iStent inject: comprehensive review

Imaging of aqueous outflow in health and glaucoma. Justifying the re-direction of aqueous

A wave of less invasive surgical options that target or bypass the conventional aqueous outflow system has been incorporated into routine clinical practice to mitigate surgical risks associated with traditional glaucoma drainage surgery. A blanket surgical approach for open-angle glaucoma is unlikely to achieve the desired IOP reduction in an efficient or economical way. Developing a precise approach to selecting the most appropriate surgical tool for each patient is dependent upon understanding the complexities of the aqueous outflow system and how devices influence aqueous drainage. However, homoeostatic control of aqueous outflow in health and glaucoma remains poorly understood. Emerging imaging techniques have provided an opportunity to study aqueous outflow responses non-invasively in clinic settings. Haemoglobin Video Imaging (HVI) studies have demonstrated different patterns of aqueous outflow within the episcleral venous system in normal and glaucomatous eyes, as well as perioperatively after trabecular bypass surgery. Explanations for aqueous outflow patterns remain speculative until direct correlation with findings from Schlemm's canal and the trabecular meshwork are possible. The redirection of aqueous via targeted stent placement may only be justifiable once the role of the aqueous outflow system in IOP homoeostasis has been defined.

Rates of visual field change and functional progression in glaucoma following trabecular microbypass implantation of iStent technologies: a meta-analysis

BACKGROUND/AIM

While intraocular pressure (IOP) remains the only modifiable risk factor for glaucoma progression, the ultimate goal of glaucoma management is to preserve patients' functional vision and quality of life. To this end, minimally invasive glaucoma surgeries (MIGSs) aim to reduce IOP with minimal eye trauma. Commonly used MIGS devices include iStent technologies, which have well-documented IOP-reducing potential and favourable safety profiles. However, no study concluded on their effect on the rates of visual field (VF) changes. The aim of this meta-analysis is to determine the long-term effect of iStent technology implantation on glaucoma functional progression.

METHODS

Electronic medical literature databases were searched to identify studies reporting on iStent technologies. Reports with follow-up durations <12 months, retention rates <75% and missing VF data were excluded. Fifteen studies reporting on 1115 eyes were identified. The overall weighted mean VF mean deviation (MD) progression, IOP reduction and follow-up duration were calculated.

RESULTS

Weighted mean IOP at baseline was 19.0±3.1 mm Hg. At the end of a 37.9-month mean follow-up (range 12-96 months), a weighted mean 26.6% IOP reduction was achieved (range 15.2%-42.3%). Over the same duration, the weighted mean VF MD progression rate was -0.02±0.34 dBs/year, from a mean baseline of -5.76±5.68 dBs.

CONCLUSION

In this review, which examines functional stability of 1115 eyes, iStent technologies achieved a mean rate of progression of -0.024 dBs/year with serial standard automated perimetry, which is similar to that reported in non-glaucomatous eyes and slower than that reported in medically treated glaucoma.

Fellow-Eye Comparison between Phaco-Tanito Microhook Trabeculotomy and Phaco-iStent Inject W

This study aims to compare the surgical efficacy and safety of the Tanito microhook trabeculotomy (TMH-CE) and iStent inject W (Inject-CE) when performed in combination with cataract surgery on the eyes of glaucoma patients. A total of 78 glaucomatous eyes from 39 participants were retrospectively analyzed. Intraocular pressure (IOP), the number of antiglaucoma medications, best-corrected visual acuity (BCVA), anterior chamber flare (ACF), and corneal endothelial cell density (CECD) were all evaluated preoperatively and at multiple postoperative time points. The preoperative IOP was significantly higher in the TMH-CE (19.6 ± 6.7 mmHg) than in the Inject-CE (15.7 ± 3.8 mmHg) (p < 0.0001). At the 12-month follow-up, reductions in IOP and the number of medications were more pronounced in the TMH-CE (6.6 mmHg, 27.6% and -1.1, respectively) group than Inject-CE (2.7 mmHg, 12.4% and -0.7, respectively) (p < 0.0001 and p = 0.0034), while the IOP and medication-number levels were identical between TMH-CE (13.0 ± 3.3 mmHg and 1.3 ± 0.9, respectively) and Inject-CE (12.9 ± 2.6 mmHg and 1.9 ± 0.9, respectively) (p = 0.88 and p > 0.99, respectively). The TMH-CE group exhibited a higher ACF, a higher frequency of layered hyphema, and a greater anterior chamber floating red blood cells score in the early postoperative periods. Despite these differences, the changes in BCVA, ACF, and CECD were equivalent between the two groups in later follow-up periods. TMH-CE provides a more significant IOP reduction and medication-number reduction compared to Inject-CE, while Inject-CE shows quicker BCVA recovery. This study provides valuable insights for ophthalmologists choosing the most suitable surgical approach for glaucoma and cataract patients.

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: A Review of the Literature

Minimally invasive glaucoma surgery (MIGS) has emerged as a novel approach in the glaucoma treatment spectrum, offering a range of diverse procedures and devices aimed at reducing intraocular pressure (IOP). MIGS can be broadly classified into several categories: those that enhance trabecular outflow (Trabectome, iStent, Hydrus Microstent, Kahook Dual Blade, high frequency deep sclerotomy, and gonioscopy-assisted transluminal trabeculotomy), those that augment suprachoroidal outflow (CyPass Microstent and iStent Supra), those that target Schlemm's canal (TRAB360 and the OMNI Surgical System, Streamline, and Ab Interno Canaloplasty), and conjunctival bleb-forming procedures (EX-PRESS Glaucoma Filtration Device, Xen Gel Stent and PreserFlo MicroShunt). MIGS is considered to have a shorter surgical time and fewer severe complications when compared to traditional glaucoma surgeries such as trabeculectomy and glaucoma drainage device implantation (Ahmed, Baerveldt, and Molteno valves). This literature review comprehensively examines the distinct MIGS devices and procedures, their underlying mechanisms, and clinical outcomes, emphasizing the importance of evaluating the efficacy and complications of each approach individually. As the field of MIGS continues to evolve, it is crucial to prioritize high-quality, long-term studies to better understand the safety and effectiveness of these innovative interventions in glaucoma management.

Position of the ISTENT Inject® Trabecular Micro-Bypass System Visualized with the NIDEK GS-1 Gonioscope-A Postoperative Analysis

Glaucoma is one of the leading causes of irreversible blindness globally and is characterized by the gradual loss of retinal ganglion cells. The primary risk factor for the development and progression of glaucoma is increased intraocular pressure (IOP). Numerous surgical interventions exist to lower IOP should conservative therapy fail. One trend in recent years has been minimally invasive glaucoma surgery (MIGS) as an alternative to traditional methods. The ISTENT inject® is an ab interno trabecular micro-bypass implant designed to be implanted through the trabecular meshwork into the Schlemm's canal to lower IOP. The aim of the study was the postoperative visualization and description of the positioning of the ISTENT inject® using automated circumferential goniophotography. Patients with symptomatic cataracts and mild to moderate primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma (PEX), and pigment-dispersion glaucoma were included who underwent combined cataract surgery with the ISTENT inject® and received postoperative automated gonioscopy with the NIDEK Gonioscope GS-1 to visualize the location of the implant. Twenty-four implants of 14 eyes in 11 patients could be visualized. Out of the implants, 14.3% were in the trabecular meshwork, 46.4% were at the border between the trabecular meshwork and scleral spur, 25% were below the trabecular meshwork, and 14.3% of the implants were not detectable in the gonioscopy. In the overall cohort, a statistically significant IOP reduction was found over the 12-month postoperative observation period. Even in three eyes, in each of which both stents were located below the trabecular meshwork, an IOP reduction over 12 months was observed compared to the baseline IOP. In this study, vertical two-dimensional positioning of the ISTENT inject® was performed for the first time using NIDKE GS-1 automated 360° goniophotography. The method is suitable for postoperative visualization, control, and documentation of positioning after ISTENT inject® implantation. Further studies are needed to analyze the correlation between positioning of the ISTENT inject® in the chamber angle and postoperative IOP reduction.

Spotlight on Schlemm's Canal MicroStent Injection in Patients with Glaucoma

Minimally invasive glaucoma surgery (MIGS) has revolutionized glaucoma care with its favorable safety profile and ability to delay or minimize the need for traditional, bleb-based procedures. Microstent device implantation is a type of angle-based MIGS, which reduces intraocular pressure (IOP) through bypass of the juxtacanalicular trabecular meshwork (TM) and facilitation of aqueous outflow into the Schlemm's canal. Although there are limited microstent devices on the market, multiple studies have evaluated the safety and efficacy of iStent^® (Glaukos Corp.), iStent Inject^® (Glaukos Corp.), and Hydrus^® Microstent (Alcon) in the treatment of mild-to-moderate open-angle glaucoma, with and without concurrent phacoemulsification. This review attempts to provide a comprehensive evaluation of injectable angle-based microstent MIGS devices in the treatment of glaucoma.

Ophthalmic surgery in New Zealand: analysis of 410,099 surgical procedures and nationwide surgical intervention rates from 2009 to 2018

BACKGROUND

Surgical intervention rates (SIR) provide a proxy measure of disease burden, surgical capacity, and the relative risk-benefit ratio of surgery. The current study assessed decade trends in ophthalmic surgery and calculated SIRs for all major classes of commonly performed ophthalmic procedures in New Zealand.

METHODS

Retrospective population-based analysis of all ophthalmic surgical procedures performed in New Zealand from 2009 to 2018. National and regional datasets from public and private health sectors and industry were analysed. SIRs were calculated for all major ophthalmic procedures, and subgrouped by patient demographics.

RESULTS

There were 410,099 ophthalmic surgical procedures completed with a 25.3% overall increase over 10 years. Procedures were mostly government-funded (51%, n = 210,830) with 71% of patients aged over 64 years. Cataract surgery (78%, n = 318,564) had the highest mean SIR (703/100,000/year) and increased by 25% during the study period, consistent with population growth in the over 64 years old age group. Vitrectomy surgery had the second highest mean SIR (67/100,000/year) and increased by 50%, well above national population growth during the study period. Other SIRs included conjunctival lesion-biopsy (38/100,000/year), glaucoma (33/100,000/year), strabismus (20/100,000/year), dacryocystorhinostomy (10/100,000/year), and keratoplasty surgery (4/100,000/year).

CONCLUSIONS

This comprehensive review of New Zealand ophthalmic surgery reports increasing SIRs that cannot be explained by population growth alone. Cataract surgery numbers increased year on year consistent with the increase in the over 64 years old population. Vitrectomy surgery growth exceeded that of the national population, including those over 64 years.

Incidence and Clinical Characteristics of Postoperative Endophthalmitis After Ab-Interno Canaloplasty

Introduction

Postoperative endophthalmitis (POE) is a rare but devastating complication of ophthalmic surgeries. Microinvasive glaucoma surgery (MIGS) procedures have become increasingly utilized for the surgical reduction of intraocular pressure (IOP). Ab-interno canaloplasty (ABiC) is a popular MIGS procedure, but POE rates and clinical effects following ABiC have not been studied.

Methods

This study conducted a retrospective review of all consecutive cases of either standalone ABiC or combined ABiC with phacoemulsification performed at a tertiary care academic referral center from 2015 to 2021. Exclusion criteria included a history of incisional glaucoma surgery, retinal surgery, or additional concurrent microinvasive glaucoma surgery (MIGS) at the time of ABiC. The rates of POE after ABiC were calculated with 95% confidence intervals (CI) based on the Clopper-Pearson exact method.

Results

Of 3256 cases of ABiC, one case (0.03%, 1/3256, 95% CI: 0.00–0.17%) of post-ABiC endophthalmitis was identified. The rate of POE in standalone ABiC was 0.00% (0/1332 cases, 95% CI: 0.00–0.28%), whereas the rate in combined ABiC with phacoemulsification was 0.05% (1/1924 cases, 95% CI: 0.00–0.29%). Additionally, the rate of POE following stand-alone cataract surgery, 0.10%, 11/11,470 cases, 95% CI: 0.05–0.17%), total cataract surgeries, 0.06% (17/28,013 cases, 95% CI: 0.04–0.10%), total MIGs, excluding ABiC, surgeries, 0.08%, (3/3845 cases, 95% CI: 0.02–0.23%) portray non-inferiority of ABiC in the risk of POE. The case of ABiC-POE presented four days after surgery and required a vitreous tap with intraocular injection of antibiotics and pars plana vitrectomy. No causative organism was identified. A final 1-year follow-up revealed a corrected distance visual acuity of 20/40 and stable glaucoma.

Conclusion

The rate of POE after ABiC (1 per 3256 cases) is statistically non-inferior to the reported incidence of POE after other MIGS and incisional glaucoma surgeries.

Multicenter Effectiveness and Disease Stability Through 3 Years After iStentTrabecular Micro-Bypass with Phacoemulsification in Glaucoma and Ocular Hypertension

Purpose

To evaluate 3-year safety and efficacy of two second-generation trabecular micro-bypass stents. (iStent inject^®) with phacoemulsification.

Materials and Methods

This multicenter retrospective study of iStent inject implantation with phacoemulsification included data from eight surgeons across Australia. Eyes with cataract and mild to advanced glaucoma [predominantly primary open-angle (POAG), primary angle closure (PAC), or normal-tension (NTG) glaucoma] or ocular hypertension (OHT) were included. Study assessments included intraocular pressure (IOP); number of ocular hypotensive medications; proportions of eyes with 0, 1, 2, or ≥3 IOP-lowering medications; IOP ≤15 mmHg or ≤18 mmHg; visual fields (VF); retinal nerve fiber layer thickness (RNFL); central corneal thickness (CCT); intraoperative complications; adverse events; and secondary surgeries.

Results

A total of 273 eyes underwent surgery and had 36-month follow-up. At 36 months versus preoperative, mean IOP decreased by 15.5% (16.4±4.6 mmHg to 13.9±3.5 mmHg; p<0.001), and 70.3% of eyes achieved IOP of ≤15 mmHg (versus 49.1% preoperatively; p<0.001). The mean medication burden decreased by 68.5% (from 1.51±1.17 to 0.48±0.89 medications; p<0.001); 71.4% of eyes were medication-free (versus 21.6% preoperatively; p<0.001), while 6.2% of eyes were on ≥3 medications (versus 22.3% preoperatively; p<0.001); 96.3% of eyes maintained or reduced medications vs preoperative. Significant IOP and medication reductions occurred across glaucoma subtypes (POAG, PAC, NTG, OHT): 13–22% for IOP (p<0.05 for all) and 42–94% for medication (p<0.05 for all). Favorable safety included few adverse events; stable VF, RNFL, and CCT; and filtering surgery in only 8 eyes (2.9%) over 3 years.

Conclusion

In this multicenter cohort from 8 surgeons across Australia, significant IOP and medication reductions were sustained through 3 years after iStent inject implantation with phacoemulsification. Results were favorable across different glaucoma subtypes (including POAG, PAC, NTG, OHT), severities, and surgeons, thereby underscoring the real-world relevance and efficacy of iStent inject implantation for glaucoma treatment.

Treatment Success Across Different Levels of Preoperative Disease Burden: Stratified Two-Year Outcomes from the Pivotal Trial of iStent inject ® Trabecular Micro-Bypass in Primary Open-Angle Glaucoma and Cataract

PURPOSE

To examine effectiveness outcomes stratified by preoperative disease burden in the pivotal trial of iStent inject ® with cataract surgery (INJ) vs cataract surgery alone (CS).

MATERIALS AND METHODS

Prospective, 3:1 randomized, single-masked, concurrently-controlled, multicenter trial enrolling 505 subjects with cataract and mild-to-moderate primary open-angle glaucoma who underwent iStent inject implantation with phacoemulsification or phacoemulsification alone, and were followed for 2 years including annual medication washouts. Post hoc stratification was completed for baseline mean diurnal intraocular pressure (BL DIOP; Low-DIOP <25mmHg, Mid-DIOP ≥25 to <30 mmHg, High-DIOP ≥30mmHg) and preoperative medication burden (Low-Med 1 medication, Mid-Med 2 medications, High-Med ≥3 medications).

RESULTS

The 24-month primary and secondary effectiveness endpoints were met, with significant treatment-over-control differences in percent of eyes achieving ≥20% unmedicated DIOP reduction and in unmedicated DIOP reduction, respectively. In subgroup analyses, the proportions of INJ eyes achieving the primary endpoint remained steady across all BL DIOP (75.4%, 77.1%, 74.4% in Low/Mid/High-DIOP strata, respectively) and preoperative medication levels (76.8%, 70.8%, 79.7% in Low/Mid/High-Med strata, respectively); meanwhile, the proportions of CS eyes diminished with higher BL DIOP (64.5%, 63.6%, 33.3%, respectively) and more medications (69.0%, 63.3%, 29.4%, respectively). Regarding secondary effectiveness, postoperative DIOP reduction increased with higher BL DIOP in INJ eyes (6.2mmHg, 7.8mmHg, 9.8mmHg, respectively) but plateaued in CS eyes (5.2mmHg, 5.8mmHg, 5.4mmHg, respectively). INJ eyes also had consistent DIOP reduction regardless of preoperative medication burden (6.8mmHg, 6.7mmHg, 7.8mmHg, respectively), while DIOP reduction diminished with more medications in CS eyes (6.1mmHg, 5.0mmHg, 3.3mmHg, respectively). Safety was favorable, comparable to phacoemulsification alone.

CONCLUSION

Significant IOP reductions occurred across all levels of BL DIOP and preoperative medication burden in iStent inject eyes. DIOP reductions increased with higher BL DIOP and remained stable across all levels of preoperative medication burden, suggesting the device's potential utility in more medically challenging cases.

Two-Year Comparative Outcomes of First- and Second-Generation Trabecular Micro-Bypass Stents with Cataract Surgery

INTRODUCTION

This retrospective comparative study assessed real-world effectiveness and safety of first-generation (iStent®) and second-generation (iStent inject®) trabecular micro-bypass stents with cataract surgery in patients with open-angle glaucoma (OAG).

MATERIAL AND METHODS

Through a 24-month postoperative follow-up, the effectiveness was quantified by intraocular pressure (IOP) reduction; mean glaucoma medication reduction; proportional analysis of eyes meeting IOP cutoffs (<18, <15, <12 mmHg) either with or without medications; and proportional analysis of medication burden. Safety measures included visual acuity, adverse events, and secondary surgery.

RESULTS

A total of 82 consecutive eyes (39 iStent, 43 iStent inject) with a 24-month follow-up were analyzed. Most eyes (74.4%) had primary open-angle glaucoma, with the remainder having pseudoexfoliative or pigmentary glaucoma; all eyes had mild-to-moderate disease. At 24 months postoperative, the mean IOP was lower, and the percent reduction from baseline was greater, in iStent inject eyes (26.0% reduction, 17.7mmHg to 13.1mmHg) than in iStent eyes (9.8% reduction, 16.4mmHg to 14.8mmHg) (between-groups comparison, p=0.019). Within each group, the postoperative IOP reduction was greater in eyes with higher baseline IOP (p<0.001). Medication burden decreased significantly in both groups, from 1.74 to 0.51 mean medications for iStent (70.7% reduction, p<0.0001), and 2.19 to 0.65 for iStent inject (70.3% reduction, p<0.0001). Both groups exhibited excellent safety.

CONCLUSION

iStent or iStent inject with phacoemulsification produced significant IOP and medication reductions, with effects enduring for two years. IOP reductions were greater for iStent inject than for iStent. Within each group, higher preoperative IOP was associated with greater postoperative IOP reduction.