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HomeminewsFirst iStent inject vs Hydrus Comparison

First iStent inject vs Hydrus Comparison

An independent, real-world observational study, comparing two-year outcomes of glaucoma patients who received secondgeneration iStent inject vs Hydrus Microstent, has found both groups sustained intraocular-reduction with good safety. Patients in the iStent inject group were more likely to experience a reduced burden of medication.

The peer-reviewed, multi-centre study was the first to directly compare outcomes from the two minimally invasive surgeries, with both procedures performed in combination with cataract surgery.

The peer-reviewed, multi-centre study was the first to directly compare outcomes from the two minimally invasive surgeries

Conducted by the Fight Glaucoma Blindness (FGB) international registry, the study included data from 344 eyes with mild-to-moderate open-angle glaucoma, normal-tension glaucoma or ocular hypertension that underwent phacoemulsification combined with either iStent inject (224) or Hydrus Microstent (120).

Prior studies have demonstrated the IOP-lowering efficacy of iStent inject in patients with mild-to-moderate OAG across all levels of baseline intraocular pressure (IOP) and medication burden.

In this study, patients in the Hydrus group had higher baseline IOP, greater medication use, and worse visual field mean deviation than the iStent inject group, suggesting a bias towards reserving Hydrus for patients with a higher pre-operative disease burden. This potential bias was controlled by using propensity score matching to create two balanced treatment groups for analysis.


The study confirmed that surgical selection bias driving the use of Hydrus in patients with higher pre-operative disease burden is not supported by clinical outcomes data.

Sustained IOP-lowering was achieved in both groups. In the matched cohort, the mean 24-month change in IOP was -2.3mmHg in the Hydrus group vs. -3.1mmHg in the iStent inject group, with no statistical difference between the two groups (p=0.530).

After adjusting for baseline characteristics, there was significantly greater average medication reduction in the iStent inject group (-0.9 meds) as compared to the Hydrus group (-0.4 meds) (p=0.025). The matched cohort showed a similar trend favouring iStent inject, though not reaching statistical significance due to the smaller sample size (-1.0 meds in the iStent inject group vs. -0.5 meds in the Hydrus group, p=0.081).

Good safety was reported in both groups, early hypotony occurred in one patient in the iStent inject group (1.3%) and three patients in the Hydrus group (4%), with one case of late hypotony in the Hydrus group (three to 24 months). There were no cases of visually significant hyphema reported in the iStent inject group; three (2.5%) were reported in the Hydrus group.

The proportion of eyes meeting the World Glaucoma Association (WGA) criteria for complete or qualified success in the matched cohort is shown in the table below. Qualified success refers to a ≥20% reduction from pre-op IOP with final IOP <15, 18 or 21mmHg at 24 months, while complete success refers to a 20% reduction from pre-op IOP with final IOP <15, 18 or 21mmHg at 24 months on no medications.


  1. Holmes DP, Clement CI, Nguyen V, et al. Comparative study of 2-year outcomes for Hydrus or iStent inject microinvasive glaucoma surgery implants with cataract surgery. Clin Exp Ophthalmol. 2022 Jan 25. 
  2. Singh IP, Sarkisian S, Hornbeak D, et al; iStent inject Study Group. Treatment Success Across Different Levels of Preoperative Disease Burden: Stratified Two-Year Outcomes from the Pivotal Trial of iStent inject Trabecular Micro-Bypass in Primary Open-Angle Glaucoma and Cataract. Clin Ophthalmol. 2021 Aug 3;15:3231-3240. doi: 10.2147/OPTH.S316270. PMID: 34376967; PMCID: PMC8349204. 
  3. Kuley B, Zheng CX, Zhang QE, et al. Predictors of success in selective laser Trabeculoplasty. Ophthalmol Glaucoma. 2020;3(2):97-102.