Glaucoma management has always been complex. Balancing the best combinations of eye drops to help the patient’s disease state while avoiding the comorbidities, intolerances, and side effects can be extremely challenging. The advent of MIGS triggered a transformative shift in glaucoma treatment with an emphasis on early noninvasive surgical treatment. It still can be challenging, however, to know which medicines and procedures to use and in what order.
The original aim of MIGS surgery has not changed. These procedures have four clear advantages: (1) they are minimally traumatic, requiring only an ab interno microincision, (2) they have at least modest efficacy, (3) they have a favorable safety profile, and (4) patients typically experience rapid recovery.1 Of these, long-term safety is key to allow early intervention with beneficial risk-benefit ratio.
MIGS is typically used to treat early-stage glaucoma. It can be combined with cataract surgery to maintain safety, reduce the medication burden for patients, and preserve their refractive outcomes, which is especially crucial for patients who elect an advanced technology IOL. In a retrospective consecutive case series of 106 eyes, the iStent inject® (Glaukos) procedure was refractively neutral by 4 weeks postoperative, and 74% and 99% of eyes were within ±0.50 D and ±1.00 D of the target refraction, respectively.2
The iStent inject W has a very similar safety profile to standalone cataract surgery, including no significant difference in the rate of endothelial cell loss over 5 years.3 Studies have shown no reports of myopic shift, flat anterior chamber, choroidal hemorrhage or effusion, cyclodialysis, hypotony for 1 or more months, hypotony maculopathy, stent dislocation, significant hyphema, and corneal decompensation at up to 24 months after the iStent inject procedure.3-5
MEASURING EFFICACY BEYOND IOP
It is important to look beyond IOP when measuring the efficacy of trabecular micro-bypass procedures. While IOP reduction remains a primary goal, factors such as medication reduction, quality of life improvement, visual field stability, and reduced need for secondary glaucoma interventions should be considered. More studies are needed to look at these important parameters.
According to the long-term outcomes (up to 9 years) from multiple independent, real-world studies, iStent® technologies provide efficacy.6-10 Although the IOP reductions often differ from study to study, it is likely due to differences in baseline, demographics, and surgical approach.
A systematic review and meta-analysis of 778 eyes from 13 studies showed the efficacy of iStent devices as a standalone procedure.11 Patients were followed for 6 months to 5 years. All studies showed a level of IOP consistency across the duration of the follow-up (Figure).
Figure. IOP outcomes with the iStent technologies as a standalone procedure.
CONCLUSION
A key feature of MIGS is safety. Long-term data supports iStent as a safe procedure that combines well with phacoemulsification. Although there are few comparative studies, iStent appears to be one of the safest MIGS options, with rapid recovery and a side effect profile similar to phacoemulsification alone. Data supports the IOP-lowering and medication-reduction impact of iStent, which in turn can improve quality of life after surgery.
1. Saheb H, Ahmed IIK. Micro-invasive glaucoma surgery: current perspectives and future directions. Curr Opin Ophthalmol. 2012;23(2):96-104.
2. 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;14:517-524.
3. 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.
4. Shalaby WS, Patel S, Lam SS, et al. Hemorrhagic complications following trabecular bypass microstent surgery in the setting of antithrombotic therapy. J Glaucoma. 2023;32(5):389-395.
5. 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.
6. Berdahl JP, Voskanyan L, Myers JS, Katz JL, Samuelson TW. iStent inject trabecular micro‐bypass stents with topical prostaglandin as standalone treatment for open‐angle glaucoma: 4‐year outcomes. Clin Exp Ophthalmol. 2020;48(6):767-774.
7. 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.
8. Ferguson TJ, Mechels KB, Dockter Z, et al. iStent trabecular microbypass stent implantation with phacoemulsification in patients with open-angle glaucoma: 6-year outcomes. Clin Ophthalmol. 2020;14:1859-1866.
9. Ziaei H, Leon A. Manchester iStent study: long-term 7-year oucomes. Eye. 2021;35(8):2277-2282.
10. Salimi A, 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.
11. 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.
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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