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iStent: A Powerful, Predictable, and Proven Technology

A summary of five previously published studies.

INTRODUCTION

Since the introduction of the MIGS category, the iStent, iStent inject, and iStent inject W devices have been a standard of care for the surgical treatment of mild-to-moderate glaucoma worldwide. Whether combined with cataract surgery or implanted as a standalone procedure, studies show the iStent devices significantly reduce IOP1-3 and the mean number of topical medications needed to control IOP. In many cases, trabecular micro-bypass stenting eliminates the need for glaucoma medication entirely.1,4,5 By intervening at the time of cataract surgery, iStent technology may delay the need for more invasive or bleb-forming surgeries,1 reduce the number of follow-up appointments,4 and potentially reduce medication and health costs6 making it easier for physicians to meet the current and future needs of their patients.

Five-year data on the iStent inject is now available. The overarching results from the five studies outlined herein demonstrate that the device can reliably decrease IOP in combination with cataract surgery or as a standalone procedure while reducing patients’ medication burdens and providing predictable and consistent refractive outcomes.1-9 The iStent devices are a powerful, predictable, and proven technology (see the accompanying sidebar).

POWERFUL TECHNOLOGY FOR SUSTAINED IOP AND MEDICATION REDUCTION

Hengerer and colleagues evaluated the effectiveness and safety of the iStent inject for the treatment of OAG in two settings—combined with cataract surgery and as a standalone intervention.1 A total of 125 patients were enrolled in the prospective longitudinal study, and a subgroup analysis was performed to determine results for combination and standalone treatment groups. The 5-year follow-up was completed by 121 eyes (97%), and results are shown in Figure 1.

Figure 1. Data from 121 patients at 5 years postoperative showed a 40% reduction in IOP with the iStent inject.

Overall cohort. The mean IOP decreased from 23.5 mm Hg ±6.2 mm Hg preoperatively to 14.1 ±1.8 mm Hg at 5 years postoperatively, representing a 40% reduction from baseline (P <.001). Mean medications also decreased, from 2.68 ±1.02 preoperatively to 0.77 ±0.82 at 5 years postoperatively, indicating a 71% reduction (P <.001) after patients received the iStent inject. Additionally, before surgery, 99% of eyes were on medication, and by 5 years postoperative 46% were medication-free (P <.001).

At the final follow-up visit, most eyes (83%) had achieved a reduction of IOP of 20% or greater, and all eyes had either maintained or reduced their medication burden compared to baseline. No eye required filtration surgery through the 5 years of follow-up. Lastly, visual fields, retinal nerve fiber layer thickness, and cup-to-disc ratio, which are all long-term indicators of disease stability, were unchanged throughout the duration of the study.

Combined group. A total of 81 eyes underwent iStent inject implantation combined with cataract surgery. The mean IOP decreased from 22.6 mm Hg to 13.8 mm Hg, representing a 39% decrease (P <.001). Medication usage also decreased, from 2.52 preoperatively to 0.78 at 5 years postoperatively (P <.001). This represented a 69% decrease in medication use in this group.

Standalone group. In these 44 patients, the mean IOP improved from 25.3 mm Hg before surgery to 14.6 mm Hg at 5 years postoperatively (P <.001), representing a 42% decrease. Additionally, medication use decreased from 2.98 preoperatively to 0.74 at 5 years postoperatively (P <.001). This was a 75% decrease.

Conclusion. IOP reduction was both significant and durable 5 years after iStent inject implantation. There was nearly a 2-medication reduction at the study’s conclusion.

In their prospective, randomized, controlled study, Samuelson and colleagues showed that the safety of the iStent inject procedure combined with cataract surgery is similar to cataract surgery alone.2 All patients had mild to moderate primary open-angle glaucoma and a washed out diurnal IOP between 21 and 36 mm Hg. A total of 387 eyes that received the iStent inject at the time of cataract surgery, and 118 that received cataract surgery alone, were followed for 2 years.

Results. At the 2-year follow-up, most patients in the iStent inject group (75.8%) achieved a 20% reduction in unmedicated diurnal IOP, compared to 61.9% of eyes in the control group (P < .005). Additionally, the mean reduction in unmedicated diurnal IOP from preoperative to 2 years postoperative was greater in the eyes that received the iStent inject (7.0 ±4.0 mm Hg vs 5.4 ±3.7 mm Hg; P < 0.001), and 84% and 67% of iStent inject and control eyes, respectively, were not on ocular hypotensive medication at 23 months. At 2 years, more eyes in the iStent inject group had a medication-free diurnal IOP of 18 mm Hg or less, versus control (63.2% vs 50.0%, respectively). At the 2-year follow-up, the overall safety profile was similar in both groups.

Conclusion. The researchers concluded that, combined with cataract surgery, the iStent inject produced clinically and statistically greater reductions in IOP without medication compared to cataract surgery alone.

In a study conducted by Schweitzer and colleagues, implantation of either the iStent or iStent inject combined with cataract surgery resulted in significant improvements in ocular surface health, IOP, and topical medication usage.3

A total of 47 eyes with mild to moderate OAG were enrolled. All were on at least one but no more than 4 glaucoma medications.

Results. Preoperatively, 73% of eyes had moderate or severe ocular surface disease index (OSDI) scores; the mean score was 40.1 ±21.6 At 3 months postoperatively, only 29% of eyes had a moderate or severe OSDI score, and the mean score improved to 17.5 ±15.3 (P <.0001). The mean tear breakup time improved from 4.3 ±2.4 seconds (preoperatively) to 6.4 ±2.5 seconds at 3 months (P <.0001). The mean IOP decreased from 17.4 ±4.2 mm Hg preoperatively to 14.5 ±34.2 mm Hg at 3 months postoperatively (P <.0001), and the number of glaucoma medications decreased from 1.5 preoperatively to 0.9. This represented a 60% reduction in medication burden. Furthermore, 55% of eyes were medication-free at 3 months postoperative compared to 0% at baseline.

OVERVIEW OF 5-YEAR RESULTS WITH THE ISTENT AND ISTENT INJECT

Powerful

  • In a recent study, 81% of patients who received the iStent inject with or without cataract surgery had an IOP below 15 mm Hg at 5 years versus only 2% at baseline.1
  • In that same study, there was a 40% reduction in IOP and a 71% reduction in medication burden. Only 2% of the cohort was on three or more medications at 5 years versus more than 60% at baseline.1
  • Another study showed significant improvements in both objective and subjective measures of ocular surface health were achieved after the iStent or iStent inject procedure.3 In particular, the mean ocular surface disease index score improved from 40.1 (severe ocular surface disease) to 17.5 (mild ocular surface disease) by 3 months postoperative. The authors noted that the primary factor contributing to the improvement was the significant reduction in medications.

Predictable

  • A study from 2020 demonstrated that 99% of patients were within ±1.00 D of the refractive target and 74% were within ±0.50 D.8
  • Another study confirmed that the safety of the iStent and iStent inject procedure is similar to cataract surgery alone.2
  • In a survey sent to UK ophthalmologists, respondents reported that patients who received the iStent had fewer follow-up visits compared to those who had undergone traditional glaucoma procedures and other MIGS procedures.9

Proven

  • More than 200 peer-reviewed studies have been published on the iStent technology.
  • More than 20 years of data, including preclinical data, are available for the iStent technology.
  • Study results to date include more than 20,000 eyes.
  • The iStent technologies are used in more than 20 countries worldwide.
  • More than 900,000 iStent devices have been implanted worldwide to date.

PREDICTABLE PROCEDURE REDUCING FOLLOW-UP VISITS

A UK national survey conducted by Rodriguez-Una and colleagues and sent to 75 glaucoma specialists showed that patients who received the iStent required fewer follow-up visits compared to those who had undergone traditional glaucoma procedures (trabeculectomy, tube surgery) and other MIGS procedures (Figure 2).8

Figure 2. Patients required fewer follow-up visits in the first 6 months after surgery with the iStent compared to other glaucoma procedures.8

Number of follow-up visits. On average, iStent patients required three follow-up visits in 6 months. Trabeculectomy required more follow-up than any other intervention, followed by tube surgery (nine and seven follow-up visits in 6 months, respectively). Nonpenetrating deep sclerectomy on average required five follow-ups in 6 months.

Conclusion. iStent surgery required the fewest follow-up appointments.

PROVEN REFRACTIVELY NEUTRAL

Ioannidis and colleagues combined laser cataract surgery with the implantation of two iStent inject devices in 106 eyes of 89 patients to determine the refractive outcomes and the potential implications of combined surgery in patients with open-angle glaucoma.8

Results. The mean absolute difference in the target refraction from baseline to the 4-week postoperative visit was 0.36 ±0.25 D. Most eyes (73.9%) were within ±0.50 D of intended refraction, and 98.9% were within ±1.00 D. Of the eyes with preoperative astigmatism, the residual astigmatism was 0.50 D or less in 73.8% (Figure 3).

Figure 3. The refractive outcomes from OAG patients who received the iStent inject with cataract extraction.

Conclusion. Refractive outcomes were predictable and consistent after combining laser cataract surgery with the implantation of two iStent inject devices.

1.. Hengerer FH, Auffarth GU, Conrad-Hengerer I. iStent inject trabecular micro-bypass with or without cataract surgery yields sustained 5-year glaucoma control. Adv Ther. doi:10.1007/s12325-021-02039-4

2. Samuelson TW, Sarkisian SR, Lubeck DM, 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.

3. Schweitzer JA, Hauser WH, Ibach M, et al. Prospective interventional cohort study of ocular surface disease changes in eyes after trabecular micro-bypass stent(s) implantation (iStent or iStent inject) with phacoemulsification. Ophthalmol Ther. doi:10.1007/s40123-020-00290-6

4. Healey PR, Clement CI, Kerr NM, Tilden D, Aghajanian L. Standalone iStent trabecular micro-bypass glaucoma surgery: a systematic review and meta-analysis. J Glaucoma. Published ahead of print, 2021.

5. Lindstrom R, Sarkisian SR, Lewis R, Hovanesian J, Voskanyan L. Four-year outcomes of two second-generation trabecular micro-bypass stents in patients with open-angle glaucoma on one medication. Clin Ophthalmol. 2020;14:71-80.

6. Guedes RAP, Gravina DM, Lake JC, Guedes VMP, Chaoubah A. Intermediate results of iStent or iStent inject implantation combined with cataract surgery in a real-world setting: a longitudinal retrospective study. Ophthalmol Ther. 2019;8:87

7. Ngan K, Fraser E, Buller S, Buller A. A cost minimisation analysis comparing iStent accompanying cataract surgery and selective laser trabeculoplasty versus topical glaucoma medications in a public healthcare setting in New Zealand. Graefes Arch Clin Exp Ophthalmol. 2018;256: 2181

8. Rodriguez-Una I, Azuara-Blanco A, King AJ. Survey of glaucoma surgical preferences and postoperative care in the United Kingdom. Clin Exp Ophthalmol. 2017;45:232-240.

9. Ioannidis AS, Töteberg-Harms M, Hamann T, Hodge C. Refractive outcomes after trabecular micro-bpass stents (iStent inject) with cataract extraction in open-angle glaucoma. Clin Ophthalmol. 2020;14:517-524.

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