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iStent MIGS devices associated with less visual field progression in glaucoma compared with medical therapy

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(Image Credit: AdobeStock/Ayesha)

(Image Credit: AdobeStock/Ayesha)

A recent study found implantation of the various iStent microbypass stent technologies (Glaukos) resulted in less progression of glaucoma annually compared with medical therapy,1 according to study coauthors Kevin Gillmann, MD, PhD, MBBS, MBA, FEBO, MArch, PgCert, Genève Ophtalmologie, Geneva, Switzerland, and Stanford University, Palo Alto, CA, and Dana M. Hornbeak, MD, MPH, from Glaukos Corp., Aliso Viejo, CA.

The iStent (1 stent), the iStent inject and iStent inject W (2 stents), and the iStent infinite (3 stents) are the 4 currently marketed iStent technologies.

Gillmann and Hornbeak explained that the current focus of glaucoma management tends to be on lowering the intraocular pressure (IOP); however, the ultimate goal is preservation of functional vision and quality of life.2

The World Glaucoma Association consensus group and others, they pointed out, have been urging a shift in the focus of glaucoma clinical trials toward biomarkers that better represent disease stability, such as structural, functional or even composite endpoints, in order to improve decision-making in glaucoma.3,4

In light of this interest, the investigators conducted this study to fill a gap in the medical literature regarding the long-term effect of minimally invasive glaucoma surgeries (MIGS) on visual field progression. They noted that cohorts with treated glaucoma exhibited mean visual field progression rates ranging from −0.22 to −0.67 decibels (dB) annually.

Medical literature search

The investigators searched electronic medical literature databases to find studies on iStent technologies. A total of 15 studies with 1,115 eyes were identified that had follow-up times of 12 months or longer, patient retention rates of 75% and more, and included visual field data.

Gillmann and Hornbeak reported that the analysis of the data showed that the weighted mean baseline IOP was 19.0±3.1 mmHg. At the end of a 37.9-month mean follow-up period (range,12–96 months), a weighted mean 26.6% IOP reduction was achieved (range, 15.2%–42.3%). Over the same time frame, in patients with iStents, the weighted mean visual field mean deviation progression rate was −0.02±0.34 dB annually from a mean baseline of −5.76±5.68 dB.

A possible explanation for the lower progression rates may be that implantation of MIGS devices eliminates the limitations of medical therapy that affect efficacy, such as patient non-adherence, ocular surface disease, local/systemic side effects, costs, caregiving burden, IOP fluctuations, and diminished quality of life. “In this way, by intervening earlier in a patient’s treatment course, visual function may be better preserved and risk of glaucoma progression may be lessened,” they said.

The authors concluded that the iStent devices achieve a lower rate of visual field progression compared with medical therapy. They also advised that specifically designed and powered trials should be conducted to confirm these results. “The present findings suggest that early trabecular bypass surgery may be beneficial in stabilizing glaucoma progression,” they commented.

They also believe that additional research is warranted to determine the reasons behind the lack of correlation between functional progression and IOP reduction.

"In this meta-analysis of over a thousand eyes, trabecular microbypass surgery was found to stabilize glaucoma progression, leading to a mean progression rate of −0.024 dB per year. Even when examining only standalone procedures, the resulting mean functional progression rate was comparable to that in non-glaucomatous ocular hypertension and slower than in treated glaucoma. This suggests that interventional glaucoma treatments could offer a promising strategy for stabilizing functional progression and preserving patients' quality of life, particularly in the early stages of the disease."

References:
  1. Gillmann K, Hornbeak DM. Rates of visual field change and functional progression in glaucoma following trabecular microbypass implantation of iStent technologies: a meta-analysis. BMJ Open Ophthalmol.2024;9:e001575; doi:10.1136/bmjophth-2023-001575
  2. SafitriA, Konstantakopoulou E, Hu K, et al.Treatment expectations in glaucoma: what matters most to patients? Eye (Lond). 2023;37:3446–54. doi: 10.1038/s41433-023-02532-w
  3. WeinrebRN, RamuluP, TopouzisF, et al.11th Consensus Meeting: Glaucoma Surgery. Melbourne, Australia, Kugler Publications, 2019.
  4. MedeirosFA.Biomarkers and surrogate endpoints in glaucoma clinical trials. Br J Ophthalmol. 2015;99:599–603.doi:10.1136/bjophthalmol-2014-305550
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