabecular meshwork. Ongoing advancements in TERM research from multi-disciplinary teams should lead to the development of a state-of-the-art device to restore trabecular meshwork function and provide a bio-engineering solution to improve patient outcomes.

Discovery to Launch of Anti-allergy (Emadine; Patanol/Pataday/Pazeo) and Anti-glaucoma (Travatan; Simbrinza) Ocular Drugs, and Generation of Novel Pharmacological Tools Such as AL-8810

The eye and eyesight are exquistly designed and are precious, and yet we often take them for granted. Good vision is critical for our long-term survival and for humanity's enduring progress. Unfortunately, since ocular diseases do not culminate in life-and-death scenarios, awareness of the plight of millions of people suffering from such eye ailments is not publicized as other diseases. However, losing eyesight or falling victim to visual impairment is a frightening outlook for most people. Glaucoma, a collection of chronic optic neuropathies, of which the most prevalent form, primary open-angle glaucoma (POAG), is the second leading cause of irreversible blindness. POAG currently afflicts >70 million people worldwide and is an insidious, progressive, silent thief of sight that is asymptomatic. On the other hand, allergic conjunctivitis (AC), and the associated rhinitis ("hay-fever"), frequently victimizes a huge number of people worldwide, especially during seasonal changes. While not life-threatening, sufferers of AC soon learn the value of drugs to treat their signs and symptoms of AC as they desire rapid relief to overcome the ocular itching/pain, redness, and tearing AC causes. Herein, I will describe the collective efforts of many researchers whose industrious, diligent, and dedicated team work resulted in the discovery, biochemical/pharmacological characterization, development and eventual launch of drugs to treat AC (e.g., olopatadine [Patanol/Pataday/Pazeo] and emedastine [Emedine]), and for treating ocular hypertension and POAG (e.g., travoprost [Travatan ] and Simbrinza). This represents a personal perspective.

A Case of Delayed-onset Hemorrhagic Choroidal Detachment After PreserFlo Microshunt Implantation in a Glaucoma Patient Under Anticoagulant Therapy

PURPOSE

To describe a case of delayed-onset hemorrhagic choroidal detachment (HCD) in a patient affected by primary open-angle glaucoma (POAG) undergone PreserFlo Microshunt implantation.

CASE REPORT DESCRIPTION

A 76-year-old patient with POAG, under treatment with Dabigatran (a novel oral anticoagulant), underwent an uncomplicated PreserFlo Microshunt implantation in the left eye. In the first postoperative day, intraocular pressure (IOP) was 6 mm Hg, conjunctival bleb was diffuse, anterior chamber (AC) deep, and device correctly positioned. Twelve days after surgery, the patient had emergency access complaining severe ocular pain and sudden vision loss. Ophthalmological evaluation revealed shallow AC and an IOP of 50 mm Hg. The fundus examination revealed almost kissing HCD.

OUTCOME

Immediate topical treatment with atropine, aqueous humor suppressants, and corticosteroids was started. Because of high IOP, ocular pain, and the presence of almost kissing HCD, surgical drainage of suprachoroidal hemorrhage and removal of PreserFlo Microshunt were performed. An improvement of the clinical condition was observed in the following postoperative days, with partial resolution of the HCD and a decrease of the IOP. On the third postoperative day, there was a worsening of the HCD, with a reduction of the AC depth and IOP elevation. HCD was drained through the previously performed sclerotomies, associated with pars-plana vitrectomy and silicone-oil tamponade. HCD completely resolved during the following 6 weeks, with IOP reduction and partial improvement of visual acuity.

CONCLUSION

Great attention must be taken in patients with glaucoma under treatment with a novel oral anticoagulant, also when planning PreserFlo Microshunt implantation.