Published pivotal trials for FDA Approved/Cleared Glaucoma Drainage Devices:
A prospective, randomized, open-label, controlled multicenter clinical trial to assess the safety and efficacy of the iStent trabecular micro-bypass stent (Glaukos Corporation, Laguna Hills, CA) in combination with cataract surgery in subjects with mild to moderate open-angle glaucoma was conducted.1 A total of 240 eyes with mild to moderate open-angle glaucoma with IOP less than or equal to 24 mmHg controlled on 1 to 3 medications were randomized to undergo cataract surgery with iStent implantation (treatment group) or cataract surgery only (control). The study results met the primary outcome, with 72% of treatment eyes versus 50% of control eyes achieving the criterion (P less than 0.001). At 1 year, IOP in both treatment groups was statistically significantly lower from baseline values. Sixty-six percent of treatment eyes versus 48% of control eyes achieved greater than or equal to 20% IOP reduction without medication (P equal to 0.003). The overall incidence of adverse events was similar between groups with no unanticipated adverse device effects. The authors concluded that pressure reduction on fewer medications was clinically and statistically significantly better 1 year after stent plus cataract surgery versus cataract surgery alone, with an overall safety profile similar to that of cataract surgery alone. TRIAL REGISTRATION: ClinicalTrials.gov NCT00323284.
- iStent® Study Group 2 year follow-up
A prospective randomized controlled multicenter clinical trial to assess the long-term safety and efficacy of a single trabecular micro-bypass stent with concomitant cataract surgery versus cataract surgery alone for mild to moderate open-angle glaucoma was conducted.2 Eyes with mild to moderate glaucoma with an unmedicated IOP of 22 mm Hg or higher and 36 mm Hg or lower were randomly assigned to have cataract surgery with iStent trabecular micro-bypass stent implantation (stent group) or cataract surgery alone (control group). Patients were followed for 24 months postoperatively. The results showed the incidence of adverse events was low in both groups through 24 months of follow-up. At 24 months, the proportion of patients with an IOP of 21 mm Hg or lower without ocular hypotensive medications was significantly higher in the stent group than in the control group (P equal to .036). Overall, the mean IOP was stable between 12 months and 24 months (17.0 mm Hg plus or minus 2.8 [SD] and 17.1 plus or minus 2.9 mm Hg, respectively) in the stent group but increased (17.0 plus or minus 3.1 mm Hg to 17.8 plus or minus 3.3 mm Hg, respectively) in the control group. Ocular hypotensive medication was statistically significantly lower in the stent group at 12 months; it was also lower at 24 months, although the difference was no longer statistically significant. The authors concluded that patients with combined single trabecular micro-bypass stent and cataract surgery had significantly better IOP control on no medication through 24 months than patients having cataract surgery alone. Both groups had a similar favorable long-term safety profile.
- CyPass® Study Group - The COMPASS Trial
A multicenter (24 US sites), interventional randomized clinical trial (RCT) (ClinicalTrials.gov identifier, NCT01085357) was conducted to evaluate the CyPass® device.3 Subjects were enrolled beginning July 2011, with study completion in March 2015. Subjects had POAG with mean diurnal unmedicated IOP 21-33 mmHg and were undergoing phacoemulsification cataract surgery. After completing cataract surgery, subjects were intraoperatively randomized to phacoemulsification only (control) or supraciliary microstenting with phacoemulsification (microstent) groups (1:3 ratio). Microstent implantation via an ab interno approach to the supraciliary space allowed concomitant cataract and glaucoma surgery. The results of 505 subjects showed that 131 were randomized to the control group and 374 were randomized to the microstent group. Baseline mean IOPs in the control and microstent groups were similar: 24.5 plus or minus 3.0 and 24.4 plus or minus 2.8 mmHg, respectively (P greater than 0.05); mean medications were 1.3 plus or minus 1.0 and 1.4 plus or minus 0.9, respectively (P greater than 0.05). There was early and sustained IOP reduction, with 60% of controls versus 77% of microstent subjects achieving greater than or equal to 20% unmedicated IOP lowering versus baseline at 24 months (P equal to 0.001; per-protocol analysis). Mean IOP reduction was down 7.4 mmHg for the microstent group versus down 5.4 mmHg in controls (P less than 0.001), with 85% of microstent subjects not requiring IOP medications at 24 months. Mean 24-month medication use was 67% lower in microstent subjects (P less than 0.001); 59% of control versus 85% of microstent subjects were medication free. Mean medication use in controls decreased from 1.3 plus or minus 1.0 drugs at baseline to 0.7 plus or minus 0.9 and 0.6 plus or minus 0.8 drugs at 12 and 24 months, respectively, and in the microstent group from 1.4 plus or minus 0.9 to 0.2 plus or minus 0.6 drugs at both 12 and 24 months (P less than 0.001 for reductions in both groups at both follow-ups vs. baseline). No vision-threatening microstent-related AEs occurred. Visual acuity was high in both groups through 24 months; greater than 98% of all subjects achieved 20/40 best-corrected visual acuity or better. The authors concluded that this RCT demonstrated safe and sustained 2-year reduction in IOP and glaucoma medication use after microinterventional surgical treatment for mild-to-moderate POAG.
Alcon Research issued a voluntary market withdrawal of the CyPass® Micro-Stent from the global market. The firm announced the voluntary market withdrawal was based on five-year post-surgery data from the COMPASS-XT long-term safety study. The study demonstrated a clinically and statistically significant increase in corneal endothelial cell loss reported in the CyPass® Micro-Stent group compared to the cataract surgery-only control group.
The XEN45® device received 510(k) FDA clearance based on having a similar mechanism (subconjunctival pathway) to “gold standard” filtration procedures (i.e., trabeculectomy and tube shunts), demonstrating “substantial equivalence” in the pivotal prospective study of patients with refractory glaucoma.4 The study design was a single-arm, open-label, multicenter clinical study to evaluate the intraocular pressure (IOP)-lowering performance and safety of an ab interno gelatin stent (XEN45® Gel Stent, Allergan plc, Irvine, California, USA), a minimally invasive glaucoma surgery device, in refractory glaucoma. Following mitomycin C pretreatment, the stent was placed ab interno in patients who failed prior filtering/cilioablative procedure or had uncontrolled IOP on maximum-tolerated medical therapy, with medicated IOP greater than or equal to 20 and less than or equal to 35 mm Hg and visual field mean deviation less than or equal to -3 dB. Primary performance outcomes: patients (%) achieving greater than or equal to 20% IOP reduction from baseline on the same or fewer medications and mean IOP change from baseline at month 12. Procedure-related complications and ocular adverse events (AEs) were assessed. The results show sixty-five patients were implanted (intent-to-treat/safety population). At 12 months, 75.4% (46/61; observed data) reported greater than or equal to 20% IOP lowering from baseline on the same or fewer medications. Mean IOP change from baseline was -9.1 mm Hg (95% confidence interval [CI]: -10.7, -7.5) (n equal to 52; observed data) at 12 months, excluding patients with missing data (n equal to 4) and those requiring a glaucoma-related secondary surgical intervention (n equal to 9). Mean medication count decreased from 3.5 (baseline) to 1.7 (12 months). No intraoperative complications or unexpected postoperative AEs were reported. Most AEs were mild/moderate; common AEs included needling (without sight-threatening complications), nonpersistent loss of best-corrected visual acuity, and transient hypotony (requiring no surgical intervention). The authors concluded that the gelatin stent reduced IOP and medication use without raising unexpected safety concerns, offering a minimally invasive surgical option for refractory glaucoma patients.
Equivalency was further established by a relatively large retrospective cohort study comparing XEN45® with trabeculectomy, finding “no detectable difference in risk of failure and safety profiles”.5 The study design was an International, multicenter, retrospective interventional cohort study to compare the efficacy, safety, and risk factors for failure of standalone ab interno gel microstent implantation with mitomycin C (MMC) versus trabeculectomy with MMC. The participants included three hundred fifty-four eyes of 293 patients (185 microstent and 169 trabeculectomy) with no prior incisional surgery. Consecutive eyes with uncontrolled glaucoma underwent microstent or trabeculectomy surgery from January 1, 2011 through July 31, 2015 at 4 academic ophthalmology centers. The results reported baseline characteristics were similar, except more men (56% vs. 43%), younger patients (average, by 3 years), better preoperative visual acuity (22% vs. 32% with 0.4 logarithm of the minimum angle of resolution vision or worse), and more trabeculoplasty (52% vs. 30%) among microstent eyes. The adjusted HR of failure of the microstent relative to trabeculectomy was 1.2 (95% confidence interval [CI], 0.7-2.0) for complete success and 1.3 (95% CI, 0.6-2.8) for qualified success, and similar for other outcomes. Time to 25% failure was 11.2 months (95% CI, 6.9-16.1 months) and 10.6 months (95% CI, 6.8-16.2 months) for complete success and 30.3 months (95% CI, 19.0-infinite months) and 33.3 months (95% CI, 25.7-46.2 months) for qualified success. Overall, white ethnicity was associated with decreased risk of failure (adjusted HR, 0.49; 95% CI, 0.25-0.96), and diabetes was associated with increased risk of failure (adjusted HR, 4.21; 95% CI, 2.10-8.45). There were 117 and 165 distinct interventions: 43% and 31% underwent needling, respectively, and 50% of trabeculectomy eyes underwent laser suture lysis. There were 22 and 30 distinct complications, although most were transient. Ten percent and 5% underwent reoperation (P equal to 0.11). The authors concluded that there was no detectable difference in risk of failure and safety profiles between standalone ab interno microstent with MMC and trabeculectomy with MMC.
- iStent inject® Pivotal Trial under Investigational Device Exemption (IDE)
The aim of the iStent inject® Pivotal Trial (Protocol GC-008) under IDE G100326 was to establish a reasonable assurance of safety and effectiveness of the iStent inject for use in conjunction with cataract surgery for the reduction of intraocular pressure (IOP) in adult patients with mild to moderate primary open-angle glaucoma (OAG). Data from this clinical study were the primary basis for the PMA approval decision.
The iStent inject® U.S. IDE pivotal study was a prospective, randomized, multicenter clinical trial that included 40 investigational sites and 505 mild-to-moderate POAG eyes that were randomized to receive iStent inject in combination with cataract surgery (n equal to 387) or cataract surgery only (n equal to 118.) The pivotal trial data show that the iStent inject® achieved a statistically significant reduction in unmedicated diurnal IOP in patients undergoing cataract surgery at 24 months as 75.8% of the iStent inject® cohort achieved a 20% or greater reduction in unmedicated IOP and the mean unmedicated IOP reduction was 7.0 mmHg for the iStent inject cohort. In addition to meeting the study’s primary and secondary effectiveness endpoints, at 24 months, observed data show the iStent inject cohort achieved a 31% mean reduction, or 7.7 mmHg, in unmedicated IOP from an unmedicated mean baseline IOP of 24.8 mmHg to 17.1 mmHg. Finally, through 24 months, the overall rate of adverse events for the iStent inject® cohort was similar to cataract surgery alone.
- Prospective Randomized Trial comparing Hydrus Microstent and iStent Microinvasive Glaucoma Surgery Implants for Standalone Treatment of open-Angle Glaucoma: The COMPARE Study. Comparison of clinical outcome (lowering of IOP and reduction in medication requirements) for 154 patients randomized to receive either I Hydrus Microstent or 2 iStent Trabecular Micro Bypass devices for treatment of open-angle glaucoma (OAG) was made to compare efficacy of the two devices. Previous studies(Katz, Donnenfeld, Voskanyan, Fes, Pfeiffer, Samuelson (Horizon) utilizing one device (iStent) have suggested inferiority of a single iStent compared to a single Hydrus Microstent in both standalone and with Cataract Extraction procedures. Decrease in IOP was contradictive in two studies (Katz, Donnenfeld) related to the placement of a second device when baseline IOP was equivalent (20+.1). However, the addition of the second iStent (in the non-randomized studies) appears to allow for similar reduction in IOP and medication reduction in both standalone and with CE. The COMPARE Study of the two standalone MIGS in OAG, without CE, resulted in a higher surgical success rate and fewer medications for patients treated with the Hydrus Microstent compared with the 2-iStent Procedure.
Evidence-Based Guideline:
- According to the 2015 American Academy of Ophthalmology (AAO) POAG Preferred Practice Pattern (PPP), the “potential benefits of a combined procedure (cataract extraction with IOL implantation and trabeculectomy) are protection against the IOP rise that may complicate cataract surgery alone, the possibility of achieving long-term glaucoma control with a single operation, and elimination of the risk of bleb failure with subsequent cataract surgery when glaucoma surgery is performed first. Therefore, an ophthalmologist may reasonably choose to perform a combined surgery because of these perceived advantages to an individual patient. Other types of glaucoma surgery can also be combined with cataract surgery, such as implantation of aqueous shunts, nonpenetrating glaucoma surgery, minimally invasive glaucoma surgery, and endocyclophotocoagulation.”