The population is aging, and the prevalence of glaucoma is on the rise. In Western Europe alone, diagnosed and undiagnosed primary open-angle glaucoma (POAG) are projected to increase by 8.6% and 13.7%, respectively, from 2020 to 2026.1 The challenge with glaucoma management lies not only with the growing number of diagnosed cases overall but also with late-stage diagnoses. Patients with advanced disease often have irreversible visual field loss.
Traditionally, the first-line treatment for glaucoma is medication, followed by laser and then more invasive surgery. Unfortunately, this treatment paradigm comes at a steep cost. Less than 50% of patients adhere to their prescribed medication regimen after 12 months,2 and intervention for advanced disease is more costly.3 The economic costs of glaucoma management outside the health and social care system constitute about 85% of total expenses.4 Shifting to an early interventional mindset therefore is key to reduce health care costs, prevent disease progression, and improve the overall quality of life for glaucoma patients.
MIGS procedures, including devices like the iStent inject® W (Glaukos), address the challenges associated with late-stage glaucoma diagnosis and noncompliance with topical medications. These procedures can be performed in patients with mild to moderate glaucoma, offering a more efficient approach to disease management.
THE LATEST-GENERATION iSTENT
The evolution of iStent®spans 2 decades. The first-generation device was relatively complicated to implant in the trabecular meshwork, but the latest generation, iStent inject W, is more straightforward. In my hands, I can perform the procedure elegantly due to the device’s enhanced visibility. The iStent inject W also includes observable positioning confirmation to ensure the device is implanted safely, efficiently, and seamlessly.
The iStent inject W is implanted into the trabecular meshwork. There are four outflow pathways on the sides and one at the tip of the implant. The flange, visible during injection, stabilizes the implant in the trabecular meshwork. The injection system is very straightforward to use; two stents are included in each injector. The injector has two buttons; the first and second buttons are depressed to retract the sleeve of the trocar when the anterior segment is entered and deliver the stents perpendicularly into the trabecular meshwork, respectively. Once the first stent is delivered, the injector is moved 2 clock hours away on the nasal side of the trabecular meshwork, and the second one is implanted, again perpendicular to the trabecular meshwork. Only a small tenting of the sclera is required for implantation.
The anterior segment OCT scans in Figure 1 show the location of the iStent inject W in the trabecular meshwork. Note the improvement in the diameter of the Schlemm canal both nasally as well as temporally, signifying an increased pathway for aqueous outflow.5 Additionally, an angiography study found improved drainage of aqueous fluid in the episcleral veins immediately after surgery when the stents are placed 2 to 3 clock hours apart.6
Figure 1. The location of the iStent inject in the trabecular meshwork as seen on anterior segment OCT.
The iStent technologies can achieve a significant decrease in IOP across various stages of glaucoma disease as a standalone procedure and in combination with cataract surgery.7,10 Long-term studies on the iStent technologies show the stability of visual fields over 7 years regardless of glaucoma stage, optic nerve cupping, and retinal nerve fiber layer thickness.11,12
Intervening with iStent inject® W earlier in the disease pathway results in fewer secondary surgical interventions compared to intervening later (Figure 2). In a retrospective study of 333 patients undergoing trabecular bypass surgery, the rate of postoperative hyphema was four times greater with the Hydrus Microstent (Alcon) than the iStent inject in the setting of antithrombotic therapy.13
Figure 2. Intervening with iStent inject W earlier in the disease pathway results in fewer secondary surgical interventions compared to intervening later.
Additionally, the rate of postoperative peripheral anterior synechiae in the Hydrus pivotal trial14 was almost 10 times greater than in the iStent inject pivotal trial.15 Evidence from pivotal trials also showed the proportion of patients experiencing more than 30% endothelial cell loss at 5 years was lower in the iStent versus other micro-bypass stent procedures (Figure 3).8,16,17
Figure 3. Endothelial cell loss at 5 years.
CONCLUSION
The iStent technologies have evolved from an unproven technology in 2012 to an efficient solution for glaucoma. Long-term data have showed predictable reduction in IOP,10visual outcomes,18 and safety.8,14 The device is proven to stabilize visual fields over the long term11,12 with a low rate of secondary surgical interventions when used early in the disease state.11,14,19 This device is playing a crucial role to improve patients’ quality of life as we continue to move toward early glaucoma intervention and navigate an aging population.
1. Market Scope Glaucoma Device Report. Market Scope. 2021.
2. Nordstrom BL, Friedman DS, Mozaffari E, Quigley HA, Walker AM. Persistence and adherence with topical glaucoma therapy. Am J Ophthalmol. 2005;140(4): 598-e1.
3. Traverso CE, et al. Direct costs of glaucoma and severity of the disease: a multinational long term study of resource utilisation in Europe. Br J Ophthalmol. 2005;89(10):1245-1249.
4. Time to Focus Report (Fight for Sight).
5. Gillmann K, Mansouri K, Ambresin A, Bravetti GE, Mermoud A. A prospective analysis of iStent inject microstent implantation: surgical outcomes, endothelial cell density, and device position at 12 months. J Glaucoma. 2020;29(8):639-647.
6. Huang AS, Penteado RC, Papoyan V, Voskanyan L, Weinreb RN. Aqueous angiographic outflow improvement after trabecular microbypass in glaucoma patients. Ophthalmology Glaucoma. 2019;2(1):11-21.
7. Samuelson TW, Singh IP, Williamson BK, et al. Quality of life in primary open-angle glaucoma and cataract: an analysis of VFQ-25 and OSDI from the iStent inject® pivotal trial. Am J Ophthalmol. 2021;229:220-229.
8. Ahmed IIK, Sheybani A, De Francesc T, et al. Long-term endothelial safety profile with iStent inject in patients with open-angle glaucoma. Am J Ophthalmol. 2023;252:17-25.
9. Boodhna, Trishal, and David P. Crabb. “Disease severity in newly diagnosed glaucoma patients with visual field loss: trends from more than a decade of data.” Ophthalmic and Physiological Optics 35.2 (2015): 225-230.
10. Healey PR, Clement CI, Kerr NM, Tilden D, Aghajanian. Standalone iStent trabecular micro-bypass glaucoma surgery: a systematic review and meta-analysis. J Glaucoma 2021;30(7):606-620.
11. Hengerer FH, Auffarth GU, Conrad-Hengerer I. iStent inject trabecular micro-bypass with or without cataract surgery yields sustained 5-year glaucoma control. Advances in Therapy. 2022;39(3):1417-1431.
12. Ziaei H, Leon A. Manchester iStent study: long-term 7-year oucomes. Eye. 2021;35(8):2277-2282.
13. Shalaby WS, Patel S, Lam, S, et al. Hemorrhagic complications following trabecular bypass microstent surgery in the setting of antithrombotic therapy. J Glaucoma. 2023;32(5):389-395.
14. Samuelson TW, et al. Prospective, randomized, controlled pivotal trial of an ab interno implanted trabecular micro-bypass in primary open-angle glaucoma and cataract: two-year results. Ophthalmology. 2019;126(6):811-821.
15. Samuelson TW, et al. A Schlemm canal microstent for intraocular pressure reduction in primary open-angle glaucoma and cataract: the HORIZON study. Ophthalmology. 2019;126(1):29-37.
16. Ahmed IIK, De Francesco T, Rhee D, et al. Long-term outcomes from the HORIZON randomized trial for a Schlemm’s canal microstent in combination cataract and glaucoma surgery. Ophthalmology. 2022;129(7):742-751.
17. Reiss G, Clifford B, Vold S, et al. Safety and effectiveness of CyPass supraciliary micro-stent in primary open-angle glaucoma: 5-year results from the COMPASS XT study. Am J Ophthalmol. 2019;208:219-225.
18. Ioannidis AS, Töteberg-Harms M, Hamann T, Hodge C. Refractive outcomes after trabecular micro-bypass stents (iStent inject) with cataract extraction in open-angle glaucoma. Clin Ophthalmol. (2020):517-524.
19. Ali S, Watt H, Harasymowycz P. Long-term outcomes of two first-generation trabecular micro-bypass stents (iStent) with phacoemulsification in primary open-angle glaucoma: eight-year results. Eye and Vision. 2021;8(1):1-12.
INDICATION FOR USE: The iStent inject® W, is intended to reduce intraocular pressure safely and effectively in patients diagnosed with primary open-angle glaucoma, pseudo-exfoliative glaucoma or pigmentary glaucoma. The iStent inject® W, can deliver two (2) stents on a single pass, through a single incision. The implant is designed to stent open a passage through the trabecular meshwork to allow for an increase in the facility of outflow and a subsequent reduction in intraocular pressure. The device is safe and effective when implanted in combination with cataract surgery in those subjects who require intraocular pressure reduction and/or would benefit from glaucoma medication reduction. The device may also be implanted in patients who continue to have elevated intraocular pressure despite prior treatment with glaucoma medications and conventional glaucoma surgery. CONTRAINDICATIONS: The iStent inject® W System is contraindicated under the following circumstances or conditions: • In eyes with primary angle closure glaucoma, or secondary angle-closure glaucoma, including neovascular glaucoma, because the device would not be expected to work in such situations. • In patients with retrobulbar tumor, thyroid eye disease, Sturge-Weber Syndrome or any other type of condition that may cause elevated episcleral venous pressure. WARNINGS/PRECAUTIONS: • For prescription use only. • This device has not been studied in patients with uveitic glaucoma. • Do not use the device if the Tyvek® lid has been opened or the packaging appears damaged. In such cases, the sterility of the device may be compromised. • Due to the sharpness of certain injector components (i.e. the insertion sleeve and trocar), care should be exercised to grasp the injector body. Dispose of device in a sharps container. • iStent inject® W is MR-Conditional; see MRI Information below. • Physician training is required prior to use of the iStent inject® W System. • Do not re-use the stent(s) or injector, as this may result in infection and/or intraocular inflammation, as well as occurrence of potential postoperative adverse events as shown below under “Potential Complications.” • There are no known compatibility issues with the iStent inject® W and other intraoperative devices. (e.g., viscoelastics) or glaucoma medications. • Unused product & packaging may be disposed of in accordance with facility procedures. Implanted medical devices and contaminated products must be disposed of as medical waste. • The surgeon should monitor the patient postoperatively for proper maintenance of intraocular pressure. If intraocular pressure is not adequately maintained after surgery, the surgeon should consider an appropriate treatment regimen to reduce intraocular pressure. • Patients should be informed that placement of the stents, without concomitant cataract surgery in phakic patients, can enhance the formation or progression of cataract. ADVERSE EVENTS: Please refer to Directions For Use for additional adverse event information. CAUTION: Please reference the Directions For Use labelling for a complete list of contraindications, warnings and adverse events.
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