Short-Term Intraocular Pressure Elevations after Combined Phacoemulsification and Implantation of Two Trabecular Micro-Bypass Stents: Prednisolone versus Loteprednol

Objective. To compare the effects of prednisolone and of loteprednol after combined phacoemulsification and trabecular micro-bypass stent implantation (phaco-iStent). Methods. Patients who underwent phaco-iStent between April 2013 and November 2014 were identified by retrospective chart review. Postoperatively, they received either prednisolone (n = 38) or loteprednol (n = 58). Baseline data was compared. Primary outcomes including intraocular pressure (IOP) and number of glaucoma medications (NGM) were analyzed at preoperative visit, postoperative day 1, weeks 1-2, weeks 3-4, and months 2-3. Results. Both groups had similar preoperative parameters (p > 0.05). The mean IOP spike occurred at postoperative weeks 1-2 with an increase of 2.21 ± 7.30 mmHg in the loteprednol group and 2.54 ± 9.28 mmHg in the prednisolone group. It decreased by weeks 3-4 in both groups and continued to improve at months 2-3. NGM showed significant reduction (p < 0.0001) after the surgery and remained stable in both groups. No significant group effect or time-group interaction in IOP and NGM evolution was detected (p > 0.05). The proportions of patients needing paracentesis were similar between the two groups. Conclusion. Similar early IOP elevations after combined phaco-iStent occurred with both prednisolone and loteprednol. Facilitated glucocorticoid infusion, altered aqueous humor outflow, and local inflammation may be contributing factors.

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.

Use of Various Glaucoma Surgeries and Procedures in Medicare Beneficiaries from 1994 to 2012

PURPOSE

Determine how procedural treatments for glaucoma have changed between 1994-2012.

DESIGN

Retrospective, observational analysis.

PARTICIPANTS

Medicare Part B beneficiaries.

METHODS

We analyzed Medicare fee-for-service paid claims data between 1994-2012 to determine the number of surgical/laser procedures performed for glaucoma in the Medicare population each year.

MAIN OUTCOME MEASURES

Number of glaucoma-related procedures performed.

RESULTS

Trabeculectomies in eyes without previous scarring decreased 52% from 54 224 in 1994 to 25 758 in 2003, and a further 52% to 12 279 in 2012. Trabeculectomies in eyes with scarring ranged from 9054 to 13 604 between 1994-2003, but then decreased 48% from 11 018 to 5728 between 2003-2012. Mini-shunts done via an external approach (including ExPRESS [Alcon Inc, Fort Worth, TX]) increased 116% from 2718 in 2009 to 5870 in 2012. The number of aqueous shunts to the extraocular reservoir increased 231% from 2356 in 1994 to 7788 in 2003, and a further 54% to 12 021 in 2012. Total cyclophotocoagulation procedures increased 253% from 2582 in 1994 to 9106 in 2003, and a further 54% to 13 996 in 2012. Transscleral cyclophotocoagulations decreased 45% from 5978 to 3268 between 2005-2012; over the same period, the number of endoscopic cyclophotocoagulations (ECPs) increased 99% from 5383 to 10 728. From 2001 to 2005, the number of trabeculoplasties more than doubled from 75 647 in 2001 to 176 476 in 2005, but since 2005 the number of trabeculoplasties decreased 19% to 142 682 in 2012. The number of laser iridotomies was fairly consistent between 1994-2012, increasing 9% over this period and ranging from 63 773 to 85 426. Canaloplasties increased 1407% from 161 in 2007 to 2426 in 2012. Between 1994-2012, despite a 9% increase in beneficiaries, the total number of glaucoma procedures and the number of glaucoma procedures other than laser procedures decreased 16% and 31%, respectively.

CONCLUSIONS

Despite the increase in beneficiaries, the number of glaucoma procedures performed decreased. Glaucoma procedures demonstrating a significant increase in use include canaloplasty, mini-shunts (external approach), aqueous shunt to extraocular reservoir, and ECP. Trabeculectomy use continued its long-term downward trend. The continued movement away from trabeculectomy and toward alternative intraocular pressure-lowering procedures highlights the need for well-designed clinical trials comparing these procedures.

Surgery on the Trabecular Meshwork: Histopathological Evidence

Juxtacanalicular (JXT) trabecular meshwork and endothelial lining of Schlemm's canal have been cited as the loci of aqueous outflow resistance, both in a normal as well as a glaucomatous eye. In this review, we attempt to understand the currently available surgical modalities in light of the available histopathological evidence, regarding localization of outflow resistance. How to cite this article: Bhartiya S, Ichhpujani P, Shaarawy T. Surgery on the Trabecular Meshwork: Histopathological Evidence. J Curr Glaucoma Pract 2015;9(2):51-61.

A review of the iStent(®) trabecular micro-bypass stent: safety and efficacy

There is a significant demand for procedures that can effectively treat glaucoma with low risk and good visual outcomes. To fill this void, procedures termed “minimally invasive glaucoma surgery”, are gaining in popularity. This review will focus on the safety and efficacy of one such minimally invasive glaucoma surgery procedure, the trabecular micro-bypass stent. This stent is intended to lower intraocular pressure by directly cannulating Schlemm’s canal and thereby enhancing aqueous outflow. Recent randomized controlled trials and case series have demonstrated the micro-bypass stent to be a relatively safe procedure, with limited complications and no serious adverse sequelae. The most common complication across all studies was stent obstruction or malposition, which generally did not result in any adverse outcome in vision or pressure control. In addition, increased rates of hypotony, choroidal hemorrhage, or infection were not seen with the micro-bypass stent in comparison to cataract surgery alone.

Prospective evaluation of microinvasive glaucoma surgery with trabecular microbypass stents and prostaglandin in open-angle glaucoma

PURPOSE

To evaluate the intraocular pressure (IOP) lowering effect of 2 trabecular microbypass stents and postoperative travoprost in patients with open-angle glaucoma (OAG) not controlled on 2 medications preoperatively.

SETTING

S.V. Malayan Ophthalmology Centre, Yerevan, Armenia.

DESIGN

Prospective open-label nonrandomized study.

METHODS

This prospective pilot study involved 39 qualified phakic patients with OAG, medicated IOP between 18 mm Hg and 30 mm Hg, and unmedicated baseline (after washout) IOP between 22 mm Hg and 38 mm Hg. Patients received 2 stents (iStent) through a clear corneal incision and were prescribed travoprost starting the night of postoperative day 1. Intraocular pressure, complications, and various safety measures were assessed at examinations through 18 months and planned for every 6 months thereafter until month 60. A washout of medications was performed 13 months postoperatively.

RESULTS

All patients achieved an IOP reduction of 20% or more from baseline to 12 months with reduction of 1 medication and with IOP 18 mm Hg or less. Follow-up through 18 months showed that medicated IOP decreased from 22.2 mm Hg ± 2.0 (SD) on 2 medications preoperatively to 14 mm Hg or less on 1 medication at the postoperative visits. The mean unmedicated IOP decreased from 25.3 ± 1.8 mm Hg preoperatively to 17.1 ± 2.2 mm Hg 13 months postoperatively. No intraoperative or serious device-related adverse events occurred.

CONCLUSIONS

Patients with OAG treated with 2 trabecular microbypass stents and 1 presumptive postoperative medication achieved a significant and sustained reduction in IOP and medication through 18 months.

FINANCIAL DISCLOSURE

Dr. Katz served as the medical monitor for this study. All authors are consultants to Glaukos Corp.

iStent trabecular micro-bypass stent for open-angle glaucoma

Trabecular micro-bypass stents, commonly known as iStents, are micro-invasive glaucoma surgery (MIGS) devices used to treat open-angle glaucoma. Like other MIGS procedures that enhance trabecular outflow, the iStent lowers intraocular pressure (IOP) by creating a direct channel between the anterior chamber and Schlemm’s canal. iStents are typically implanted at the time of phacoemulsification for patients with open-angle glaucoma and visually significant cataracts. This review summarizes the published data regarding the efficacy, safety, and cost considerations of trabecular micro-bypass stents. Most studies found statistically significant reductions in mean IOP and ocular medication use after combined phacoemulsification with single or double iStent implantation. The devices were found to be very safe, with a safety profile similar to that of cataract surgery. Complications were infrequent, with the most common complications being temporary stent obstruction or malposition, which resolved with observation or secondary procedures. Future studies are needed to evaluate long-term outcomes, patient satisfaction, cost effectiveness, and expanded indications.

Prospective unmasked randomized evaluation of the iStent inject (®) versus two ocular hypotensive agents in patients with primary open-angle glaucoma

PURPOSE

The purpose of this study was to compare outcomes of subjects with open-angle glaucoma (OAG) not controlled on one medication who underwent either implantation of two iStent inject (®) trabecular micro-bypass devices or received medical therapy consisting of a fixed combination of latanoprost/timolol.

PATIENTS AND METHODS

Of 192 subjects who qualified for the study and were enrolled, 94 were randomized to surgery with implantation of two iStent inject(®) devices in the treated eye and 98 to receive medical therapy.

RESULTS

At the month 12 visit, 94.7% of eyes (89/94) in the stent group reported an unmedicated intraocular pressure (IOP) reduction of ≥20% versus baseline unmedicated IOP, and 91.8% of eyes (88/98) in the medical therapy group reported an IOP reduction ≥20% versus baseline unmedicated IOP. A 17.5% between-group treatment difference in favor of the iStent inject group was statistically significant (P=0.02) at the ≥50% level of IOP reduction. An IOP ≤18 mmHg was reported in 92.6% of eyes (87/94) in the iStent inject group and 89.8% of eyes (88/98) in the medical therapy group. Mean (standard deviation) IOP decreases from screening of 8.1 (2.6) mmHg and 7.3 (2.2) mmHg were reported in the iStent inject and medical therapy groups, respectively. A high safety profile was also noted in this study in both the iStent inject and medical therapy groups, as measured by stable best corrected visual acuity, cup-to-disc ratio, and adverse events.

CONCLUSION

These data show that the use of iStent inject is at least as effective as two medications, with the clinical benefit of reducing medication burden and assuring continuous treatment with full compliance to implant therapy as well as having a highly favorable safety profile.

New options for combined cataract and glaucoma surgery

PURPOSE OF REVIEW

To review the current literature regarding the effectiveness and risks of new surgeries that can be combined with phacoemulsification in the management of cataract and glaucoma.

RECENT FINDINGS

Surgical options for concurrently managing cataract and glaucoma have expanded in recent years. Endoscopic cyclophotocoagulation, trabecular micro-bypass stent, ab interno trabeculectomy, and canaloplasty may be performed in conjunction with cataract extraction to provide additional intraocular pressure (IOP) reduction. Studies evaluating these new glaucoma procedures combined with phacoemulsification generally include retrospective case series without a comparison group. Because cataract surgery alone is associated with IOP reduction, the relative contribution of the glaucoma procedure in lowering IOP cannot be determined in these studies. Randomized clinical trials are needed to better evaluate the efficacy and safety of newer glaucoma procedures in combination with cataract surgery.

SUMMARY

The newer glaucoma procedures appear less effective than trabeculectomy, but they are associated with a lower risk of surgical complications.

Characterization of micro-invasive trabecular bypass stents by ex vivo perfusion and computational flow modeling

Micro-invasive glaucoma surgery with the Glaukos iStent® or iStent inject® (Glaukos Corporation, Laguna Hills, CA, USA) is intended to create a bypass through the trabecular meshwork to Schlemm’s canal to improve aqueous outflow through the natural physiologic pathway. While the iStent devices have been evaluated in ex vivo anterior segment models, they have not previously been evaluated in whole eye perfusion models nor characterized by computational fluid dynamics. Intraocular pressure (IOP) reduction with the iStent was evaluated in an ex vivo whole human eye perfusion model. Numerical modeling, including computational fluid dynamics, was used to evaluate the flow through the stents over physiologically relevant boundary conditions. In the ex vivo model, a single iStent reduced IOP by 6.0 mmHg from baseline, and addition of a second iStent further lowered IOP by 2.9 mmHg, for a total IOP reduction of 8.9 mmHg. Computational modeling showed that simulated flow through the iStent or iStent inject is smooth and laminar at physiological flow rates. Each stent was computed to have a negligible flow resistance consistent with an expected significant decrease in IOP. The present perfusion results agree with prior clinical and laboratory studies to show that both iStent and iStent inject therapies are potentially titratable, providing clinicians with the opportunity to achieve lower target IOPs by implanting additional stents.

Prospective, unmasked evaluation of the iStent® inject system for open-angle glaucoma: synergy trial

Introduction

Micro-invasive glaucoma surgical implantation of trabecular micro-bypass stents, previously shown to be safe and effective for open-angle glaucoma (OAG) subjects during cataract surgery, was considered for evaluation as a sole procedure. The aim of this study was to evaluate the safety and intraocular pressure (IOP)-lowering efficacy after ab interno implantation of two Glaukos Trabecular Micro-Bypass iStent inject second generation devices in subjects with OAG. This study was performed at sites in France, Germany, Italy, Republic of Armenia, and Spain.

Methods

In this pan-European, multi-center prospective, post-market, unmasked study, 99 patients with OAG on at least two topical ocular hypotensive medications who required additional IOP lowering to control glaucoma disease underwent implantation of two GTS400 stents in a stand-alone procedure. Patients were qualified if they presented with preoperative mean IOP between 22 and 38 mmHg after medication washout. Postoperatively, subjects were assessed at Day 1, Months 1, 3, 6, 7, 9, and 12. IOP, medication use and safety were assessed at each visit.

Results

Sixty-six percent of subjects achieved IOP ≤18 mmHg at 12 months without medication, and 81% of subjects achieved Month 12 IOP ≤ 18 mmHg with either a single medication or no medication. Mean baseline washout IOP values decreased by 10.2 mmHg or 39.7% from 26.3 (SD 3.5) mmHg to 15.7 (SD 3.7) mmHg at Month 12. Mean IOP at 12 months was 14.7 (SD 3.1) mmHg in subjects not using ocular hypotensive medications. Reduction from preoperative medication burden was achieved in 86.9% of patients, including 15.2% with reduction of one medication and 71.7% with reduction of two or more medications. Postoperative complications occurred at a low rate and resolved without persistent effects.

Conclusion

In this series, implantation of two trabecular micro-bypass second generation stents in subjects with OAG resulted in IOP and medication reduction and favorable safety outcomes.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-014-0095-y) contains supplementary material, which is available to authorized users.

Update on Minimally Invasive Glaucoma Surgery (MIGS) and New Implants

Traditional glaucoma surgery has been challenged by the advent of innovative techniques and new implants in the past few years. There is an increasing demand for safer glaucoma surgery offering patients a timely surgical solution in reducing intraocular pressure (IOP) and improving their quality of life. The new procedures and devices aim to lower IOP with a higher safety profile than fistulating surgery (trabeculectomy/drainage tubes) and are collectively termed “minimally invasive glaucoma surgery (MIGS).” The main advantage of MIGS is that they are nonpenetrating and/or bleb-independent procedures, thus avoiding the major complications of fistulating surgery related to blebs and hypotony. In this review, the clinical results of the latest techniques and devices are presented by their approach, ab interno (trabeculotomy, excimer laser trabeculotomy, trabecular microbypass, suprachoroidal shunt, and intracanalicular scaffold) and ab externo (canaloplasty, Stegmann Canal Expander, suprachoroidal Gold microshunt). The drawback of MIGS is that some of these procedures produce a limited IOP reduction compared to trabeculectomy. Currently, MIGS is performed in glaucoma patients with early to moderate disease and preferably in combination with cataract surgery.

Mid-term evaluation of the new Glaukos iStent with phacoemulsification in coexistent open-angle glaucoma or ocular hypertension and cataract

AIMS

To evaluate the mid-term efficacy and safety of the GTS-400-iStent combined with phacoemulsification in patients with cataract and open-angle glaucoma (OAG) or ocular hypertension (OHT).

METHODS

Prospective, non-comparative, uncontrolled, interventional case series study. Subjects underwent phacoemulsification and two GTS-400 implantation. Efficacy outcomes: intraocular pressure (IOP) and antiglaucoma medications. Safety outcomes: complications, best-corrected visual acuity and endothelial cell count (ECC). Follow-up was 1 year.

RESULTS

20 patients were enrolled (mean age: 75.1 ± 8.6 years). Mean medicated baseline IOP was 19.95 ± 3.71 mm Hg and 26 ± 3.11 mm Hg without medication. Mean final IOP was 16.75 ± 2.24, determining a final IOP decrease of 35.68% (9.42 ± 3 mm Hg; p<0.001), from baseline washout IOP. Mean number of medications fell from 1.3 ± 0.66 to 0.3 ± 0.57 (P<0.001). 75% of patients were off medications at one year. Mean ECC decreased from 2289.64 ± 393.5 cells/mm(2) to 1986.95 ± 520.58 cells/mm(2).

CONCLUSIONS

Combined cataract surgery with implantation of GTS-400-iStent seems to be an effective and safe procedure.

[Minimally invasive iridocorneal angle surgery]

The classical filtration surgery with trabeculectomy or drainage of chamber fluid with episcleral implants is the most effective method for permanent reduction of intraocular pressure to lower and normal levels. Even though both operative procedures are well-established the high efficiency of the method causes potentially dangerous intraoperative as well as interoperative complications with a frequency which cannot be ignored. In the past this led to a search for low complication alternatives with non-penetrating glaucoma surgery (NPGS) and the search is still continuing. Trabecular meshwork surgery in particular with continuous development of new operation techniques steered the focus to a complication-poor and minimally invasive, gonioscopic glaucoma surgery.

Using multiple trabecular micro-bypass stents in cataract patients to treat open-angle glaucoma

PURPOSE

To evaluate the efficacy of multiple trabecular micro-bypass stents combined with cataract surgery in patients with open-angle glaucoma (OAG) and cataract.

SETTING

Private practice, Mississauga, Ontario, Canada.

DESIGN

Comparative case series.

METHODS

Eyes with OAG had implantation of 2 or 3 micro-bypass stents with concurrent cataract surgery and follow-up through 1 year. Efficacy measures were intraocular pressure (IOP) and topical ocular hypotensive medication use. Safety assessment included complications and corrected distance visual acuity (CDVA).

RESULTS

The study comprised 53 eyes (47 patients); 28 had implantation of 2 stents and 25 had implantation of 3 stents. The overall mean 1-year postoperative IOP was 14.3 mm Hg, which was significantly lower than preoperative IOP overall and in each group (P<.001). The target IOP was achieved in a significantly higher proportion of eyes at 1 year versus preoperatively (77% versus 43%; P<.001). Overall, 83% of eyes had a decrease in topical ocular hypotensive medication at 1 year from preoperatively, with a 74% decrease in the mean number of medications (from 2.7 to 0.7) at 1 year (P<.001). The 3-stent group was on significantly fewer medications than the 2-stent group at 1 year (0.4 versus 1.0; P=.04).

CONCLUSIONS

Using multiple micro-bypass stents with concurrent cataract surgery led to a mean postoperative IOP of less than 15 mm Hg and allowed patients to achieve target pressure control with significantly fewer medications through 1 year.

FINANCIAL DISCLOSURE

Dr. Ahmed is a consultant to Glaukos Corp. No other author has a financial or proprietary interest in any material or method mentioned.

Second-generation trabecular meshwork bypass stent (iStent inject) increases outflow facility in cultured human anterior segments

PURPOSE

To determine whether a second-generation trabecular meshwork (TM) bypass stent (iStent inject) influences outflow facility in cultured human anterior segments.

DESIGN

Prospective laboratory investigation using normal human donor eyes.

METHODS

Human anterior segments (n = 7) were placed in perfusion organ culture. One or 2 iStent inject stents were inserted into the TM within the nasal and/or superior quadrants using a specially designed injector. Anterior segments were returned to culture and perfused for an additional 24 hours. Morphology of the TM and Schlemm canal (SC) was assessed by scanning electron microscopy (SEM) and 3-dimensional micro-computed tomography (3D micro-CT).

RESULTS

Insertion of 1 iStent inject into the nasal or superior quadrant of the TM increased outflow facility from 0.16 ± 0.05 μL/min/mm Hg to 0.38 ± 0.23 μL/min/mm Hg (P < .03, n = 7), with concurrent pressure reduction from 16.7 ± 5.4 mm Hg to 8.6 ± 4.4 mm Hg. Addition of a second iStent inject further increased outflow facility to 0.78 ± 0.66 μL/min/mm Hg (n = 2). SEM showed the iStent inject flange compressed against the uveal region of the TM, the thorax securely inserted within the TM, and the head located in the lumen of SC. Dilation of SC was noted around the iStent inject head and SC cell disruption was observed at the iStent inject insertion site. 3D micro-CT confirmed iStent inject placement.

CONCLUSION

iStent inject, a second-generation bypass stent, increased outflow facility in human anterior segment culture. The iStent inject is a promising new device to lower intraocular pressure via TM bypass.

Clinical options for the reduction of elevated intraocular pressure

Elevated IOP in clinical practice is usually seen in glaucoma or ocular hypertension. Glaucoma affects 60 million people worldwide and 8.4 million are bilaterally blind from this chronic disease.1 Options for reducing IOP rely on pharmacological agents, laser treatments and surgery which may be penetrating or non-penetrating. The last twenty years has seen significant changes in all of these strategies. This review aims to cover these clinical options and introduce some of the new technologies currently in development for the clinical lowering of IOP.

Glaukos® Trabecular Stent used to Treat Steroid-Induced Glaucoma

Purpose

This case report illustrates the efficacy of the Glaukos trabecular bypass (Glaukos i-stent, Glaukos Corporation, Laguna Hills, California, USA) used for intraocular pressure (IOP) control in a patient with glaucoma induced by the steroid treatment of post–laser-assisted in situ keratomileusis (LASIK) bilateral anterior uveitis.

Methods

A 35-year-old woman who had undergone LASIK 5 months previously presented with blurred vision in both eyes. Examination revealed bilateral anterior uveitis and diffuse lamellar keratitis (DLK) requiring steroid treatment. In response to treatment, inflammation improved but the patient had increased IOP that was difficult to control. The course of pressure elevation was more aggressive in the left eye despite the gradual discontinuation of steroids. We therefore decided to place 2 trabecular i-stents in the left eye.

Results

This solution achieved good pressure control with no associated complications after 1 year follow-up.

Conclusions

This trabecular bypass seems a safe and effective therapeutic option for IOP control when there is a poor response to conventional treatment in this type of secondary glaucoma.

Novel glaucoma procedures: a report by the American Academy of Ophthalmology

OBJECTIVE

To review the published literature and summarize clinically relevant information about novel, or emerging, surgical techniques for the treatment of open-angle glaucoma and to describe the devices and procedures in proper context of the appropriate patient population, theoretic effects, advantages, and disadvantages.

DESIGN

Devices and procedures that have US Food and Drug Administration clearance or are currently in phase III clinical trials in the United States are included: the Fugo blade (Medisurg Ltd., Norristown, PA), Ex-PRESS mini glaucoma shunt (Alcon, Inc., Hunenberg, Switzerland), SOLX Gold Shunt (SOLX Ltd., Boston, MA), excimer laser trabeculotomy (AIDA, Glautec AG, Nurnberg, Germany), canaloplasty (iScience Interventional Corp., Menlo Park, CA), trabeculotomy by internal approach (Trabectome, NeoMedix, Inc., Tustin, CA), and trabecular micro-bypass stent (iStent, Glaukos Corporation, Laguna Hills, CA).

METHODS

Literature searches of the PubMed and the Cochrane Library databases were conducted up to October 2009 with no date or language restrictions.

MAIN OUTCOME MEASURES

These searches retrieved 192 citations, of which 23 were deemed topically relevant and rated for quality of evidence by the panel methodologist. All studies but one, which was rated as level II evidence, were rated as level III evidence.

RESULTS

All of the devices studied showed a statistically significant reduction in intraocular pressure and, in some cases, glaucoma medication use. The success and failure definitions varied among studies, as did the calculated rates. Various types and rates of complications were reported depending on the surgical technique. On the basis of the review of the literature and mechanism of action, the authors also summarized theoretic advantages and disadvantages of each surgery.

CONCLUSIONS

The novel glaucoma surgeries studied all show some promise as alternative treatments to lower intraocular pressure in the treatment of open-angle glaucoma. It is not possible to conclude whether these novel procedures are superior, equal to, or inferior to surgery such as trabeculectomy or to one another. The studies provide the basis for future comparative or randomized trials of existing glaucoma surgical techniques and other novel procedures.

Glaukos iStent Trabecular Micro-Bypass

The iStent trabecular micro-bypass system (Glaukos Corp. Laguna Hills, CA) was developed to address the limitations of current medical and surgical therapies for glaucoma treatment. The iStent^® is inserted ab interno through a small temporal clear corneal incision, bypassing the trabecular meshwork and placed in Schlemm's canal at the lower nasal quadrant. Implantation of this stent into Schlemm's canal allows aqueous humor to drain directly from the anterior chamber into Schlemm's canal bypassing the obstructed trabecular meshwork. For this review, a Medline search was performed using the terms “trabecular micro-bypass stent” and “trabecular bypass stent.” The online abstract database for the American Academy of Ophthalmology was also reviewed. Abstracts which duplicated published articles were excluded. All relevant papers (n is equal to three) and abstracts (n is equal to one) were included in this review. Multiple, prospective multi-country, clinical trials have demonstrated the safety and efficacy of iStent in reducing IOP, when compared to traditional treatment modalities, while reducing/ eliminating the need for ocular antihypertensive drugs when implanted in OAG patients during combined cataract surgery or in patients with glaucoma refractory to traditional treatment modalities.