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

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

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

The Evolution and Current Landscape of Minimally Invasive Glaucoma Surgeries: A Review

This review examines the evolution, current status, and future potential of minimally invasive glaucoma surgeries (MIGS), a significant advancement in the treatment of glaucoma, a leading cause of irreversible blindness. MIGS offer a less invasive alternative to traditional glaucoma surgeries, primarily aimed at reducing intraocular pressure, minimizing tissue trauma, and providing a safer profile. With the emergence of devices such as the Trabectome, iStent, and others, MIGS have expanded the surgical toolkit, allowing personalized, patient-centered care. Despite their advantages, MIGS face challenges such as efficacy in severe cases, long-term data, and accessibility. Ongoing research and technological innovations continue to refine their capabilities and applications, promising to further transform glaucoma management and patient outcomes. This paper provides an in-depth analysis of MIGS, reflecting on their impact and contemplating future directions in this dynamically evolving field.

Therapeutic strategies for glaucoma and optic neuropathies

Glaucoma is a neurodegenerative eye disease that causes permanent vision impairment. The main pathological characteristics of glaucoma are retinal ganglion cell (RGC) loss and optic nerve degeneration. Glaucoma can be caused by elevated intraocular pressure (IOP), although some cases are congenital or occur in patients with normal IOP. Current glaucoma treatments rely on medicine and surgery to lower IOP, which only delays disease progression. First-line glaucoma medicines are supported by pharmacotherapy advancements such as Rho kinase inhibitors and innovative drug delivery systems. Glaucoma surgery has shifted to safer minimally invasive (or microinvasive) glaucoma surgery, but further trials are needed to validate long-term efficacy. Further, growing evidence shows that adeno-associated virus gene transduction and stem cell-based RGC replacement therapy hold potential to treat optic nerve fiber degeneration and glaucoma. However, better understanding of the regulatory mechanisms of RGC development is needed to provide insight into RGC differentiation from stem cells and help choose target genes for viral therapy. In this review, we overview current progress in RGC development research, optic nerve fiber regeneration, and human stem cell-derived RGC differentiation and transplantation. We also provide an outlook on perspectives and challenges in the field.

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.

Posterior corneoscleral limbus: Architecture, stem cells, and clinical implications

The limbus is a transition from the cornea to conjunctiva and sclera. In human eyes, this thin strip has a rich variation of tissue structures and composition, typifying a change from scleral irregularity and opacity to corneal regularity and transparency; a variation from richly vascularized conjunctiva and sclera to avascular cornea; the neural passage and drainage of aqueous humor. The limbal stroma is enriched with circular fibres running parallel to the corneal circumference, giving its unique role in absorbing small pressure changes to maintain corneal curvature and refractivity. It contains specific niches housing different types of stem cells for the corneal epithelium, stromal keratocytes, corneal endothelium, and trabecular meshwork. This truly reflects the important roles of the limbus in ocular physiology, and the limbal functionality is crucial for corneal health and the entire visual system. Since the anterior limbus containing epithelial structures and limbal epithelial stem cells has been extensively reviewed, this article is focused on the posterior limbus. We have discussed the structural organization and cellular components of the region beneath the limbal epithelium, the characteristics of stem cell types: namely corneal stromal stem cells, endothelial progenitors and trabecular meshwork stem cells, and recent advances leading to the emergence of potential cell therapy options to replenish their respective mature cell types and to correct defects causing corneal abnormalities. We have reviewed different clinical disorders associated with defects of the posterior limbus and summarized the available preclinical and clinical evidence about the developing topic of cell-based therapy for corneal disorders.

Can We Ever Win with a Suprachoroidal Implant?

How to cite this article: Au L, Bhartiya S. Can We Ever Win with a Suprachoroidal Implant? J Curr Glaucoma Pract 2023;17(2):55-57.

Comparison of Safety and Efficacy of Hydrus and iStent Combined with Phacoemulsyfication in Open Angle Glaucoma Patients: 24-Month Follow-Up

The paper presents the results of a 24-month-long observation comparing the effectiveness and safety of two micro-invasive glaucoma surgery (MIGS) devices: Hydrus Microstent and iStent Trabecular Bypass in combination with cataract phacoemulsification in the treatment of open-angle glaucoma. We also analyzed the impact of preoperative factors on achieving surgical success in both surgical methods. The prospective, comparative, non-randomized study included 65 glaucoma surgeries. In 35 patients (53.8%), an iStent implant procedure was performed, while 30 patients (46.2%) underwent a Hydrus implant procedure. The demographic data was similar in both treatment groups. At 24 months after surgery, the mean IOP in the iStent group was 15.9 ± 3.0 mmHg and in the Hydrus group 16.2 ± 1.8 mmHg. The difference between the mean iStent vs Hydrus after two years of treatment was -0.3 (p = 0.683). At the 24 month follow-up, the average change in the number of antiglaucoma medications used was 71.7% in the iStent group and 79.6% in the Hydrus group. The difference in mean percentage change between groups was 7.9% in favor of Hydrus. Patients under the age of 70 may benefit from a greater risk reduction in the Hydrus group (HR = 0.81), while those over the age of 70 may benefit from a risk reduction in the iStent group (HR = 1.33). IOP cases with >18 mmHg before the surgery have a better chance of surgical success with the Hydrus method (HR = 0.28), and with IOP < 18 mmHg in the iStent group (HR = 1.93). Cases with more drugs (≥3 drugs) are more favorable in the Hydrus group (HR = 0.23), while those with a maximum of two drugs have a better prognosis in the iStent group (HR = 2.23). The most common postoperative complication was the presence of erythrocytes in the anterior chamber (AC), found in 40.0% of operated eyes in the Hydrus group. The profile of observed complications and significant improvement in visual acuity allows us to consider both implants as a safe way of treating patients with early or moderate glaucoma and co-existing cataracts.

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 ab Externo Phaco-Canaloplasty versus First-Generation iStent Bypass Implantation Combined with Phacoemulsification in Patients with Primary Open Angle Glaucoma-Early Results

This study evaluated the early outcomes of the hypotensive efficacy and safety profile of ab externo phaco-canaloplasty versus first-generation iStent bypass implantation combined with phacoemulsification in patients with primary open-angle glaucoma (POAG). In total, 82 patients with POAG comprising 92 eyes were divided into phaco-canaloplasty (Group PC, (n = 47) or iStent combined with phacoemulsification (Group PiS, n = 45) groups. Primary outcome measures were intraocular pressure (IOP) reduction and number of glaucoma medications. Secondary outcome measures were best-corrected visual acuity (BCVA), endothelial cell density (EECD), changes in anterior chamber depth (ACD), and complication rate. The follow-up period was approximately 6 months. Preoperative IOPs were 17.30 (15.00; 19.85) mmHg and 17.50 (15.10; 20.90) mmHg in the PC and PiS groups, respectively (p = 0.876). At the end of the follow-up, IOP decreased to 15.00 (13.00; 16.00) mmHg and 15.00 (14.00; 17.00) mmHg in the PC and PiS groups, respectively (p = 0.438). Medication usage decreased from 2.08 to 0.12 and 1.40 to 0.04 in PC and PiS eyes, respectively. Most patients in both groups were medication-free at 6 months follow-up. After 6 months of observation, EECD in PC and PiS groups decreased from 2309.50 (2032.00; 2533.00) to 1966.50 (1262.00; 2353.50) and 2160.00 (1958.50; 2372.50), to1231.00 (1089.00; 2050.00), respectively (p = 0.037). Pre-surgery BCVA was 0.80 (0.50; 1.00) and 0.60 (0.40; 1.00) in PC and PiS eyes, respectively (p = 0.456). Follow-up BCVA was 0.95 (0.60; 1.00) for PC and 1.00 (1.00; 1.00) for PiS. Hyphema and corneal oedema were noted on the first day post-surgery in both groups. Subsequent complications included a transient increase in IOP in the PC group. Phaco-canaloplasty and iStent bypass implantation combined with phacoemulsification significantly lowered IOP and decreased medication burden. All eyes in both groups maintained or exhibited improved BCVA relative to baseline. Both surgeries had low postoperative complication rates and exhibited comparable safety profiles over 6-month follow-up in patients with POAG.

Comparison of Efficacy of Combined Phacoemulsification and iStent Inject versus Combined Phacoemulsification and Hydrus Microstent

Aim

This study aims to compare the efficacy and safety of combined phacoemulsification with iStent inject (Phaco-iStent) and Hydrus microstent (Phaco-Hydrus).

Methods

This was a retrospective comparative study of patients who underwent Phaco-iStent from April 2019 to August 2020 and Phaco-Hydrus from August 2019 to December 2020 at a tertiary eye centre in Singapore. Sixty-nine Phaco-iStent eyes and 49 Phaco-Hydrus eyes were included in this study. Complete surgical success was defined as freedom from second glaucoma surgery, Intraocular pressure (IOP) of 18 mmHg or less, and discontinuation of all antiglaucoma medications.

Results

At 12 months, both Phaco-iStent and Phaco-Hydrus groups had comparable surgical success rate (68.1% vs 51%, p=0.061), reduction in antiglaucoma medication use (-1.3 ± 0.1 vs -1.4 ± 0.10, p=0.880) and intraocular pressure reduction (-1.1 ± 0.5 mmHg vs -1.6 ± 0.9 mmHg, p=0.323). Overall intraoperative and postoperative complications rate were similar in both groups, though hyphema was more commonly seen in early postoperative period in the Phaco-Hydrus compared to the Phaco-iStent group (8% vs 0%, p=0.028), with majority of cases resolving without any need for surgical intervention. Device obstruction was also more common in the Phaco-Hydrus group compared to the Phaco-iStent group (14% vs 4.3%, p=0.04).

Conclusion

Phaco-iStent and Phaco-Hydrus have similar surgical efficacy and safety profiles at 12 months.

Impact of minimally invasive glaucoma surgery on the ocular surface and quality of life in patients with glaucoma

Background:

Minimally invasive glaucoma procedures are emerging as clinically effective and safe glaucoma management approaches; however, evidence regarding quality-of-life outcomes is limited.

Objectives:

To explore the impact of minimally invasive glaucoma surgery (MIGS) combined with phacoemulsification on patient-reported outcomes and clinical parameters related to ocular surface disease in people with glaucoma.

Design:

Retrospective observational study.

Methods:

Fifty-seven consecutive patients were examined prior to undergoing iStent combined with phacoemulsification with or without adjunctive endocyclophotocoagulation and at 4-month follow-up.

Results:

At follow-up, on average patients returned statistically significantly improved scores on glaucoma-specific (GQL-15, p < 0.001; GSS, p < 0.001), general health (EQ-5D, p = 0.02) and ocular surface PROMs (OSDI, p = 0.001). Patients were using fewer eye drops on average after MIGS compared with before surgery (1.1 ± 0.9 versus 1.8 ± 0.8; p < 0.001). Undergoing MIGS was associated with improved tear film break-up time ( p < 0.001) and reduced corneal fluorescein staining ( p < 0.001).

Conclusion:

This retrospective audit shows quality of life and clinical parameters related to the ocular surface are improved following MIGS combined with phacoemulsification in patients previously treated with anti-glaucoma therapy.

Early Complications and Results of Preserflo MicroShunt in the Management of Uncontrolled Open-Angle Glaucoma: A Case Series

We analyze the surgical outcomes and early complications with their management of the Preserflo MicroShunt (Santen Pharmaceutical Co., Ltd., Osaka, Japan) at six-month follow-up. The study is conducted between March 2021 and May 2022. Best-corrected visual acuity (BCVA) logMAR, intraocular pressure (IOP), and changes in glaucoma medications are assessed. Thirty eyes of 30 patients (22 women [73.3%] and 8 men [26.7%]) are included. They are augmented with mitomycin C (MMC) 0.5 mg/mL (8 subjects) or MMC 0.2 mg/mL (22 subjects) intraoperatively. BCVA is significantly higher one day after the treatment than before the treatment (MD with 95% CI = 0.05 (<0.01; 0.30); p = 0.045) when analyzing all patients. Such dependency is not observed when analyzing only patients treated with MMC 0.2 or 0.5 mg/mL (p > 0.050 for both analyses). No other statistically significant differences are detected in the level of BCVA before and after treatment. Among the patients, overall IOP is significantly lower at each time point after treatment than before surgery (p < 0.001 for all analyses). Among patients augmented with MMC 0.2 mg/mL, the IOP level is also significantly lower at each time point after treatment than before treatment (p ≤ 0.001 for all analyses). The same differences are observed among patients with MMC = 0.5—the IOP level is significantly lower at each time point after treatment than before treatment (p < 0.050 for all analyses). Five subjects (16.7%) require anti-glaucoma medications three months after the procedure. Early complications (hypotony, choroidal effusion, keratitis, hyphema, and bleb fibrosis) are observed in 46.7% of cases. Our early results show that Preserflo MicroShunt is safe and effective for lowering IOP; however, it is not free from transient complications.

iStent inject Trabecular Micro-Bypass with or Without Cataract Surgery Yields Sustained 5-Year Glaucoma Control

Introduction

This study evaluated the 5-year effectiveness and safety of iStent inject^® trabecular micro-bypass with or without cataract surgery (Combined or Standalone, respectively) in patients with open-angle glaucoma (OAG).

Methods

This prospective longitudinal case series included consecutive iStent inject cases from a single surgeon at a large German academic hospital. Intraocular pressure (IOP), medications, safety, and indicators of disease stability through 5 years were assessed in the Overall cohort and in subgroup analyses stratified by usage (Combined or Standalone).

Results

Preoperative mean IOP in the Overall cohort (n = 125) was 23.5 ± 6.2 mmHg on 2.68 ± 1.02 mean medications, reducing to 14.1 ± 1.8 mmHg on 0.77 ± 0.82 medications at 5 years (40% and 71% reductions, respectively; both p < 0.001). All but 1 eye (> 99%) were on medication(s) preoperatively, but 46% were medication-free at 5 years (p < 0.001). In Combined eyes (n = 81), mean IOP decreased by 39% (22.6 mmHg to 13.8 mmHg, p < 0.001) and medications by 69% (2.52 to 0.78, p < 0.001). In Standalone eyes, mean IOP reduced by 42% (25.3 mmHg to 14.6 mmHg, p < 0.001) and medications by 75% (2.98 to 0.74, p < 0.001). At final follow-up, 83% of eyes had achieved ≥ 20% IOP reduction, and all but 1 eye (> 99%) had the same or lower IOP versus preoperative; all eyes (100%) maintained or reduced their medication burden versus preoperative. Favorable safety included 0 intraoperative complications and 0 filtration surgeries through 5 years. Long-term indicators of disease stability (visual fields, retinal nerve-fiber layer thickness, and cup:disc ratio) were unchanged over the course of 5-year follow-up.

Conclusions

iStent inject produced significant and durable 5-year reductions in IOP (nearly 10-mmHg reduction) and medications (nearly 2-medication reduction), with stable disease parameters over time. Combined and Standalone subgroups had similar outcomes.

Long-term outcomes of two first-generation trabecular micro-bypass stents (iStent) with phacoemulsification in primary open-angle glaucoma: eight-year results

Background

The short- and medium-term outcomes of iStent have been extensively studied; however, only few studies have investigated its long-term outcomes. Here, we assessed the long-term efficacy and safety of two iStents with concomitant cataract surgery in glaucomatous eyes while also evaluating measures of disease stability using visual field and optical coherence tomography (OCT) of the optic nerve and the macula throughout 8 years of follow-up.

Methods

This longitudinal, single-center consecutive case series included glaucomatous eyes that underwent implantation of two first-generation trabecular micro-bypass stents (iStent) with concomitant cataract surgery. Eight-year efficacy outcomes included mean intraocular pressure (IOP) and medications, as well as surgical success. Eight-year safety outcomes included best-corrected visual acuity (BCVA), visual field mean deviation (VF-MD), cup-to-disc ratio (CDR), retinal nerve fiber layer (RNFL) thickness, ganglion cell-inner plexiform layer (GC-IPL) thickness, and adverse events.

Results

A total of 62 eyes with primary open-angle glaucoma (POAG) were included. At 8 years postoperative, IOP reduced by 26% from 19.2 ± 3.9 mmHg preoperatively to 14.2 ± 2.4 mmHg (P < 0.001), 91.1% of eyes achieved IOP ≤ 18 mmHg (vs. 51.6% preoperatively), 69.6% of eyes achieved IOP ≤ 15 mmHg (vs. 14.5% preoperatively), and 25% of eyes achieved IOP ≤ 12 mmHg (vs. 1.6% preoperatively). Medication use decreased by 17.9% from 2.8 ± 1.1 preoperatively to 2.3 ± 1.2 (P = 0.018). Surgical success was 90%, as six eyes underwent subsequent glaucoma surgeries. Safety measures of BCVA, CDR, RNFL thickness and GC-IPL thickness remained stable through 8 years postoperative. VF-MD remained stable until postoperative year 5 and subsequently progressed according to the natural history of glaucomatous disease.

Conclusions

Implantation of two iStents with concomitant cataract surgery is an effective and safe treatment option for surgery-naïve POAG eyes, evidenced by significant IOP and medication reductions, reasonable surgical success, and favorable safety outcomes, throughout the 8-year follow-up. Our data additionally supports the efficacy of this combined procedure in stabilizing or slowing disease progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40662-021-00263-1.

Evaluation of the Effect of the First Generation iStent on Corneal Endothelial Cell Loss-A Match Case-Control Study

Glaucoma is the leading cause of irreversible blindness worldwide. The only proven factor in slowing the progression of glaucomatous neuropathy is lower intraocular pressure (IOP), which can be achieved with pharmacology, laser therapy, or surgery. However, these treatments are associated with various adverse effects, including corneal endothelial cell loss (CECL). In recent years, several novel surgeries for reducing the IOP, collectively referred to as minimally invasive glaucoma surgery (MIGS), have been developed, one of which is the iStent. However, the long-term effects of such surgeries remain unknown. We compared a group of patients with open-angle glaucoma and cataract who underwent phacoemulsification alone with a group of patients with similar demographic and clinical characteristics who underwent simultaneous phacoemulsification and iStent implantation. Overall, 26 eyes of 22 subjects who underwent a combined phacoemulsification-iStent procedure and 26 eyes of 24 subjects who underwent cataract surgery were included. Before surgery, endothelial cells accounted to 2228.65 ± 474.99 in iStent group and 2253.96 ± 404.76 in the control group (p = 0.836). After surgery, their number declined to 1389.77 ± 433.26 and 1475.31 ± 556.45, respectively (p = 0.509). There was no statistically significant difference in CECL between the two groups 18–24 months after surgery, despite increased manipulation in the anterior chamber and the presence of an implant in the trabecular meshwork in those with an iStent implant. Thus, iStent bypass implantation is a safe treatment in terms of CECL for mild-to-moderate open-angle glaucoma.