Intraocular pressure (IOP) is the only modifiable risk factor in glaucoma, and its reduction continues to dominate both clinical decision-making and outcome assessment. This focus is understandable and has historical justification. However, the continued tendency to equate glaucoma control with numerical pressure targets alone reflects an increasingly outdated view of a complex and lifelong neurodegenerative disease. IOP is indispensable, but it is not the disease, nor is it the outcome that patients ultimately care about.
Glaucoma management is not a short-term exercise in achieving the lowest possible pressure but a long-term commitment to preserving visual function, maintaining structural stability, and sustaining treatment strategies that patients can realistically follow for decades. When success is narrowly defined by pressure values, clinically meaningful dimensions of care are overlooked.
From the perspective of clinicians working in high-volume tertiary glaucoma centers, it is evident that pressure-centric thinking frequently fails to predict real-world outcomes. Patients with “acceptable” IOPs continue to progress, while others remain stable with pressures that are traditionally considered suboptimal. This disconnect raises a critical question: Are we measuring what truly matters?
Minimally invasive glaucoma surgery (MIGS), particularly trabecular microbypass technologies, has revealed the limitations of conventional outcome frameworks. Initially dismissed as offering modest pressure reductions, these procedures have accumulated long-term data that challenged the assumption that greater pressure lowering is always synonymous with better long-term disease control.
Consistency Is a Clinical Outcome
One of the most underappreciated attributes of trabecular microbypass surgery is not the magnitude of IOP reduction but its consistency. Across multiple long-term studies, sustained reductions in IOP, typically 20–40%, have been demonstrated over follow-up periods of up to 5, 7, and even 8 years.1-4 More importantly, a large proportion of treated eyes maintain pressure within target ranges without the volatility often observed with medical therapy alone.
This effect is not confined to idealized trial populations. Meaningful and durable outcomes have been reported across a broad spectrum of glaucoma subtypes, including primary open-angle, pseudoexfoliative, pigmentary, and selected secondary glaucoma.
Such consistency suggests that restoring physiological outflow through Schlemm’s canal addresses a fundamental pathophysiological bottleneck rather than a narrow diagnostic category.
In daily clinical practice, reliability is often more valuable than dramatic but unpredictable reductions in pressure. However, this distinction is rarely reflected in the definition of treatment success.
Freeing MIGS From Cataract Surgery
Another enduring misconception is that the trabecular microbypass primarily derives its benefits from concurrent cataract surgery. While phacoemulsification alone modestly lowers IOP, long-term observational data clearly demonstrate that trabecular microbypass provides a significantly additive and durable benefit beyond lens extraction. Comparable outcomes have also been achieved when the procedure is performed as a standalone intervention in both phakic and pseudophakic eyes.1,2
This independence from lens status has important clinical implications. This allows intervention to be guided by the glaucoma trajectory, risk of progression, and treatment tolerance, rather than by the timing of cataract development. In other words, MIGS enables earlier and more strategic decision-making, a concept that remains underutilized in current practice.
Similarly, the baseline disease burden should no longer be viewed as a gatekeeper for surgical consideration. Although eyes with higher preoperative pressures and medication loads achieve larger absolute reductions, a clinically meaningful benefit is consistently observed even in eyes starting with relatively low IOP or limited medical therapy. This challenges the reflexive escalation model, which reserves surgery for failure rather than using it proactively to prevent it.
Medication Burden Is Not a Secondary Outcome
Despite decades of evidence, the clinical consequences of long-term topical therapies remain underestimated. Poor adherence, ocular surface disease, fluctuating pressure control, and cumulative toxicity are not theoretical concerns; they are everyday realities in glaucoma clinics.5-8
Long before surgical strategies were reconsidered, real-world observational studies demonstrated that persistence with first-line topical therapy declined rapidly, even with effective agents, exposing a fundamental gap between pharmacologic efficacy and real-life disease control.9 This gap has not narrowed over the years. As treatment regimens become increasingly complex, this has become more apparent.
Against this backdrop, the value of the trabecular microbypass becomes clearer. Longitudinal data consistently show substantial by reductions in medication burden during the early and intermediate postoperative years, with a significant proportion of patients reducing therapy and many remaining medication-free long term.1-3 Although medication use may increase again with disease progression, the years gained with a lower treatment burden are not trivial. These periods represent improved adherence, better ocular surface health, and delayed exposure to more invasive surgeries.
Our real-world experience comparing trabecular microbypass implantation with endocyclophotocoagulation as adjuncts to cataract surgery reinforces this principle: similar long-term pressure control can be achieved, but trabecular microbypass more reliably facilitates sustained reduction in medication burden with a favorable safety profile.10
Stability, Not Suppression
Perhaps the most consequential shift in the MIGS narrative is the growing signal of disease stability. Across several long-term series, visual fields and structural parameters, including the cup-to-disc ratio and retinal nerve fiber layer thickness, remain largely stable for up to 5 years, with only a small minority of eyes showing clinically significant progression at 7 years.2-4 When progression beyond this timeframe occurs, it mirrors the natural history of glaucoma rather than suggesting procedural failure.
These findings do not imply neuroprotection, nor do they suggest that MIGS replaces filtering surgery in patients with advanced disease. However, they directly challenge the entrenched belief that only aggressive pressure lowering can meaningfully alter the disease course. Stability, sustained over time, is the outcome that truly matters, and it is precisely this outcome that remains underemphasized in many treatment algorithms.
Redefining Success in Glaucoma Care
If success in glaucoma continues to be defined solely by the achievement of the lowest possible IOP, we risk prioritizing intensity over sustainability. Treatments that deliver moderate but consistent pressure reduction, minimize medication burden, preserve ocular anatomy, and maintain long-term stability may ultimately offer greater lifetime value than strategies focused exclusively on maximal pressure suppression.
Long-term data remind us that glaucoma progression is rarely eliminated, regardless of the chosen intervention. The more relevant clinical question is whether progression can be delayed safely and predictably with minimal cumulative cost to the patient. When viewed through this lens, trabecular microbypass technologies do not represent a compromise but a recalibration of priorities.
IOP will always matter in glaucoma. However, until we broaden our definition of success to include stability, sustainability, and patient-centered outcomes, we will continue to measure the disease with tools that are necessary yet fundamentally incomplete.
The views and opinions expressed here may not necessarily represent those of Bryn Mawr Communications or Cataract & Refractive Surgery Today Global.
1. Hengerer FH, Auffarth G, Conrad-Hengerer I. iStent inject trabecular micro-bypass with or without cataract surgery yields sustained 5-year glaucoma control. Adv Ther. 2022;39:1717–1731.
2. Hengerer FH, Auffarth G, Conrad-Hengerer I. 7-year efficacy and safety of iStent inject trabecular micro-bypass in combined and standalone usage. Adv Ther. 2024;41:1–15.
3. Salimi A, Watt H, Harasymowycz P. Long-term outcomes of two first-generation trabecular micro-bypass stents with phacoemulsification in primary open-angle glaucoma: eight-year results. Eye Vis (Lond). 2021;8:1–9.
4. Ziaei M, Au L. Long-term outcomes of trabecular micro-bypass surgery: stability beyond pressure reduction. J Glaucoma. 2020;29:1015–1022.
5. Okeke CO, Quigley HA, Jampel HD, et al. Adherence with topical glaucoma medication monitored electronically. Ophthalmology. 2009;116:191–199.
6. Tsai JC. A comprehensive perspective on patient adherence to topical glaucoma therapy. Ophthalmology. 2009;116(Suppl):S30–S36.
7. Baudouin C, Liang H, Hamard P, et al. The ocular surface of glaucoma patients treated long term expresses inflammatory markers. Ophthalmology. 2008;115:109–115.
8. Robin AL, Novack GD, Covert DW, et al. Adherence in glaucoma: objective measurements of once-daily and adjunctive therapy. Am J Ophthalmol. 2007;144:533–540.
9. Arias A, Schargel K, Ussa F, et al. Patient persistence with first-line antiglaucomatous monotherapy. Clin Ophthalmol. 2010;4:261–267.
10. Algorinees R, Almohizea A, Aldalgan H, Alobaida I, Schargel K, Aljohar S. Outcomes of iStent versus endocyclophotocoagulation as adjunct to cataract surgery. Eur J Ophthalmol. 2024;34:1–8.
iStent inject® IMPORTANT SAFETY INFORMATION
INDICATION FOR USE: The iStent inject, 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, 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 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 is MR-Conditional; see MRI Information below. • Physician training is required prior to use of the iStent inject 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 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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