Canaloplasty using iTrack 250 Microcatheter with Suture Tensioning on Schlemm's Canal

Ten-Year Results After Canaloplasty and Phacocanaloplasty

Background/Objectives: To evaluate the long-term efficacy and safety of canaloplasty and phacocanaloplasty in patients with primary open-angle glaucoma (POAG) and pseudoexfoliation glaucoma (PEXG). Methods: This retrospective observational study included 85 patients with POAG and PEXG who underwent canaloplasty (group 1) or phacocanaloplasty (group 2). Every patient had complete medical records over a 10-year follow-up period. The primary endpoints were the pressure-lowering and drug-sparing effects. The secondary endpoints were intra- and postoperative complications as well as the need for additional surgical interventions. Results: In group 1, the mean baseline intraocular pressure (IOP) of 22.1 ± 0.9 mmHg was reduced to 15.3 ± 0.5 mmHg, 15.7 ± 0.5 mmHg, and 15.9 ± 0.7 mmHg at 1, 5, and 10 years, respectively. The mean medication use decreased from 2.4 ± 1.0 before surgery to 0.1 ± 0.5, 0.8 ± 1.1, and 1.4 ± 1.3 at 1,5, and 10 years, respectively. In group 2, IOP was reduced from 20.4 ± 1.5 to 15.6 ± 1.0, 14.3 ± 0.8, and 14.2 ± 1.2 at 1, 5, and 10 years, respectively. The mean medication use dropped from 2.4 ± 1 to 0.3 ± 0.9, 0.9 ± 1.4, and 0.8 ± 1.1 at 1,5, and 10 years, respectively. Goniopuncture was performed postoperatively in nine cases (13.9%) within the initial 3 months due to IOP spikes (POAG n = 6, PEXG n = 3). Patients with PEXG had a significantly higher likelihood of requiring re-operation (HR = 5.11, HR = 5.11, 95% CI 1.05-24.74, p = 0.043). No serious complications were observed. Conclusions: Canaloplasty is a safe and effective procedure for lowering IOP in eyes with POAG and PEXG, achieving approximately a 30% reduction in IOP. PEXG patients are likelier to have IOP spikes in the late postoperative period therefore careful monitoring and management is required.

Outcomes of Gonioscopy-Assisted Transluminal Trabeculotomy in Eyes With Prior Failed Glaucoma Surgery

PRCIS

This study concludes that GATT can be an effective and safe surgical alternative for managing IOP in eyes with prior failed glaucoma surgeries, associated with minimal complications.

PURPOSE

To report outcomes of gonioscopy-assisted transluminal trabeculotomy (GATT) in eyes with prior failed glaucoma surgery.

PATIENTS AND METHODS

A retrospective study involving 30 eyes of 30 patients, all of whom had open angles on gonioscopy, experienced prior glaucoma surgery failures, and subsequently underwent GATT. The primary outcome measure was success defined as complete when the intraocular pressure (IOP) was >5 and ≤21/16 mm Hg without glaucoma medications and qualified with medications.

RESULTS

The mean age was 51.8±16.1 years. Twenty-one eyes underwent GATT and 9 eyes underwent phaco-GATT. Twenty-seven eyes had failed trabeculectomy and 3 eyes had failed glaucoma drainage device. Post-GATT, the IOP decreased from 27.1±7 to 16.9±6 mm Hg (P<0.001) at the end of 15 months, with a mean drop in AGM from 4.9±1.0 to 2±1.6. At postoperative 1 year, the probability of complete success was 20% (95% CI: 9-43) for an IOP criterion of both 21 and 16 mm Hg. The qualified success probability at 1 year was 82% (67-100) for an IOP criterion of 21 mm Hg and 57% (38-84) for an IOP criterion of 16 mm Hg. Risk factor for failure was older age [hazard ratio (HR): 1.03, 95% CI: 1.01-1.06]. The complications noted were hyphema in 14 eyes (46%), majority resolved within 1 week and all by 2 weeks. None needed any intervention.

CONCLUSIONS

This study concludes that GATT can be an effective and safe surgical alternative for managing IOP in eyes with prior failed glaucoma surgeries, associated with minimal complications.

Alternative application of an iTrack microcatheter and canaloplasty: case report and literature review

INTRODUCTION

Glaucoma is the leading cause of irreversible blindness worldwide. Schlemm's canal surgery using an iTrack flexible microcatheter has become popular because of its high quality-of-life issues and the growing demand for less invasive but effective procedures. The unique design of the microcatheter makes it a multimodal tool, which can be used not only in the field of antiglaucoma surgery but also as a drug delivery system to treat various conditions.

AREAS COVERED

This review presents an update on the selected aspects of a drug delivery system using the iTrack microcatheter, including glaucoma gene therapy and posterior-segment diseases, both in animal models and human patients. The authors also report the case of a patient with branch retinal vein occlusion treated with suprachoroidal bevacizumab in the submacular region administered with the iTrack catheter.

EXPERT OPINION

The findings presented in this study may indicate that the application of a microcatheter in open-angle glaucoma gene therapy is reasonable and can be combined with full or partial surgical canaloplasty procedures. Translation of this potential into a treatment modality would require overcoming multiple barriers.

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.

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.

Clinical Results of Ab Interno Canaloplasty in Patients with Open-Angle Glaucoma

Purpose

To report treatment outcomes of ab interno canaloplasty using the Visco360 and Omni system devices as a standalone procedure or combined with cataract surgery in patients with open-angle glaucoma (OAG).

Design

Retrospective, single-center, consecutive case series.

Study Patients

Eighty-nine eyes of 64 patients aged 43 to 91 with open-angle glaucoma treated with ab interno canaloplasty between January 2018 and September 2019. Eyes with previous incisional glaucoma surgery and eyes with less than 90 degrees of viscodilation were excluded.

Intervention

Patients underwent ab interno canaloplasty as a stand-alone procedure or in conjunction with cataract surgery. Ab interno canaloplasty was performed with either the Visco360 or Omni System devices (Sight Sciences, Menlo Park, CA). Treatment consisted of viscodilation without trabeculotomy.

Main Outcome Measures

Primary outcome measures were mean IOP and mean number of glaucoma medications. Additional analysis included the impact of degrees of treatment on treatment outcomes.

Results

Preoperative mean IOP was 24.5 ± 8.3; the number of preoperative glaucoma medications was 2.5 ± 1.3. At 18 months postoperative, the mean IOP was reduced 36% to 15.8 ± 2.5 (P<0.001) and glaucoma medications were reduced 32% to 1.7 ± 1.5 (P<0.05). Higher preoperative IOP was significantly correlated with increased IOP lowering. Reduction of mean IOP and medications were not significantly different between standalone ab interno canaloplasty vs cataract surgery/ab interno canaloplasty. Reduction of mean IOP and medications were not significantly different between patients with 180 degrees of treatment vs 360 degrees of treatment.

Conclusion

Ab interno canaloplasty reduces IOP and glaucoma medication use in patients with OAG whether as a standalone surgery or in combination with cataract surgery.

Improvement of the Safety Profile of Canaloplasty and Phacocanaloplasty: A Review of Complications and Their Management

Research on the methods used to achieve persistent and safe control of intraocular pressure resulted in the implementation of novel surgical procedures, such as canaloplasty and phacocanaloplasty. Herein, we review the literature focused on the safety profile of canaloplasty and phacocanaloplasty and the management of related complications. The aim of canaloplasty is to restore the natural aqueous outflow. This goal is achieved via a surgical procedure that involves viscocanalostomy with catheterisation of Schlemm's canal (360°) and placement of a circumferential suture that tensions the canal walls. This improves Schlemm's canal drainage, choroidoscleral flow, and subconjunctival filtration. The efficacy of canaloplasty for reducing the intraocular pressure is similar to those of trabeculectomy with mitomycin C and deep sclerectomy augmented with an implant and mitomycin C. However, canaloplasty is associated with a lower complication rate than those conventional techniques. Novel microsurgical techniques for the treatment of glaucoma are unlikely to replace the conventional methods. However, these new techniques offer alternatives, especially for patients who have an early indication for surgical intervention. Nevertheless, canaloplasty is associated with the expectations of efficient, safe, and modern surgical treatment.

Modified Deep Sclerectomy for the Surgical Treatment of Glaucoma

Purpose:

To report the short-term outcomes of modified deep sclerectomy (MDS) in the management of open angle glaucoma.

Methods:

This prospective, non-randomized, controlled study included 105 eyes (105 patients) with open angle glaucoma. Eyes were categorized as follows: trabeculectomy (30 eyes), MDS (27 eyes), phacotrabeculectomy (28 eyes), and phaco-MDS (20 eyes). The MDS technique involved removal of a third scleral flap to expose the suprachoroidal space and excision of a trabecular block. A two-site approach was used for combined surgeries. Main outcome measures included intraocular pressure (IOP), number of glaucoma medications, and complications. Treatment success was defined as an IOP of 6–15 mmHg and/or a 30% reduction in IOP.

Results:

All groups showed significant decrease in IOP and number of medications (both P s < 0.001). The MDS group had a higher IOP (13.9 ± 3.8 vs. 12.4 ± 2.5 mmHg, P = 0.080) and required more medications (P = 0.001) than the trabeculectomy group at 1 year. The MDS group had a higher baseline IOP than the trabeculectomy group (P = 0.004) and both the groups showed similar IOP reductions (33.3% vs. 25.7%, P = 0.391). The phaco-MDS and phacotrabeculectomy groups had comparable IOP (13.3 ± 3.1 vs. 12.4 ± 3.1 mmHg, P = 0.354), number of medications (P = 0.594), and IOP reduction (P = 0.509) at 1-year follow-up visit. The trabeculectomy and phacotrabeculectomy groups developed more wound leaks (P = 0.043) and required more bleb needling during the early postoperative period (P < 0.001).

Conclusion:

The MDS technique seems to be slightly inferior to trabeculectomy, but when combined with phacoemulsification, is safer and results in similar IOP outcomes.

A retrospective analysis of the use of loteprednol etabonate ophthalmic suspension 0.5% following canaloplasty

Background

While loteprednol etabonate (LE) suspension 0.5% is approved for the treatment of postoperative ocular inflammation, there have been no reported studies of its use in glaucoma patients undergoing canaloplasty.

Methods

This was a retrospective medical chart review conducted at a single US center. Data were collected on patients with glaucoma who underwent canaloplasty with or without cataract surgery, and were prescribed LE suspension 0.5% postoperatively. Outcomes evaluated included postsurgical inflammation (anterior chamber [AC] cells and flare), intraocular pressure (IOP), number of IOP-lowering medications, and postsurgical complications.

Results

Data were collected on 204 patients (262 eyes) with a mean (SD) age of 71.6 (11.3) years. The most frequent LE dosing regimens at day 1, week 1, and month 1 postsurgery were QID (92.3%; 241/261), TID (52.6%; 133/253), and QD (65.5%; 78/119), respectively. Inflammation (AC flare and cells), mostly mild, was noted in 33.2% (86/259) of eyes on postoperative day 1 and 8.6% (21/244) of eyes at month 1. Mean IOP and mean number of IOP-lowering medications were significantly reduced from baseline (P<0.001) at all time points postoperatively. Complete (no IOP-lowering medication) or qualified (use of ≤2 IOP-lowering medications) surgical success was achieved in 78.8% and 90.6% of eyes, respectively, at month 6 and 63.4% and 92.7% of eyes at month 36. The most frequently observed postoperative complication was hyphema in 48.7% (126/259) eyes at day 1, which decreased to 0.4% (1/244) of eyes by month 1. IOP ≥30 mmHg was noted in 13 (5.3%) eyes at postoperative week 1 and rarely thereafter, and no patient discontinued therapy because of an IOP increase.

Conclusion

These real-world data suggest that canaloplasty with or without cataract surgery managed postoperatively with LE suspension 0.5% is effective and safe in the glaucoma patient.

Experimental circumferential canaloplasty with a new Schlemm canal microcatheter

AIM

To present a new, simple, inexpensive Schlemm canal microcatheter for circumferential canaloplasty in a rabbit model.

METHODS

A rabbit glaucoma animal model was established by intravitreal injection of triamcinolone acetonide. Circumferential canaloplasty with a new Schlemm canal microcatheter (patent license number: 201220029850.0) was performed. The Schlemm canal microcatheter was composed of microcatheter wall and lumen. The wall was made of high refractive index plastic optical fiber that could be attached to an illuminant so that the whole lighted microcatheter was visible during circumferential canaloplasty. The lumen could be attached to an injector for injection of viscoelastic during catheterization. Rabbits were divided randomly into the control, model and treatment groups. Intraocular pressure (IOP) was measured with a Tono-pen tonometer pre-operation and 3, 7, 14, 21 and 28d post-operation. Ultrasound biomicroscopy was performed to visualize the Schlemm canal microcatheter in the Schlemm canal and the sclera pool.

RESULTS

The Schlemm canal microcatheter could be used to perform circumferential canaloplasty in the rabbit glaucoma animal model. IOP was lower in the treatment group than that in the model group 3, 7, 14 and 28d after operation. There were no significant differences in IOP between the control group and treatment group. The differences among the three groups were statistically significant (3d: F=41.985, P<0.001; 7d: F=65.696, P<0.001; 14d: F=114.599, P<0.001; 28d: F=55.006, P<0.001).

CONCLUSION

Circumferential canaloplasty is safe and effective in control of experimental glaucoma model in rabbits.

Combined phacocanaloplasty for open-angle glaucoma and cataract: 12 months results

Purpose of the study

To evaluate efficacy, safety, and success rates of canaloplasty combined with phacoemulsification and intraocular lens implantation in patients with open-angle glaucoma (OAG) and visually significant cataract.

Patients and methods

A prospective interventional noncomparative case series carried out in Minia University Hospital from April 2015 to October 2016 on 20 eyes of 18 patients who had visually significant cataract and primary OAG. All the cases had combined phacocanaloplasty. Preoperative best-corrected visual acuity, intraocular pressure (IOP), and number of antiglaucoma medications were collected and compared to postoperative levels, and complications rates were recorded.

Results

20 eyes of 18 patients (5 males and 15 females), with a mean age 57.6 years (range 48–69 years), underwent phacocanaloplasty. Preoperative mean IOP was 25.20 ±1.009 mmHg. Postoperative IOP decreased to a mean of 14.20±0.9, 14.85±0.8, and 15.85±0.7 mmHG at 3, 6, and 12 months, respectively, with 37% reduction from preoperative IOP level at one year follow-up visit (P=0.0005). The number of antiglaucoma medications dropped from mean of 1.55 preoperatively to 0.35 postoperatively. LogMAR of best-corrected visual acuity improved from 0.6950±0.07 preoperatively to 0.3670±0.056, 0.3460±0.056, and 0.03370±0.052 at 3, 6, and 12 months postoperatively (P=0.0005). Complications were limited to mild hyphemia (one case), mild corneal edema (one case), and mild inflammatory membrane (one case) that resolved in the first week after surgery.

Conclusion

Canaloplasty combined with clear corneal phacoemulsification and intraocular lens implantation may be a safe and effective procedure to lower IOP in adult patients with OAG and visually significant cataract.

Canaloplasty versus Viscocanalostomy in Primary Open Angle Glaucoma

INTRODUCTION

The purpose of this study was to compare the efficacy and safety of canaloplasty versus viscocanalostomy in management of uncontrolled primary open angle glaucoma (POAG) with medication.

METHODS

Canaloplasty surgery was applied for thirty eyes of thirty patients (45-55 years) with a mean age of 48 years (Group A) and viscocanalostomy surgery was applied also for thirty eyes of thirty patients (43-54 years) with a mean age of 46 years (group B). All patients were with uncontrolled primary open angle glaucoma by maximally tolerated medical therapy.

RESULTS

Intraocular pressure (IOP) in both surgeries was significantly reduced through follow up period (p < 0.0.001). Complete success was 86.6% in group A and 80% in group B. Visual field deterioration was in 2 cases (6%) in group A and in 4 cases (13%) in group B. Low incidence of postoperative complications was reported as Descemet's membrane detachment (3% in group A and 8% in group B), ocular hypotony (2% in group A and 4% in group B) and hyphema (3% in group A and 5% in group B).

CONCLUSION

Canaloplasty was more effective and safer than viscocanalostomy in management of uncontrolled primary open angle glaucoma (POAG) with medication.

Intraindividual comparison of Canaloplasty versus trabeculectomy with mitomycin C in a single-surgeon series

PURPOSE

To compare the safety, efficacy, and postoperative management of canaloplasty in one eye versus trabeculectomy with mitomycin C in the contralateral eye in patients with open-angle glaucoma.

METHODS

This study was a consecutive case series of 30 eyes of 15 patients who had prior trabeculectomy with mitomycin C (group II) and later were treated with canaloplasty (group I) in the fellow eye. Primary outcome measures included intraocular pressure (IOP) and glaucoma medication after 6- and 12-month follow-up. Secondary outcome measures were number of postoperative interventions, hospitalization, and follow-up visits.

RESULTS

Mean preoperative IOP±SD was 26.73±6.4 mm Hg in group I and 26.3±10.9 mm Hg in group II (P=0.9), which decreased to 13.21±2.83 mm Hg for canaloplasty (P<0.0001) and 11.64±5.2 mm Hg for trabeculectomy (P<0.0005) including 3 patients with hypotony at 12 months. Glaucoma medication decreased from 2.5 in group I and 2.7 in group II to no medication in group I and 0.36±0.74 supplemental medication in group II 12 months postoperatively (P<0.0001). Best corrected visual acuity (±SD) was logMAR 0.06±0.09 (group I) and 0.28±0.56 (group II) before and logMAR 0.07±0.09 (group I) and 0.31±0.58 (group II) after surgery. In group I, 2 interventions were necessary. In group II, 8 eyes needed 112 interventions for filtering bleb management. Although canaloplasty took significantly longer to perform, trabeculectomy group required a longer initial postoperative hospitalization (mean 10.4 vs. 5.4 d, P<0.0001) and more postoperative follow-up visits (mean 3.9 vs. 8.5, P<0.001).

CONCLUSIONS

Canaloplasty and trabeculectomy were both effective in lowering IOP. However, less follow-up visits and significantly fewer complications and interventions were favorable for canaloplasty.

A Potential Application of Canaloplasty in Glaucoma Gene Therapy

Canaloplasty, a recently developed non-penetrating glaucoma surgical approach, may restore physiological outflow routes in primary open-angle glaucoma with less risk of severe postoperative complications than trabeculectomy. Since the inner wall of Schlemm's canal (SC) is directly in contact with the trabecular meshwork (TM) for 360 degrees and the catheter device used in canaloplasty allows viscoelastic to be injected into the entire length of SC, canaloplasty might also be used to perform SC/TM-targeted delivery of transgene vectors for glaucoma gene therapy. This hypothesized new method for transgene delivery may give the transgene access to the entire inner wall of SC and the whole juxtacanalicular region of the TM and allow the transgene to be expressed in both the TM and SC without affecting the cornea, iris and ciliary body. Further, this strategy might have a greater trabecular outflow resistance-decreasing effect than either the genetic or surgical approach alone.

A review of canaloplasty

Canaloplasty is a method of lowering intraocular pressure (IOP) by which a flexible, beacon-tipped microcatheter equipped with an ophthalmic viscosurgical device (OVD) delivery system is used to catheterize and introduce a suture into Schlemm's canal. Ligation of this suture provides tension on the canal and facilitates aqueous outflow. Canaloplasty is designed to be a blebless procedure that requires no antifibrotic agents and has been shown to safely and effectively lower IOP in patients with open-angle glaucoma (OAG) with minimal complications. Most importantly, no bleb-related adverse events are associated with this procedure. When contemplating surgical management of OAG, canaloplasty may be considered.

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.