Minimally Invasive Glaucoma Surgery: Latest Developments and Future Challenges.

The development of minimally invasive glaucoma surgeries (MIGSs) was intended to provide safe and modestly efficacious modalities for early intervention of mild-to-moderate glaucoma, with minimal trauma and rapid recovery. They were mainly ab interno procedures that reduce intraocular pressure by facilitating the aqueous outflow by bypassing the trabecular meshwork resistance, reinforcing the uveoscleral flow via the supraciliary space, and reducing aqueous production by the ciliary body. While the cumulating evidence helps shape the role of the available MIGS, the exponential new development and advancement in this field has expanded the territory of MIGS. Apart from developing subconjunctival MIGS filtration devices (Xen gel stent and PRESERFLO MicroShunt), there is a tendency to revisit the "traditional" MIGS for alternative use and to modify the procedures with consideration of the fundamental aqueous outflow physiology. Combined MIGS has also been suggested, based on the theory that their different mechanisms may provide additive or synergistic effects. The advancement of laser procedures is also promising and could supplement unmet needs along the glaucoma treatment algorithm. This review examines the broad array of MIGS, updates the recent findings, discusses their potential alternative applications, and explores future challenges.

[Review by the French Glaucoma Society on the roles of new surgical techniques in glaucoma]. / Mise au point de la Société française du glaucome sur la place des nouvelles techniques chirurgicales dans le glaucome.

The surgical management of glaucoma has been enriched in recent years by the arrival of new surgical techniques as a group known as MIGS (minimally invasive glaucoma surgery). The objective of these new techniques is to reduce intraocular pressure (IOP) while limiting the risk of complications of conventional filtering surgery and allowing faster visual recovery. MIGS can be classified into three main categories depending on the route used to promote the outflow of aqueous humor: the trabecular route, the suprachoroidal route and the subconjunctival route. MIGS using the subconjunctival route are also called minimally invasive bleb surgery (MIBS). These new techniques do not replace conventional filtering surgery, which remains the gold standard technique, but now offer new alternatives for the surgical management of glaucoma patients in combination with cataract surgery or as stand-alone procedures.

Clinical outcomes of penetrating canaloplasty in patients with traumatic angle recession glaucoma: a prospective interventional case series.

BACKGROUND/AIM: To evaluate the clinical outcomes of penetrating canaloplasty in traumatic angle recession glaucoma at 1 year. METHODS: Patients with angle recession glaucoma underwent penetrating canaloplasty, a new Schlemm's canal-based internal drainage procedure, which creates a direct canal for flow of aqueous humour from the anterior chamber to the ostia of Schlemm's canal via a window created at the corneal scleral bed without use of antimetabolites. Postoperative intraocular pressure (IOP), number of glaucoma medications, and procedure-related complications were evaluated. Success was defined as an IOP ≤21 mm Hg without (complete) or with (qualified) use of glaucoma medication. RESULTS: Forty eyes in 40 patients with angle recession glaucoma underwent successful circumferential catheterisation. The mean patient age was 42±13 years. In patients with penetrating canaloplasty that was deemed to be completely successful, the mean IOP decreased from a preoperative value of 37.8±12.3 mm Hg on 3.3±1.2 anti-glaucoma medications to 18.5±6.4 mm Hg on 1.2±1.4 medications, 14.9±4.6 mm Hg on 0.1±0.5 medications, 15.7±5.4 mm Hg on 0.1±0.4 medications and 14.8±3.6 mm Hg on 0.1±0.5 medications at 1, 3, 6 and 12 months postoperatively (p<0.05). Complete success was achieved in 35/40 eyes (87.5%) at 6 months and in 34/38 (89.5%) at 12 months. Hyphema (18/40, 45.0%) and transient IOP elevation (≥30 mm Hg, 9/40, 22.5%) were the most common postoperative complications. CONCLUSION: Penetrating canaloplasty significantly reduces IOP and has a high success rate in angle recession glaucoma. TRIAL REGISTRATION NUMBER: ChiCTR1900020511.

Canaloplasty in the spotlight: surgical alternatives and future perspectives.

The modern glaucoma surgeon is faced with many surgical alternatives for the management of glaucoma. In recent years, numerous techniques that make Schlemm's canal (SC) more accessible for surgery by being less invasive and surgically less challenging were introduced. Since its first introduction, canaloplasty has become a well-established method of glaucoma surgery. The aim of this paper was to present an overview of canaloplasty and its modifications, and to highlight their strong points and potential drawbacks based on available data on the effectiveness of each technique. Furthermore, it offered an overview of the development of canaloplasty over time and the clinical aspects that should be considered in patient selection. Abbreviations: ABiC = Canaloplasty ab interno, AH = aqueous humour, CSD = Canaloplasty with suprachoroidal drainage, IOP = intraocular pressure, MIGS = minimally invasive glaucoma surgery, OAG = open angle glaucoma, PEXG = pseudoexfoliation glaucoma, SC = Schlemm's canal, TDM = trabeculo-Descemet's membrane.

Achieving Inner Aqueous Drain in Glaucoma Secondary to Iridocorneal Endothelial Syndrome: One Year Results of Penetrating Canaloplasty.

PURPOSES: To report the efficacy of a bleb-independent penetrating canaloplasty in the management of glaucoma secondary to iridocorneal endothelial syndrome (GS-ICE). DESIGN: Prospective, non-comparative clinical study. METHODS: Penetrating canaloplasty was performed on 35 eyes from 35 patients with GS-ICE and medically uncontrolled intraocular pressure (IOP) between January 2018 and April 2020. Patients were followed up at 1 week, months 1, 3, 6, 12 postoperatively, and semi-annually thereafter. The IOP, anti-glaucoma medication, and surgery-related complications were recorded. Surgical success was defined as IOP ≥ 5 mmHg and ≤ 21 mmHg without (complete success) or with/without (qualified success) IOP-lowering medication. RESULTS: A total of 29 eyes (82.9%) had 360° catheterization and successfully received penetrating canaloplasty. Of these eyes, 24 (82.8%) achieved qualified success and 22 (75.9%) achieved qualified success at 12 months after surgery. The mean IOP decreased from 39.5 ± 11.8 mmHg on 2.9 ± 1.0 medications before surgery to 16.6 ± 5.3 mmHg (P < .001) on 0.2 ± 0.6 medications (P < .001) at 12 months postoperatively, respectively. Hyphema (37.9%), transient hypotony (34.5%), and transient postoperative IOP elevation (≥ 30 mmHg, 17.9%) were the most commonly observed early complications at the 1 week and 1 month visits. From 1 month and beyond, all treated eyes showed no obvious bleb at the operation quadrant. CONCLUSIONS: Penetrating canaloplasty rescued the inner aqueous outflow in ICE eyes and demonstrated acceptable success in IOP control with few complications, providing a new option for the management of GS-ICE.

Canaloplasty - Efficacy and Safety in an 18-Month Follow Up Period, and Analysis of Outcomes in Primary Open Angle Glaucoma Pigmentary Glaucoma and Pseudoexfoliative Glaucoma.

PURPOSE: Open-angle glaucoma (OAG), accounting for 90% of all glaucoma cases, is a progressive optic nerve neuropathy. It may lead to irreversible loss of visual field and complete blindness. When conservative treatment becomes insufficient to stop OAG progression, a surgical intervention is considered. Currently, canaloplasty procedure is being introduced instead of conventional trabeculectomy for invasive OAG treatment. The aim of the study is to asses safety and efficacy of canaloplasty. METHODS: This prospective study included 67 eyes that received 360° canaloplasty with placement of a tensioning suture. Primary OAG (n = 35), secondary OAG in pseudoexfoliative syndrome (n = 13), and pigmentary glaucoma (n = 19) patients were included. Control check-ups were conducted pre-operatively and in a 18-month follow-up time. Study endpoints involved reduction in IOP values and in the number of glaucoma medications after the intervention. RESULTS: The intervention led to a significant 38% reduction in IOP value from the preoperative baseline to 18 months after the intervention. The number of medications decreased significantly by 89%. At 18 months postoperative, 79% eyes did not require any glaucoma medications. The incidence of complications after canaloplasty was low, and none of the adverse effects were vision threatening. A surgically-induced astigmatism was the most frequent complication. Pigmentary glaucoma patients were the most beneficial subgroup, with 50% reduction in IOP, the highest success rate, and 98% reduction in the number of medications used. CONCLUSION: This study proved that canaloplasty is an efficient and safe procedure in OAG eyes.

A modified model of glaucoma filtering surgery in Sprague-Dawley rats.

Animal models are useful in glaucoma research to study tissue response to wound healing. Smaller animals such as rats offer additional advantages in terms of availability of detection antibodies and microarrays with cheaper maintenance costs. In this study, we describe a glaucoma filtering surgery (GFS) model in adult Sprague-Dawley rats by performing a sclerostomy using a 26-G needle and additionally placing a silicone tube (27 G) connecting the anterior chamber to the subconjunctival space to maintain a patent fistula for the flow of aqueous humor, thus providing a more definitive bleb. This technique will be useful in identifying and modifying newer targets in the wound healing process in order to improve surgical outcomes following GFS.

The surgical management of glaucoma: A review.

After a long period of little change, glaucoma surgery has experienced a dramatic rise in the number of possible procedures in the last two decades. Glaucoma filtering surgeries with mitomycin C and glaucoma drainage devices remain the standard of surgical care. Other newer surgeries, some of which are minimally or microinvasive glaucoma surgeries, target existing trabecular outflow, enhance suprachoroidal outflow, create subconjunctival blebs, or reduce aqueous production. Some require the implantation of a device such as the iStent, Hydrus, Ex-PRESS, XEN and PRESERFLO, whilst others do not-Trabectome, Kahook dual blade, Ab interno canaloplasty, gonioscopy-assisted transluminal trabeculotomy, OMNI and excimer laser trabeculotomy. Others are a less destructive variation of an established procedure, such as micropulse transscleral cyclophotocoagulation, endoscopic cyclophotocoagulation and ultrasound cycloplasty. Cataract surgery alone can be a significant glaucoma operation. These older and newer glaucoma surgeries, their mechanism of action, efficacy and complications are the subject of this review.

Clinical outcomes of viscocanalostomy and phacoviscocanalostomy in primary open angle glaucoma: Two years follow-up.

PURPOSE: To compare the outcomes of phacoviscocanalostomy and viscocanalostomy in patients with primary open angle glaucoma. METHODS: This non randomized, prospective comparative study included 168 eyes of 168 patients with primary open angle glaucoma (POAG). Phacoviscocanalostomy was performed in 94 eyes with POAG and cataract and viscocanalostomy was performed in 74 eyes with POAG. Preoperative and postoperative intraocular pressures (IOP), number of antiglaucoma medication, intraoperative and postoperative complications were recorded throughout the follow-up period. RESULTS: The mean follow-up after surgery was 20.13 ± 7.9 months. Mean IOP decreased significantly 1 month after surgery in both groups (p < 0.001) and remained significantly lower from its preoperative value at all follow-up visits. The postoperative mean IOP at the last follow up in phacoviscocanalostomy and viscocanalostomy was 14.98 ± 4.8 mmHg and 16.84 ± 5.0 mmHg, respectively (p = 0.001). Complete success rate in phacoviscocanalostomy and viscocanalostomy groups was 83.1% and 56.8%, respectively (p = 0.008). Qualified success rate was achieved in 89.4% eyes in the phacoviscocanalostomy group and 83.8% of viscocanalostomy group (p = 0.534). The Best corrected visual acuity (BCVA) in phacoviscocanalostomy group improved significantly post-operatively (p = 0.001). Postoperative antiglaucoma medication in both groups were significantly less than the preoperative values (p = 0.001). CONCLUSIONS: Both Phacoviscocanalostomy and viscocanalostmy are effective procedures in the control of IOP in patients with POAG with and without cataract. Higher complete success rates and BCVA were achieved in phacoviscocanalostomy. Therefore, phacoviscocanalostomy and viscocanalostomy are recommended in eyes with medically uncontrolled primary open-angle glaucoma with and without coexisting cataract.

Improving health-related quality of life in glaucoma during 11 years and its association with vision loss and treatment of the disease.

PURPOSE: To evaluate the impact of glaucoma on health-related quality of life (HRQoL) and mental health in the ageing population of Finland. METHODS: Altogether 7380 and 5774 Finnish individuals aged 30 years and older with known eye disease status were studied in 2000 and 2011, respectively, in two population-based surveys, including an 11-year follow-up of 4683 participants. Data on HRQoL (EQ-5D-3L, 15D), depression (BDI), psychological distress (GHQ-12) and eye disease diagnoses were obtained from self-reported assessments. Information on glaucoma was complemented with the medication, diagnosis and eye surgery data obtained from the Finnish Health Registries. Distance visual acuity was assessed using the Snellen eye chart test. In logistic regression analyses, data were corrected for age, gender and the most common comorbidities. RESULTS: Glaucoma patients with verified diagnosis (n = 192 in 2000, n = 202 in 2011) and individuals with self-suspected glaucoma (n = 100 in 2000, n = 41 in 2011) showed a significant decrease in their HRQoL. Glaucoma was also associated with worsened overall mental health based on BDI and GHQ-12 results. Visual impairment associated with glaucoma is the major determinant of the reduced HRQoL and mental health. Neither glaucoma medication nor glaucoma surgery affected these parameters. The impact of glaucoma on HRQoL and mental health diminished between 2000 and 2011 in a cross-sectional setting. The newly diagnosed glaucoma during the 11-year follow-up had a minimal effect on them. CONCLUSION: Glaucoma patients show reduced HRQoL and mental health, which is associated with vision loss regardless of the awareness or treatment of the disease. However, this effect seems to be diminishing over time, and the newly diagnosed glaucoma did not show a significant effect on either HRQoL or mental health.

Anterior-segment optical coherence tomography of filtering blebs in the early postoperative period of ab externo SIBS microshunt implantation with mitomycin C: Morphological analysis and correlation with intraocular pressure reduction.

PURPOSE: To analyse the morphological evolution of filtering blebs with anterior-segment OCT (AS-OCT) and its correlation with intraocular pressure after ab externo SIBS microshunt implantation with mitomycin C (MMC) during a 3-month follow-up period. METHODS: Twenty-eight filtering blebs of 28 patients with open-angle glaucoma were measured horizontally and vertically in the sub-Tenon space with AS-OCT after ab externo SIBS microshunt implantation with MMC. The intraocular pressure (IOP) was monitored simultaneously at each visit. Maturation of and morphological changes in the blebs and correlations with the IOP were recorded. RESULTS: The average median preoperative IOP of 20.7 (range, 12-30) mmHg decreased to 8.5 (range, 4-17), 8.9 (range, 5-17), 10.4 (range, 8-16) and 10.9 (range, 9-15) mmHg at 24 hr, 1 week, 1 month and 3 months, respectively (p < 0.001). A multiform morphology on AS-OCT prevailed at all time points, with a 3.5% rate of a uniform bleb morphology at the first week. The horizontal and vertical diameters of the blebs increased from baseline to the third month. The horizontal expansion (406 ± 127 µm on day 7, p = 0.04, 712 ± 211 µm on day 30, p = 0.02 and 952 ± 218 µm on day 90, p < 0.001) was greater than the vertical expansion (16 ± 18 µm, p = 0.3 on day 1, 63 ± 27 µm, p = 0.02 on day 30 and 137 ± 34 µm, p < 0.001 on day 90) without correlation with the IOP (r = -0.3, p = 0.2). CONCLUSION: Anterior-segment OCT (AS-OCT) of the filtering blebs formed after ab externo SIBS microshunt implantation showed progressive horizontal and vertical expansion of the blebs in the sub-Tenon space, with a significant peak at the first month not significantly correlated with the decrease in the IOP.

Statin use and the reoperation rates in glaucoma filtration surgery - population-based cohort study.

PURPOSE: To examine the association of systemic statin therapy and reoperation rate after glaucoma filtration surgery (GFS). METHODS: This is a population-based, historic cohort study of 2705 eyes undergoing GFS in Finland between July 2009 and December 2016. GFSs were identified from national administrative healthcare registers. Baseline sociodemographic and health characteristics were documented. Reoperation rates of GFS subgroups were analysed, with statin users compared to non-users. The outcomes were modelled using a Poisson regression model adjusted for age, sex, education, statin use, chronic comorbidities, and cataract surgery with incident rate ratios (IRR) as the main outcome measure. RESULTS: The cohort contained 2263 subjects with open-angle glaucoma (OAG), 823 men and 1440 women. Surgery was performed on 2705 eyes. First documented procedures: deep sclerectomy (DS) (n = 1601), trabeculectomy (TRE) (799) and glaucoma drainage device (GDD) implantation (305) respectively. In total, 438 secondary operations were performed during the 7.5-year (median 2.25 years) follow-up period. The reoperation rates were 19% after DS, 12% after TRE, and 13% after GDD. Of the surgical procedures, 32% were performed on eyes of patients receiving statin therapy. Statin users showed no difference in reoperation rates (IRR 1.06, CI 0.82-1.37). In subgroups, no difference was observed in the reoperation rates adjusted with statin use after filtration surgery (DS, TRE) (IRR 1.06, CI 0.8-1.40) or GDD implantation (0.57, CI 0.20-1.63). CONCLUSION: Systemic statin therapy among surgically treated OAG patients had no impact on secondary surgery rates following DS, TRE or GDD implantation.

Glaucoma drainage devices / Dispositivos de drenagem para glaucoma

ABSTRACT Glaucoma drainage devices are important therapeutic options for cases of refractory glaucoma, in which trabeculectomy with antimetabolites has shown high risk of failure. There are devices with different sizes, designs and materials, and several studies have been conducted to test their safety and effectiveness. Despite known complications, their use has progressively increased in recent years, and they are the primary surgical option, in some situations. The aim of this review is to discuss the importance, mechanisms, biomaterials, results and complications of glaucoma drainage devices.

RESUMO Os dispositivos de drenagem para glaucoma são importante opção terapêutica em casos de glaucomas refratários, nos quais a trabeculectomia com antimetabólitos tem alta chance de falência. Há dispositivos com diferentes tamanhos, desenhos e materiais, e muitos estudos foram realizados para testar sua segurança e eficácia. Apesar de suas conhecidas complicações, seu uso tem aumentado progressivamente nos últimos anos, inclusive como primeira opção cirúrgica, em algumas situações. O objetivo desta revisão foi discutir a importância, os mecanismos, os biomateriais, os resultados e as complicações dos dispositivos de drenagem para glaucoma.

Integrated Intraoperative Optical Coherence Tomography in Pediatric Glaucoma Surgery.

The advent of integrated intraoperative optical coherence tomography (i2OCT) has opened the door for safer and more complex surgeries in the retina and cornea. However, to limit its use to just two subspecialties within ophthalmology is an opportunity lost for many other subspecialties. Here, we describe the use of i2OCT in pediatric glaucoma surgery. It can be used to identify Schlemm's canal, Barkan's membrane, demonstrate the corneal pathology in Haab's striae, and iris hypoplasia in cases of Axenfeld-Rieger anomaly. It can help identify drainage blebs that are filtering and those that are not, and identify successful drainage tube flushing. It has also been used to identify a ligating suture effect on a drainage tube. We describe these scenarios in relation to training and augmenting surgical techniques.

Predictive Analytics for Glaucoma Using Data From the All of Us Research Program.

PURPOSE: To (1) use All of Us (AoU) data to validate a previously published single-center model predicting the need for surgery among individuals with glaucoma, (2) train new models using AoU data, and (3) share insights regarding this novel data source for ophthalmic research. DESIGN: Development and evaluation of machine learning models. METHODS: Electronic health record data were extracted from AoU for 1,231 adults diagnosed with primary open-angle glaucoma. The single-center model was applied to AoU data for external validation. AoU data were then used to train new models for predicting the need for glaucoma surgery using multivariable logistic regression, artificial neural networks, and random forests. Five-fold cross-validation was performed. Model performance was evaluated based on area under the receiver operating characteristic curve (AUC), accuracy, precision, and recall. RESULTS: The mean (standard deviation) age of the AoU cohort was 69.1 (10.5) years, with 57.3% women and 33.5% black, significantly exceeding representation in the single-center cohort (P = .04 and P < .001, respectively). Of 1,231 participants, 286 (23.2%) needed glaucoma surgery. When applying the single-center model to AoU data, accuracy was 0.69 and AUC was only 0.49. Using AoU data to train new models resulted in superior performance: AUCs ranged from 0.80 (logistic regression) to 0.99 (random forests). CONCLUSIONS: Models trained with national AoU data achieved superior performance compared with using single-center data. Although AoU does not currently include ophthalmic imaging, it offers several strengths over similar big-data sources such as claims data. AoU is a promising new data source for ophthalmic research.

Personalising surgical treatments for glaucoma patients.

Surgical treatments for glaucoma have relied for decades on traditional filtering surgery such as trabeculectomy and, in more challenging cases, tubes. Antifibrotics were introduced to improve surgical success in patients at increased risk of failure but have been shown to be linked to a greater incidence of complications, some being potentially vision-threatening. As our understanding of glaucoma and its early diagnosis have improved, a more individualised management has been suggested. Recently the term "precision medicine" has emerged as a new concept of an individualised approach to disease management incorporating a wide range of individual data in the choice of therapeutic modalities. For glaucoma surgery, this involves evaluation of the right timing, individual risk factors, targeting the correct anatomical and functional outflow pathways and appropriate prevention of scarring. As a consequence, there is an obvious need for better knowledge of anatomical and functional pathways and for more individualised surgical approaches with new, less invasive and safer techniques allowing for earlier intervention. With the recent advent of minimally invasive glaucoma surgery (MIGS) a large number of novel devices have been introduced targeting potential new sites of the outflow pathway for lowering intraocular pressure (IOP). Their popularity is growing in view of the relative surgical simplicity and apparent lack of serious side effects. However, these new surgical techniques are still in an era of early experiences, short follow-up and lack of evidence of their superiority in safety and cost-effectiveness over the traditional methods. Each year several new devices are introduced while others are withdrawn from the market. Glaucoma continues to be the primary cause of irreversible blindness worldwide and access to safe and efficacious treatment is a serious problem, particularly in the emerging world where the burden of glaucoma-related blindness is important and concerning. Early diagnosis, individualised treatment and, very importantly, safe surgical management should be the hallmarks of glaucoma treatment. However, there is still need for a better understanding of the disease, its onset and progression, the functional and structural elements of the outflow pathways in relation to the new devices as well as their long-term IOP-lowering efficacy and safety. This review discusses current knowledge and the future need for personalised glaucoma surgery.

Experimental models of glaucoma filtration surgery.

Glaucoma filtration surgery plays an important role in achieving intraocular pressure (IOP) reduction in patients who have high IOP despite maximum medical therapy. Preclinical experimental models of glaucoma filtration surgery contribute a great deal to our knowledge of the wound healing processes that predispose to scarring and may lead to poor outcomes. However, this research needs to be interpreted in the light of the specific study design, animal model and methods used. We review the existing literature addressing various models of experimental glaucoma filtration surgery, discuss the considerations in assessing these models and describe future steps in evaluating potential therapeutics and bleb characteristics that could impact translational research in this field.

A Comparison of Subconjunctival Wound Healing between Different Methods of Dissecting Subconjunctival Tissues.

OBJECTIVE: To compare different methods for dissecting subconjunctival tissues by developing subconjunctival wound healing models. METHODS: New Zealand white rabbits were separated into 3 groups based on the method by which the rabbit subconjunctival wound healing model was generated: subconjunctival tissues were dissected episclerally (EPI) or subepithelially (SUB), with a corresponding blank control (CON). All the cases in the experimental groups were surgically prepared with conjunctival flaps, and they were sacrificed on the third postoperative day. At the surgical sites, the protein levels of hypoxia-inducible factor-1 (HIF-1)-α, vascular endothelial growth factor (VEGF)-A, and matrix metalloproteinase (MMP)-2 were detected by Western blot, morphological vascularity was measured by Adobe Photoshop, and subconjunctival fibrosis was assessed by histology. RESULTS: Compared with the CON group, both the EPI and SUB groups showed significantly upregulated protein levels of HIF-1α, VEGF-A, and MMP-2. In addition, the protein levels of HIF-1α, VEGF-A, and MMP-2 were higher in the EPI group than in the SUB group. Morphological vascularity was significantly elevated in the EPI group compared with the SUB and CON groups. Collagen content was markedly increased in the EPI group compared with the SUB and CON groups. CONCLUSIONS: Dissecting subconjunctival tissues subepithelially inhibits subconjunctival fibrosis, which may be instructive in tenonectomy in filtration surgery.

Three-Year Findings of the HORIZON Trial: A Schlemm Canal Microstent for Pressure Reduction in Primary Open-Angle Glaucoma and Cataract.

PURPOSE: To report 3-year outcomes of the HORIZON study comparing cataract surgery (CS) with Hydrus Microstent (Ivantis, Inc) implantation versus CS alone. DESIGN: Multicenter randomized clinical trial. PARTICIPANTS: Five hundred fifty-six eyes from 556 patients with cataract and primary open-angle glaucoma (POAG) treated with 1 or more glaucoma medication, washed out diurnal intraocular pressure (IOP) of 22 to 34 mmHg, and no prior incisional glaucoma surgery. METHODS: After phacoemulsification, eyes were randomized 2:1 to receive a Hydrus Microstent or no stent. Follow-up included comprehensive eye examinations through 3 years. MAIN OUTCOME MEASURES: Outcome measures included IOP, medical therapy, reoperation rates, visual acuity, adverse events, and changes in corneal endothelial cell counts. RESULTS: Three hundred sixty-nine eyes were randomized to microstent treatment and 187 to CS only. Preoperative IOP, medication use, washed-out diurnal IOP, and glaucoma severity did not differ between the two treatment groups. At 3 years, IOP was 16.7 ± 3.1 mmHg in the microstent group and 17.0 ± 3.4 mmHg in the CS group (P = 0.85). The number of glaucoma medications was 0.4 ± 0.8 in the microstent group and 0.8 ± 1.0 in the CS group (P < 0.001), and 73% of microstent group eyes were medication free compared with 48% in the CS group (P < 0.001). The microstent group included a higher proportion of eyes with IOP of 18 mmHg or less without medications compared with the CS group (56.2% vs. 34.6%; P < 0.001), as well as IOP reduction of at least 20%, 30%, or 40% compared with CS alone. The cumulative probability of incisional glaucoma surgery was lower in the microstent group (0.6% vs. 3.9%; hazard ratio, 0.156; 95% confidence interval, 0.031-0.773; P = 0.020). No difference was found in postoperative corneal endothelial cell loss between groups. No procedure- or device-related serious adverse events resulting in vision loss occurred in either group. CONCLUSIONS: Combined CS and microstent placement for mild to moderate POAG is safe, more effective in lowering IOP with fewer medications, and less likely to result in further incisional glaucoma filtration surgery than CS alone at 3 years.