Glaukos iStent Trabecular Micro-Bypass

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.

Clinical and Visual Field Outcomes Following Minimally Invasive Glaucoma Surgery Combined with Cataract Surgery

Purpose

To determine the change in Humphrey visual field and clinical parameters after minimally invasive glaucoma surgery combined with cataract surgery.

Patients and Methods

Patients undergoing minimally invasive glaucoma surgery combined with cataract surgery in a multicenter retrospective case series between 2013 and 2021 with reliable preoperative and 12 to 18 month postoperative visual field measurements were included. Devices included iStent, XEN, and Hydrus. Clinical parameters were compared with a generalized linear model with generalized estimating equations between preoperative and postoperative visits including best corrected visual acuity, intraocular pressure, number of glaucoma medications and visual fields. Visual field metrics included mean deviation (MD), pattern standard deviation (PSD), visual field index (VFI), and Collaborative Initial Glaucoma Treatment Study (CIGTS) score of total deviation probability and pattern deviation probability.

Results

Forty-four eyes from 39 patients were included. During the follow up period, visual acuity improved from 0.23±0.17 to 0.10±0.14 logMAR (mean ± standard deviation, p<0.001), number of glaucoma medications was reduced from 2.68±1.06 to 1.46±1.32 (p<0.001), and intraocular pressure decreased from 17.08±4.23 mmHg to 14.92±3.13 mmHg (p=0.003). Differences across devices were negligible. The only significant difference was a greater reduction in number of glaucoma medications in the XEN group (p<0.001). There were no significant changes in the global parameters of VFI, MD, PSD, or CIGTS.

Conclusion

Overall, minimally invasive glaucoma surgery combined with cataract surgery appears to be effective at stabilizing visual field function, reducing intraocular pressure, reducing number of glaucoma medications, and improving visual acuity over a 12 to 18 month follow-up period across MIGS devices.

Outcomes of combined single-use dual blade goniotomy and cataract surgery

Purpose

Single-use dual blade goniotomy (SBG) is a novel ab interno procedure that removes three to five clock hours of trabecular meshwork (TM). We analysed the reduction of intraocular pressure (IOP) and topical glaucoma medication (Meds) in eyes following combined cataract surgery and SBG (Cat-SBG).

Methods

IOP and Meds were evaluated retrospectively in 55 eyes of 38 patients. 44 eyes had high tension glaucoma (HTG) and eleven eyes had normal tension glaucoma (NTG). Complete success (no Meds) and qualified success (with Meds) for IOP levels ≤ 21, ≤ 18 , ≤ 16 mmHg or ≥ 20% IOP reduction at the two- and six-month follow-up were evaluated.

Results

IOP and Meds were significantly reduced from before to two months after Cat-SBG in HTG- and NTG-patients (HTG: IOP 19.4 ± 3.3 to 15.1 ± 3.3 mmHg; p < 0.001; Meds 2.1 ± 1.3 to 0.8 ± 1.3; p < 0.001; NTG: IOP 14.0 ± 2.3 to 11.5 ± 2.3 mmHg; p = 0.004; Meds 1.6 ± 0.7 to 0.3 ± 0.7; p < 0.001). IOP and Meds did not change significantly from two to six months after Cat-SBG.

In HTG, complete and qualified success rates were 43% (19/44) and 93% (41/44) for IOP ≤ 18 mmHg, 36% (16/44) and 64% (28/44) for IOP ≤ 16 mmHg and 30% (13/44) and 43% (19/44) for ≥ 20% IOP reduction six months after surgery. In NTG, complete and qualified success was 81% (9/11) and 100% (11/11) for IOP ≤ 18 and ≤ 16 mmHg, and 27% (3/11) for IOP reduction ≥ 20%.

IOP and Meds reduction were comparable between HTG and NTG eyes.

Only minor postoperative complications occurred.

Conclusion

Cat-SBG is an efficient method to significantly lower IOP in patients with HTG and NTG.

Efficacy of Selective Laser Trabeculoplasty after iStent Implantation in Primary Open-Angle Glaucoma

iStent implantation is thought to augment the trabecular outflow channel in the anterior segment of the eye. We hypothesized that iStent with subsequent selective laser trabeculoplasty (SLT) would better control the intraocular pressure (IOP) compared to standalone SLT in patients with primary open-angle glaucoma (POAG). We, therefore, determined if the presence of an iStent combined with SLT was statistically associated with IOP lowering compared to standalone SLT. Through retrospective electronic medical record review, records of 824 eyes from 440 patients who received primary SLT without a history of iStent were considered. Additionally, 42 eyes from 28 patients who received SLT after combined phacoemulsification and iStent implantation that failed to control intraocular pressure (IOP) and/or the progression of the disease were retrospectively reviewed. IOP and number of medications, which were tracked in each patient for up to 12 months post laser, were also examined. Successful outcome was defined as a statistically significant reduction in IOP or number of medications at 6 months. As defined in univariate analysis (p ≤ 0.01), multivariate analysis included iStent, age, sex, race, and initial IOP as variables. IOP reduction was statistically associated with patients pre-SLT IOP (p < 0.001) but not with patients with iStent (p = 0.222). Medication reduction was statistically associated with the pre-SLT number of medications (p < 0.001) and iStent (p < 0.001). In eyes that received SLT, iStent was not statistically associated with a greater reduction in IOP compared to controls, but was associated with a higher reduction in the overall number of medications used 6 months after receiving SLT. The work presented should guide clinicians to consider SLT as an effective therapy after iStent implantation, in terms of glaucoma medication reduction in iStent patients, but clinicians should know that the presence of an iStent does not necessarily make subsequent SLT more effective at lowering IOP.

Outcomes of Combined iStent Trabecular Micro-Bypass and Cataract Surgery for the Treatment of Open-Angle Glaucoma in a Saudi Population

Purpose

To assess the effectiveness and safety of a single iStent trabecular micro-bypass stent implantation in combination with cataract surgery in lowering the intra ocular pressure (IOP) and number of anti-glaucoma medications in Saudi patients with open-angle glaucoma (OAG).

Setting

King Fahad Hospital of the University, Al Khobar, Saudi Arabia.

Design

Prospective, non-comparative, uncontrolled, non-randomized interventional case series.

Methods

One iStent was implanted during phacoemulsification cataract surgery for adult patients with OAG by a single surgeon over a period of 3 years. Main outcome measures include number of anti-glaucoma medications, IOP, corrected distance visual acuity (CDVA) and complications.

Results

Thirty-six eyes of 33 patients with OAG underwent the surgery. The pre-operative mean IOP and mean anti-glaucoma medications were 17.47 ± 5.44 mmHg and 2.69 ± 0.92, respectively. At 1 year of follow-up mean, IOP decreased to 13.44 ± 1.99 (23.1% reduction) (P<0.001) and mean anti-glaucoma medications decreased to 1.47±1.13 (45.4% reduction) (P<0.001).

Conclusion

After 12-month follow-up, phacoemulsification with the implantation of a single iStent seems to be an effective and safe procedure to lower IOP and the number of anti-glaucoma medications, and to overcome the problems associated with medication nonadherence in OAG patients with cataracts.

A comparison of the 1-year surgical outcomes of ab externo trabeculotomy and microhook ab interno trabeculotomy using propensity score analysis

Objective

To compare the 1-year outcomes of trabeculotomy ab externo (ab externo TLO) and trabeculotomy ab interno using a microhook (ab interno TLO) for glaucoma patients using propensity score analysis.

Methods and analysis

The medical charts of 65 consecutive patients who underwent ab externo TLO and those of 69 patients who underwent ab interno TLO were reviewed. Logistic regression analysis was conducted to calculate the propensity score using 1:1 matched analysis, which indicates the likelihood of surgical success at 12 months. We set the outcome-related covariates as age, glaucoma type, mean deviation, preoperative intraocular pressure (IOP), the number of preoperative glaucoma eye drops and the presence or absence of combined cataract surgery. Fifty eyes per each surgery group were subsequently compared.

Results

The mean preoperative IOP was 32.5±11.2 mm Hg in the ab externo TLO group and 28.4±7.8 mm Hg in the ab interno TLO group (p=0.08). The mean postoperative IOP at 12 months was 18.3±7.4 mm Hg in the former group and 17.8±6.3 mm Hg in the latter (p=0.91). When surgical success was defined as a postoperative IOP of between 5 and 21 mm Hg with a more than 20% IOP reduction from baseline and no additional glaucoma surgery, the rate at 12 months was 78% in the ab externo TLO group and 74% in the ab interno TLO group (p=1.00).

Conclusion

The 1-year success rate was not significantly different between ab externo and ab interno TLO.

Comparing iStent versus CyPass with or without phacoemulsification in patients with glaucoma: a meta-analysis

Bacground

The aim of this study was to conduct a meta-analysis to compare the overall intraocular pressure (IOP)-lowering effect of iStent or CyPass as isolated procedures or in combination with cataract extraction.

Materials and methods

Cochrane review manager 5.3 software (RevMan^® 5.3) was used for a meta-analysis of IOPs and the number of antiglaucoma medications in six groups according to the type and number of stents and whether the procedure was isolated or in combination with cataract extraction.

Main results

A total of 33 out of 446 publications retrieved have been enrolled. The mean changes in IOP in the groups with one iStent and more than two iStents with concurrent cataract extraction were -3.78 ± 0.53 mmHg and -3.89 ± 0.73 mmHg, respectively. The mean differences in IOP in the groups with one iStent and more than two iStents without concurrent cataract extraction were -3.96 ± 0.25 mmHg and -7.48 ± 0.55 mmHg, respectively. The mean changes in IOP in the groups with CyPass implantation with and without concurrent cataract extraction were -4.97 ± 1.38 mmHg and -8.96 ± 0.16 mmHg, respectively.

Conclusions

Both iStent and CyPass either in combination with cataract extraction or as isolated procedures effectively decrease IOP. This effect is greatest with isolated implantation of CyPass followed by multiple iStents and then single iStent implantation and lasts up to 2 years.

Ab interno canaloplasty for the treatment of glaucoma: a case series study

Purpose

To describe and evaluate the efficacy of ab interno canaloplasty (ABiC) in patients with primary open-angle glaucoma (POAG).

Methods

This single-center consecutive case series study included patients with cataract and open-angle glaucoma (combined procedure) and pseudophakic patients (mean age, 76 years; range, 66–83 years) with POAG who underwent ABiC using the iTrack™ 250-μm microcatheter (Ellex Medical Lasers Pty Ltd, Adelaide, Australia) to circumferentially viscodilate and intubate Schlemm’s canal without placement of a tensioning suture. The primary endpoints were mean intraocular pressure (IOP) and mean number of glaucoma medications at 1, 3, 6, 9, and 12 months postoperatively.

Results

In total, 20 patients (20 eyes) were enrolled in the study. Mean IOP reduced from 18.5 ± 3.44 mm Hg preoperatively to 14.88 ± 2.82 mm Hg (n = 17), 13.80 ± 2.05 (n = 12), 14.57 ± 2.59 mm Hg (n = 9) and 15.47 ± 2.42 (n = 6) at 1, 3, 6 and 9 months postoperatively. The 12‑month data for two patients showed that IOP had reduced from 17 mm Hg preoperatively to 16 mm Hg in one patient and from 20 mm Hg to 13 mm Hg in the other patient. The mean number of medications was reduced from 2.4 preoperatively to 0.25 at the last follow-up visit. There was one reported complication of limited descemetolysis near the limbus by the viscoelastic during the dilatation of Schlemm’s canal. No adverse events as a result of the device were reported.

Conclusions

ABiC was straightforward to perform in this group of patients with minimal complications. Although initial findings from this study indicate that ABiC is comparable to conventional canaloplasty in lowering IOP and medication dependency, long-term follow-up in a large patient cohort is required to confirm the efficacy of this minimally invasive glaucoma procedure.

Efficacy and Adverse Event Profile of the iStent and iStent Inject Trabecular Micro-bypass for Open-angle Glaucoma: A Meta-analysis

Aim

This meta-analysis explores the efficacy and adverse event profile of the iStent, an ab interno implant for the treatment of open-angle glaucoma.

Methods

A systematic literature search of Ovid MEDLINE and EMBASE was used to identify peer-reviewed original studies that provided efficacy data on the first or second generation iStent for at least five eyes. Intraocular pressure (IOP) was the primary efficacy endpoint, while the number of medication classes was the secondary outcome. Weighted mean differences were reported for continuous endpoints, while a relative risk was computed for dichotomous variables.

Review Results

The search revealed 545 results, of which 1767 eyes from 28 studies were included. The cohort age was 71.4 ± 5.4 years, and 44.9% of patients were male. There was a significantly greater IOP reduction after the use of two first-generation stents compared to one, irrespective of phacoemulsification status (p < 0.001). Additionally, there was a significantly greater IOP reduction following iStent alone relative to phaco-iStent for the first-generation iStent (p < 0.001) and the iStent inject (p < 0.001). For the first generation stent, combined phaco-iStent provided a greater level of IOP reduction (p < 0.001) and reduction in the number of medication classes relative to phacoemulsification alone (p < 0.001). In total, 22.5% of eyes that received iStent implantation sustained some type of adverse event. The most common adverse events were intraocular pressure elevation, stent blockage or obstruction, stent malposition and hyphema.

Conclusion and Clinical Significance

Statistically significant differences in efficacy outcomes exist between different numbers of stents and the presence or absence of concurrent phacoemulsification.

How to cite this article: Popovic M, Campos-Moller X, Saheb H, Ahmed IIK. Efficacy and Adverse Event Profile of the iStent and iStent Inject Trabecular Micro-bypass for Open-angle Glaucoma: A Meta-analysis. J Curr Glaucoma Pract 2018;12(2):67-84.

Evaluation of Bleb Morphology and Reduction in IOP and Glaucoma Medication following Implantation of a Novel Gel Stent

Objective

To evaluate the efficacy and safety of the Xen Gel Stent and provide a macro- and microscopic analyses of bleb morphology.

Methods

A prospective 12-month study on patients with primary open-angle glaucoma. Patients underwent implantation of the XEN Gel Stent (Allergan INC, Dublin, Ireland) either alone or combined with a cataract surgery. Biomicroscopy, in vivo confocal microscopy (IVCM), and anterior segment-optical coherence tomography (AS-OCT) were used to assess bleb morphology. Safety parameters were adverse events, best corrected visual acuity, visual field, and corneal endothelial cell loss. A postoperative IOP ≤ 18 mmHg without or on medications was respectively defined as complete and qualified success while an IOP ≥ 18 mmHg was defined as failure.

Results

Twelve eyes of 11 patients were evaluated. At one year, 5 out of 10 patients available achieved a complete success while five were qualified success. AS-OCT showed that bleb wall reflectivity was significantly higher in the failure group; IVCM revealed that stromal density was significantly lower in the success group. No safety issues were recorded.

Conclusion

Implantation of the XEN Gel Stent appears to be a safe and effective procedure. AS-OCT and IVCM may be helpful in bleb assessment.

Differential Canalograms Detect Outflow Changes from Trabecular Micro-Bypass Stents and Ab Interno Trabeculectomy

Recently introduced microincisional glaucoma surgeries that enhance conventional outflow offer a favorable risk profile over traditional surgeries, but can be unpredictable. Two paramount challenges are the lack of an adequate training model for angle surgeries and the absence of an intraoperative quantification of surgical success. To address both, we developed an ex vivo training system and a differential, quantitative canalography method that uses slope-adjusted fluorescence intensities of two different chromophores to avoid quenching. We assessed outflow enhancement by trabecular micro-bypass (TMB) implantation or by ab interno trabeculectomy (AIT). In this porcine model, TMB resulted in an insignificant (p > 0.05) outflow increase of 13 ± 5%, 14 ± 8%, 9 ± 3%, and 24 ± 9% in the inferonasal, superonasal, superotemporal, and inferotemporal quadrant, respectively. AIT caused a 100 ± 50% (p = 0.002), 75 ± 28% (p = 0.002), 19 ± 8%, and 40 ± 21% increase in those quadrants. The direct gonioscopy and tactile feedback provided a surgical experience that was very similar to that in human patients. Despite the more narrow and discontinuous circumferential drainage elements in the pig with potential for underperformance or partial stent obstruction, unequivocal patterns of focal outflow enhancement by TMB were seen in this training model. AIT achieved extensive access to outflow pathways beyond the surgical site itself.

Canaloplasty: A Minimally Invasive and Maximally Effective Glaucoma Treatment

Canaloplasty is a highly effective, minimally invasive, surgical technique indicated for the treatment of open-angle glaucoma that works by restoring the function of the eye's natural outflow system. The procedure's excellent safety profile and long-term efficacy make it a viable option for the majority of glaucoma patient types. It can be used in conjunction with existing drug based glaucoma treatments, after laser or other types of incisional surgery, and does not preclude or affect the outcome of future surgery. Numerous scientific studies have shown Canaloplasty to be safe and effective in lowering IOP whilst reducing medication dependence. A recent refinement of Canaloplasty, known as ab-interno Canaloplasty (ABiC), maintains the IOP-lowering and safety benefits of traditional (ab-externo) Canaloplasty using a more efficient, simplified surgical approach. This paper presents a review of Canaloplasty indications, clinical data, and complications, as well as comparisons with traditional incisional glaucoma techniques. It also addresses the early clinical evidence for ABiC.

iStent with Phacoemulsification versus Phacoemulsification Alone for Patients with Glaucoma and Cataract: A Meta-Analysis

Background

Minimally invasive glaucoma surgeries (MIGS) have attracted significant attention, as they have been reported to lower intra-ocular pressure (IOP) and have an excellent safety profile. The iStent is an example of a minimally invasive glaucoma device that has received particular attention due to its early and wide spread utilization. There is a growing body of evidence supporting its use at the time of phacoemulsification to help lower IOP. However, it is still not clear how much of the IOP lowering effect can be attributed to the iStent, the crystalline lens extraction or both when inserted concurrently at the time of phacoemulsification. This has been an important issue in understanding its potential role in the glaucoma management paradigm.

Purpose

To conduct a systematic review and meta-analysis comparing the IOP lowering effect of iStent insertion at the time of phacoemulsification versus phacoemulsification alone for patients with glaucoma and cataracts.

Methods

A systematic review was conducted utilizing various databases. Studies examining the IOP lowering effect of iStent insertion in combination with phacoemulsification, as well as studies examining the IOP lowering effect of phacoemulsification alone were included. Thirty-seven studies, reporting on 2495 patients, met the inclusion criteria. The percentage reduction in IOP (IOPR%) and mean reduction in topical glaucoma medications after surgery were determined. The standardized mean difference (SMD) was computed as a measure of the treatment effect for continuous outcomes taking into account heterogeneity. Fixed-effect and random-effect models were applied.

Results

A 4% IOP reduction (IOPR%) from baseline occurred following phacoemulsification as a solo procedure compared to 9% following an iStent implant with phacoemulsification, and 27% following 2 iStents implants with phacoemulsification. Compared with cataract extraction alone, iStent with phacoemulsification resulted in significant reduction in the post-operative IOP (IOPR%) (SMD = -0.46, 95% CI: [-0.87, -0.06]). A weighted mean reduction in the number of glaucoma medications per patient was 1.01 following phacoemulsification alone compared to 1.33 after one iStent implant with phacoemulsification, and 1.1 after 2 iStent implants with phacoemulsification. Compared to cataract extraction alone, iStent with cataract extraction showed a significant decrease in the number of glaucoma medications (SMD = -0.65, 95% CI: [-1.18, -0.12]). Funnel plots suggested the absence of publication bias.

Conclusion

Both iStent implantation with concurrent phacoemulsification and phacoemulsification alone result in a significant decrease in IOP and topical glaucoma medications. In terms of both reductions, iStent with phacoemulsification significantly outperforms phacoemulsification alone.

iStent as a Solo Procedure for Glaucoma Patients: A Systematic Review and Meta-Analysis

BACKGROUND

Glaucoma is a leading cause of irreversible blindness. It is firmly entrenched in the traditional treatment paradigm to start with pharmacotherapy. However, pharmacotherapy is not benign and has been well documented to have a number of significant challenges. Minimally invasive glaucoma surgery (MIGS) that targets the outflow pathway with minimal to no scleral dissection has resulted in the need to reconsider the glaucoma treatment paradigm.

PURPOSE

To perform a systematic review and meta-analysis to evaluate and quantify the effect on post-operative intraocular pressure (IOP) and number of topical glaucoma medications, in patients receiving the iStent MIGS device as the solo procedure without concurrent cataract surgery.

METHODS

A systematic review was conducted by searching various databases between January 1, 2000, and June 30, 2014. Studies reporting up to a maximum follow-up period of 24 months were retrieved and screened using the EPPI-Reviewer 4 gateway. Percentage reduction in IOP (IOPR%), and mean reduction in topical glaucoma medications after surgery were computed. Meta-analysis was performed using STATA v. 13.0. The standardized mean difference (SMD) was calculated as the effect size for continuous scale outcomes. Heterogeneity was determined using the I2 statistics, Z-value, and χ2 statistics. Fixed-effect and random-effect models were developed based on heterogeneity. Sub-group analysis was performed based on the number of iStents implanted and the follow-up period. The outcome measures were changes in the IOP and number of glaucoma medications.

RESULTS

The search strategy identified 105 records from published literature and 9 records from the grey literature. Five studies with 248 subjects were included for quantitative synthesis. A 22% IOP reduction (IOPR%) from baseline occurred at 18-months after one iStent implant, 30% at 6-months after two iStents implantations, and 40% at 6-months after implantation of three iStents. A mean reduction of 1.2 bottles per patient of topical glaucoma medications occurred at 18-months after one iStent implant, 1.45 bottles per patient at 6-months after two iStents, and one bottle of medication per patient was reduced at 6-months following placement of three iStents implants. Meta-analysis results showed a significant reduction in the IOP after one iStent (SMD = -1.68, 95% CI: [-2.7, -0.61]), two iStents (SMD = -1.88, 95% CI: [-2.2, -1.56]), and three iStents (SMD = -2, 95% CI: [-2.62, -1.38]) implantation. Results showed a significant drop in the topical glaucoma medications after one iStent (SMD = -2.11, CI: [-3.95, -0.27]), two iStent (SMD = -1.88, CI: [-2.20, -1.56]), and three iStents (SMD = -2.00, CI: [-2.62, -1.38]) implantation. The maximum reduction in IOP occurred at 12-months (SMD = -2.21, CI: [-2.53, -1.88]) and a significant reduction in post-operative topical glaucoma medications occurred even after 18-months of iStent implantation (SMD = -0.71, CI: [-1.15, -0.26]).

CONCLUSION

iStent implantation as a solo procedure without concurrent cataract extraction does lower IOP, and reduces the dependency on glaucoma medications. This effect seems to last at least 18 months.

Trabecular micro-bypass shunt (iStent®): basic science, clinical, and future)

The trabecular bypass stent offers an alternative to filtration surgery. Patients who may be ideal candidates for considering this procedure are those with prior conjunctival surgery; for example, those who had a 360° peritomy from a scleral buckle might not do well with a trabeculectomy and there is no space for a tube. Highly myopic patients do not tolerate hypotony well, and the iSTB may be an option for some of these patients. I have used the iSTB in patients on anticoagulants who could not stop them, and they needed something beyond medications and laser to lower the IOP in subjects with open-angle glaucoma. Young patients, especially those with one eye, who need rapid visual recovery (for instance to return to work) may be good candidates to consider the iSTB as well. Because of the position used for clear corneal cataract surgery, the temporal approach is best for doing these. Therefore, if you are doing cataract surgery on someone who needs a lower IOP, you already are in the correct position to implant the devices. Patients may need some medications after the procedure to lower the IOP to the level desired. The results from Armenia are encouraging, given an IOP of 11.8 mmHg after 2 iSTB stents and taking daily travoprost. These results are difficult to reach even with a trabeculectomy. When selecting your fist patients, avoid those with the congested episcleral veins, look for patients with wide open angles, and if you can see aqueous veins at the slit-lamp it may indicate a viable outflow system. Probably avoid patients with IOPs over 35 mmHg. The micro-invasive trabecular bypass stents offer an alternative surgical intervention for select patients with open-angle glaucoma. Recent studies show that combining these micro-stents with medications can lead to as low of an intraocular pressure (IOP) as is achieved by many more invasive incisional surgeries. The technique is quite precise and learning the procedure is similar to clear corneal phacoemulsification followed by a goniotomy. Long-term data are starting to come in and the safety is favorable. The IOP success appears to be based on the patency of the outflow system for a given patient. Key factors in determining the success involve the placement of trabecular bypass devices into the canal of Schlemm and require a down-stream patency of the collector channel system and a low episcleral venous pressure. Because accessing the collector system may require placement by a patent channel, the placement of two stents, a longer stent with scaffolding or somehow imaging the outflow system may lead to the best control of the IOP.

Techniques and outcomes of minimally invasive trabecular ablation and bypass surgery

Minimally invasive glaucoma surgeries (MIGS) can improve the conventional, pressure-dependent outflow by bypassing or ablating the trabecular meshwork (TM), or creating alternative drainage routes into the suprachoroidal or subconjunctival space. They have a highly favourable risk profile compared to penetrating surgeries, and lower intraocular pressure with variable efficacy that may depend on the extent of outflow segments accessed. Since they are highly standardised procedures that use clear corneal incisions, they can elegantly be combined with cataract and refractive procedures to improve vision in the same session. There is a growing need for surgeons to become proficient in MIGS to address the increasing prevalence of glaucoma and cataracts in a well-informed, aging population. Techniques of visualisation and instrumentation in an anatomically highly confined space with semitransparent tissues are fundamentally different from other anterior segment surgeries, and present even experienced surgeons with a substantial learning curve. Here, we provide practical tips, and review techniques and outcomes of TM bypass and ablation MIGS.

A history of the surgical management of glaucoma

Many new surgeries have been devised since 1856, when von Graefe discovered that iridectomy is an effective surgical method for acute glaucoma treatment. Two years later, De Wecker presented sclerotomy as a procedure for chronic glaucoma. In 1900, internal filtration (cyclodialysis) was developed. In 1932, ciliodestruction was suggested. The four approaches, relief of pupillary block, external filtration, internal filtration, and ciliodestruction, are still the basic techniques of glaucoma surgeries over 100 years later. There have been two basic approaches to lowering eye pressure surgically: increase outflow and decrease inflow of aqueous humor. Although the majority of surgeries used nowadays were introduced in the 1960s, their roots can be traced to the work of surgeons in the 19th century. Trabeculectomy, in use since the mid-1960s, is the most effective glaucoma surgery in terms of intraocular pressure reduction but carries its own limitations. Non-penetrating glaucoma surgeries emerged at the same time trabeculectomy was presented, but they are not used as commonly as trabeculectomy. Molteno introduced the first effective shunt and followed by others. Since 1995, the majority of new surgeries have consisted of new implantable devices including SOLX, iStent, and Ex-PRESS shunt. This article will review the history of glaucoma surgery and describe the fundamentals of different glaucoma procedures.

Imaging modalities for localization of an iStent(®)

The iStent (Glaukos Corporation, Laguna Hills, CA) is a 1-mm, titanium trabecular bypass stent implanted across the inner wall of Schlemm's canal under direct gonioscopy. This study was designed to determine the best modality to identify iStent placement when gonioscopic visualization is not possible. In this in vitro study on a human cadaver eye, ultrasound biomicroscopy (UBM), anterior segment optical coherence tomography (AS-OCT), and B-scan ultrasonography were done to visualize and precisely locate two intentionally misplaced iStents. UBM could localize both intentionally misplaced stents, whereas AS-OCT could not visualize the iStent that was lodged in the sulcus. B-scan ultrasonography was unable to detect either of the stents. UBM may be a useful imaging modality to identify iStent in the anterior or posterior chamber, whereas AS-OCT is limited to detection of stents in the anterior chamber alone. B-scan ultrasonography is unable to identify iStent in either the anterior or posterior chamber.