George Reiss, MD, of Eye Physicians & Surgeons of Arizona, discusses a study he presented at the 2025 American Glaucoma Society (AGS) Annual Meeting that compared use of iStent infinite versus Hydrus Microstent for glaucoma.
George Reiss, MD:
I’m going to talk about direct comparison of 2 different trabecular bypass implants in glaucoma. It’s a 6-month subgroup analysis based on multiple sub-analyses, including lens status as well as prior SLT status. In this study, compared to minimally invasive devices, the iStent infinite and the Hydrus Microstent, which both were designed to enhance outflow and lower intraocular pressure, this was prospective. It was done outside the United States. It involved patients who were phakic as well as patients who were pseudophakic. There were over 180 eyes and 107 subjects in 7 study sites, and the patients were randomized to either receive the Hydrus stent or the iStent infinite.
Demographics, as you’ll see, were pretty well balanced. There was 91 in the iStent Infinite group as well as 89 in the Hydrus group, and there was really very little differences in the demographics. We feel pretty comfortable that this is a good, at least, attempt to do a pilot study looking at how these devices performed against one another. The phakic eyes were 76%, approximately, were iStent, and 68% were Hydrus. In the pseudophakes, 82.4% were iStent infinite and 60.9% were Hydrus. Again, you’re seeing essentially pretty comparable groups.
Patients who had received SLT, about 50.6% were on iStent Infinite and 34% of Hydrus eyes had previous SLT. Then there was similar numbers again in both groups that were SLT-naive. This was multicenter, as I mentioned. This is a 6-month study. Obviously, it’s a pilot study. It’ll be interesting to see how these patients go forward. The interesting parts of the study has to do with the results and, at least, in these 2 groups, the differences were really pretty minimal in terms of outcomes. Specifically, if you look at patients who’ve had prior SLT, the success rate was essentially similar: 58.3% in the iStent group and 49.8% in the Hydrus group achieved the 20% reduction from baseline, which can be used as a measurement of success.
You’ll note that prior SLT seemed to have an effect in that, if you use the trabecular meshwork for SLT, at least at 6 months, you may find slightly less success in both groups. What is interesting too is in SLT-naive, the success rate was much higher in both groups: 88.9% in the iStent group and 86.4% in the Hydrus group. Really, essentially, the same and no statistical significance between those 2 groups. Phakic and pseudophakic somewhat similar with the iStent group having slightly higher success, at 76.6%, as compared to the Hydrus group, at 68.4%, in the phakic eyes. The pseudophakic eyes, similar, but there was a significant difference with the iStent group having 82.4% achieved 20% of pressure reduction as opposed to 60.9% in Hydrus, and that was statistically significant.
I think the take-home point here, and there’s some other comments I can make regarding how these groups behaved in terms of complications and so forth, but they’re really quite similar. I think my conclusion to this is that, at least, in this group, and again, it’s a only 6-months study so far, but it’s 180 eyes and 107 subjects, I think regardless of which of these devices you put in, you can expect fairly similar results. This study would tend to show that iStent is slightly more efficacious in pseudophakic eyes than Hydrus, and slightly more efficacious in SLT-naive eyes. The numbers, basically, would give good comfort to whichever device a surgeon decides to use.
I think there are big differences between the 2 devices, and I’m going to speak to that from my personal experience, but the study would tend to give good support to the use of either of these. That comes back to my general feeling that if all you have is a hammer, everything is a nail. It’s nice that we finally have choices. Even in the trabecular bypass MIGS space that there are, at least, 2 options that can be used, and regardless of which one the surgeon is comfortable using, you’ll get fairly similar results. I think all of these, because they’re less invasive than, let’s say, trabeculectomies or external filtration or aqueous shunts, these are reasonable options to be considered.
Now in the U.S., the Hydrus is not approved for pseudophakes. The iStent is. The iStent infinite has achieved FDA approval, so it can be used in pseudophakic eyes, and I think it’s a reasonable device to use before one gets to the next step, whether that be canaloplasty or external filtration or suprachoroidal. I guess, that’s my overall take regarding this particular study. I can speak to this clinically, because I have used both. The adverse event rate was approximately 24% in iStent and 36% in Hydrus, and those included peripheral anterior synechiae (PAS) greater than 1 mm, iridodialysis, crystalline lens damage in phakic eyes.
I would say that, in my experience, you can see PAS formation in both of these devices. Now, in the Hydrus, I haven’t really seen it and majority of patients have an effect on the outcome pressure-wise, PAS has also been seen in the iStent infinite. Generally, you’re putting 3 devices in, and so if PAS blocks 1, you still have 2 to get into Schlemm’s canal. I don’t know how much of a difference that makes. I think the biggest thing I would say is in terms of the skill set to be able to implant them, they both have to be taken seriously. The iStent infinite is certainly, in my hands, and from what I’ve seen, is it’s less traumatic because the devices are so much smaller. You’re putting 3.
The Hydrus device is quite large, and you have to be very careful when you’re putting that in. One of the best pieces of advice I received from a colleague of mine, Dan Eisenberg, is to be four o’clock hours away from the insertion entry point in trabecular meshwork, so that the curvature and the arc is appropriate to be able to put the Hydrus device in. The other thing I’ve seen in referred patients is when the Hydrus is not properly implanted, it can create problems. When I do the Hydrus, I always use a gonio mirror that is disposable and enables me to see the distal location of the Hydrus device.
The Hydrus device is quite large, and if it looks like it’s well positioned proximally, it doesn’t mean it’s positioned in the trabecular meshwork distally, so you have to make sure you see it in the trabecular meshwork. It’s a very satisfying procedure when it’s done and it’s successful, but you have to check the position and be 100% sure you’re in Schlemm’s canal the entire way. If you lose it and it’s pointing down into the ciliary body or you lose it into Schwalbe’s line, that’s not where it needs to be. It needs to be removed and reinserted.
As far as iStent infinite, it requires 3 insertions, not 1, so you have to make sure that when you’re implanting it, you’re implanting it in the trabecular meshwork. The position of the surgeon is really important in terms of being able to implant it directly across from whichever part of the angle you’re implanting it to. That does mean rotating the microscope and moving your hand within the incision. The device can, if it’s pushed too hard, can be over-implanted, which means it will not cause a problem, but it won’t function, because it’s sitting in Schlemm’s canal. It’s not going through the trabecular meshwork and providing entry to the aqueous. It’s actually intracanulicular. If you push too hard, the device can bounce off the posterior wall, and then you’re tasked with rebating it to the trocar and then re-implanting it. That requires some skill set. You have to be careful when you’re implanting both of these for different reasons.
I do think that it’s important to take these devices seriously. I think the training is important. However, clearly, they both give us a lot of options at reducing medication that the patients need to take or, in some cases, eliminating medication. One of the most satisfying parts about this procedure with Hydrus is being able to put it in, put on a disposable gonio mirror, and actually see it across the entire length of it in the canal. Seeing the windows, seeing the proximal end, it’s very satisfying.
What’s very satisfying with the iStent infinite is when it’s implanted and you’re fortunate enough to see blood reflux, which can be amazing, patients can end up with a microhyphema, that’s telling you that you have quite a good connection. Not only is there quite a good connection, the patient’s intrascleral veins are functioning and one can anticipate that you’re going to get a reasonable or very good pressure response. They both are satisfying procedures, as a surgeon, to perform. They’re minimally invasive, but again, you have to take them seriously, and the training has to be good, and have to be committed to putting them properly.
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