HydrusTM vs iStent® Trabecular MicroBypass |
Which Performed Better?
I’m Dr. David Richardson, a cataract and glaucoma surgeon in Southern California I just returned from the American glaucoma Society annual meeting in San Francisco where there were a number of interesting presentations.
I have already presented a video on one of the findings presented by Dr. Ike Ahmed, which you can find in a separate video by me. [Read here: What’s Exciting About Bimatoprost SR Glaucoma Drug Implant].
What I’d like to present today was a presentation that was given by Dr. Thomas Samuelson. He presented the compare trial results at 24 months, which looked at two different minimally invasive glaucoma surgeries— the Hydrus™ and the iStent®. So, let’s take a look at these study results.
Now both the Hydrus™ and the iStent® are what are considered to be Trabecular MicroBypass Devices. They actually shunt aqueous fluid from the anterior chamber through the trabecular meshwork into Schlemm’s canal.
Now, the iStent® has been around for a few years and has been embraced by cataract surgeons as a quick simple way to lower pressure at the time of cataract surgery. The problem with most minimally invasive glaucoma surgery studies, to date, is that they’ve almost all been in conjunction with cataract surgery. The problem there is that we know that cataract surgery alone can reduce pressure. So, when you combine something with cataract surgery, the question that remains is, “well how much of the pressure reduction that occurred was really from the device and how much was from the cataract surgery itself?”
There are a few studies, for the most part pretty small, that look at MIGS benefit in those who have not also had cataract surgery at the same time but those studies are pretty small. And what we really would like to know is, which of the bypass stents is the most effective. So the compare trial actually took a look at comparing two different MicroBypass stents against each other without cataract surgery being performed at the same time.
Now, I’ll talk about the Hydrus™ implant in more detail in a separate video but just briefly, the Hydrus™ is an eyelash-sized implant that goes through the trabecular meshwork into the canal (and unlike the iStent®, which is basically just a little snorkel that pops through the trabecular meshwork and opens into the canal), the Hydrus™ actually stents open the canal and for a pretty significant portion of the canal, almost a quarter of the canal is open, so what we call three o’clock hours, so one would think that with that stenting open of the canal that one would achieve an additional pressure reduction or ability to get off of medications compared to say iStent®.
Now, I suppose to be fair, what the compare study did was actually compare the Hydrus™ (1 Hydrus™ Trabecular MicroBypass stent) to 2 iStents.
So what were the results at 24 months? Those who had the Hydrus™ Trabecular MicroBypass stent were more likely to be off all medications than those who had to 2 iStents. How much more likely twice? Twice as likely. So, 37% of those who had the Hydrus™ implant were off all medications compared to just under 19% of those who had 2 iStents.
So, we can’t expect everybody to be off medications. And it’s also worth noting that…I didn’t mention it earlier but…this study only included those who had mild to moderate glaucoma. It’s not yet felt that minimally invasive glaucoma surgery is appropriate for those with more advanced glaucoma, which require a significantly lower target pressures. But how about for those who were still on medications? Did they at least have to take fewer medications? And the answer is yes. So, the Hydrus™ again (here) performed better than those who had 2 iStents. How much better? On average, medication use was decreased by about 50% in those who have the Hydrus™ Trabecular MicroBypass stent versus about 30% reduction in those who had 2 iStent Trabecular MicroBypass stents.
How about percent decrease in pressure? Because ultimately that’s what we’re looking for is getting the intraocular pressure lower in most people who are going on to surgery. One way to look at that is to ask the question, “Well, what percentage of those in the study achieved a 20% reduction in pressure?”
In the Hydrus™ group, approximately 60% achieved a reduction of 20% in their intraocular pressures compared to prior to surgery. In the 2 iStent® group, approximately 40% of the patients achieved a 20% reduction in intraocular pressure compared to preoperative pressure values.
So, in addition to the seeming superiority of the Hydrus™ stent over the iStent®, there are a couple of interesting things about this study. The first is that it was comparing the Hydrus™ stent to the older version of the iStent®, which for the most part surgeons are only putting one in. Now, there is a newer iStent®, the iStent inject®. that it actually comes preloaded with two stents so it seems quite clear that placing one Hydrus™ stent should be far superior to placing one of the older style iStent®, given that comparing the Hydrus™ to two of the older style iStent®, the Hydrus™ came out superior. What we don’t know is whether or not the Hydrus™ would have a similar superiority compared to 2 the iStent inject®.
I’m not sure that study is going to be done simply because these studies are expensive, takes time, and you know with the development cycles you end up kind of chasing the version of Stent. But in any case this study has a couple of very important outcomes. One is that even without cataract surgery both the Hydrus™ and at least two iStents were capable of bringing down the pressure in someone with mild to moderate glaucoma.
Minimally invasive glaucoma surgeries such as placement of the iStent® or the Hydrus™ have generally proven to be quite safe in the studies that have been presented today with very, very low risk for loss of vision or other vision threatening complications
Given the similar safety profile it certainly appears from this study that the Hydrus™ is the clear winner but can we expect most surgeons to switch over from the iStent® to the Hydrus? Probably not and the reasons for that are multifactorial. One of which is that the Hydrus™ is a larger stent. It is a larger stent, it is more challenging to insert. The iStent® is rather quick straightforward and easy to insert. And as this study showed, as well as par studies, it does provide an effect. Perhaps not everybody needs the effect that could be achieved by the Hydrus. And so there will continue to be a role for the Glaukos IStent® whether it’s the version 1 or the version 2 which is the iStent inject®.
Additionally, this presentation was given at the American Glaucoma Society meeting and as a specialty meeting was only attended by glaucoma surgeons. A large percentage of those who implant the Trabecular MicroBypass stents are actually cataract surgeons. So it’ll take some time for these results to get out to cataract surgeons and there will be a number of surgeons who will wait for the paper itself to be published and don’t make changes just from a presentation, which is reasonable because the data is only presented in summary form and it’s not possible to go through it in the kind of detail that you can once a paper is published in a journal.
So, in any case I found this to be one of the more exciting presentations at the annual meeting of the American glaucoma Society in San Francisco March 2019 and I believe it will impact the way I practice minimally invasive glaucoma surgery but I will also be waiting for the published results to make the final determination of that.
I hope you found this informative. Many of the papers that are given at these specialty meetings can be quite esoteric and not of great interest to the general public or those with conditions such as glaucoma. Given that there are now multiple minimally invasive glaucoma surgical options and that this was the first randomized controlled perspective trial to actually compare two of the Trabecular MicroBypass stent options, I felt that this was a valuable study worthy of comparison.
I hope you agree.
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