Australian ophthalmologists have published the first independent head-to-head comparison of two leading minimally invasive glaucoma surgery (MIGS) devices, finding no significant difference in intraocular pressure (IOP) outcomes but a potential greater reduction in medication use in one group.
The paper was published in the peer-reviewed RANZCO journal Clinical & Experimental Ophthalmology earlier this year and compared real-world 24-month outcomes of phacoemulsification (cataract surgery) combined with either the Glaukos iStent inject or Hydrus Microstent.
The analysis was performed on data from the Fight Glaucoma Blindness (FGB) international registry, established by the Save Sight Institute in Sydney. The registry’s chief investigator Dr Mitchell Lawlor co-authored the paper.
The study featured anonymised 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 patients) or Hydrus Microstent (120 patients).
Importantly, the data was adjusted for baseline characteristics using linear regression and propensity score matching. The primary endpoint was a comparison of mean IOP at 24 months.
At 24 months, there was no significant difference in mean IOP reduction between the two groups, consistent across all analyses. The matched cohort showed iStent inject achieved a 3.1 mmHg reduction and Hydrus a 2.3 mmHg reduction (p = 0.530).
A mean medication reduction of 1.0 was reported for iStent inject versus 0.5 for Hydrus (p = 0.081). A total of 5.4% of eyes in the iStent inject group and 7.5% of eyes in the Hydrus group required subsequent procedures to improve IOP control within 24 months.
Complications were rare with no significant differences between the groups.
“Twenty-four-month outcomes showed sustained IOP reduction with a good safety profile for both groups,” the authors concluded.
“There was no significant difference in IOP outcomes between the groups. There may be a small additional reduction in glaucoma medication usage following cataract surgery with iStent inject compared to Hydrus.”
Medication use reduced
Although the crude data did not show any significant difference in the medication reduction when comparing the two groups, after adjusting for baseline characteristics, the authors reported 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 it did 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).
The proportion of eyes meeting the 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 21 mmHg at 24 months, while complete success refers to a 20% reduction from pre-op IOP with final IOP <15, 18 or 21 mmHg at 24 months on no medications.
They also stated that 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 (3-24 months). There were no cases of visually significant hyphema reported in the iStent inject group, and 3 (2.5%) were reported in the Hydrus group.
The FGB registry was officially launched during the 2017 RANZCO Congress in Perth to present a more cost-effective way to measure the long-term effects of MIGS compared with randomised trials.
Lawlor said the study was the first publication of data from the FGB registry.
“The most common situation in which MIGS devices are used in Australia is a trabecular bypass device in combination with cataract surgery. It made sense for our first analysis of the registry data to look at a comparison of the Hydrus microstent, and the iStent inject, which are the two most common MIGS devices in use in Australia,” he said.
“There have been a number of randomised trials looking at the efficacy of MIGS devices. Randomised trials provide information on a highly selected group of patients having surgery with a highly selected group of surgeons. In contrast, this study provides real world comparative data of a large and varied population of patients as part of routine clinical care. It therefore tells us what sort of outcomes surgeons can expect for patients as part of their clinical care.”
He said the study provided reassurance that surgeons should feel comfortable selecting either trans-trabecular bypass device in combination with cataract surgery, and that they will achieve clinically meaningful reductions in medication use and IOP out to at least 2 years.
“The Fight Glaucoma Blindness registry is currently tracking over 5000 individual glaucoma procedures. We are currently working on publications describing the real world outcomes from other glaucoma interventions including SLT, trabeculectomy, Xen implants, and glaucoma drainage devices,” he added.
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