Part 11 of 14 of “Adjusting the Faucet or Opening the Drain – Currently Available Methods to Treat the Plumbing Problem of Open Angle Glaucoma” | A San Gabriel Valley Optometric Society (SGVOS) Continuing Education Dinner Event – 2 hours CE | Featured Speaker: Dr. David Richardson, MD | April 12, 2017
So other angle based surgeries…
The first micro invasive surgical implant to be FDA-approved is the IStent®. For use with ocular hypertension, mild Open Angle Glaucoma—to be done with cataract surgery. And you can see, it’s pretty neat device— it’s this snorkel that is meant to be implanted through the trabecular meshwork, into the canal.
The problem is that it limits future surgeries. If you do this you can’t do canaloplasty or other procedures that require access to that area of the canal. And it’s damn expensive! I mean this device is the smallest FDA-approved surgical implant – ever. It’s made of titanium and per ounce this is the most valuable expensive thing you could ever purchase. I think that you know some rare man-made elements that you have to create in the Hadron Collider, maybe more expensive than this—but per ounce. But this is well-reimbursed. The implant itself is a thousand dollars and that’s about what the surgeon is paid for implanting one of these. So they become quite popular.
The question is do they work and here’s a video from Ike Ahmed, who is just a truly expert, expert surgeon and has had the ability to be involved in a lot of these new surgical procedures. Have done a lot in terms of, you know, figuring out how best to do these things and this is him performing the surgery and as with all of his surgeries it’s just elegant to watch. You can see him implant the stent and he makes everything look so easy but one of the things about this particular video which underscores the issue with the iStent® is – you’re going to see in this video, that he does not implant one. He does not implant two. He implants three of these in the eye. Now if you implant three of these in the eye you should get an effect. The problem here in the US (separate from Canada) is you’re only going to get paid for one and at a thousand dollars each good luck finding a surgery center that’s going eat the extra two thousand or patient who’s going to be willing to pay for the extra two thousand. You can see how this goes into the canal through the trabecular meshwork and I just love watching his videos. I can’t think of too many too many eye surgeons who don’t. His work is so nice. Anyway, so… his surgical technique—absolutely fantastic!
How about the results of the iStent®? Do they match his surgical technique? No they don’t. The one year result of the iStent®—cataract surgery alone is done the pressure is reduced by…. the percentage of patients who achieved a pressure lower than 22 mmHg? 50% – so half of the patients, just from cataract surgery alone, will achieve that pressure under 22 mmHg. How about if you put the iStent® in with cataract surgery? 72%. Okay— so yeah you do get more but the majority of the reduction there is from the cataract surgery. Say, “okay well you know that some of these drops can be pretty expensive right?” I mean we’ve all got patients who are saying, “doctor that drop that you prescribed me the Simbrinza, it’s $250 a month.” Well a year of Simbrinza®—and you know this is paid for itself. So maybe not so impressive when you’re looking at the difference between cataract surgery alone and cataract surgery plus the iStent® but taking a bigger picture it can be a useful option. But two years after surgery there’s no statistically significant difference between those who had cataract surgery alone and those who had cataract surgery plus the iStent®.
So it’s easy to put in, it’s currently paid for by insurance, but is it really going to give us a long-term benefit? Probably not.
So what other options are there, well just recently at the end of 2016, the FDA approved the Cypass® Microstent.
Now this is exciting because this is using an outflow shunting method that has not been available to us before. That is, it’s also like with the iStent®, only approved for those who are also having cataract surgery. The nice thing about this is because it uses a separate outflow it can be used even in patients who have had or may need to have other glaucoma surgeries.
I want to show you this this video here…so this is showing the outflow pathway, showing essentially both the pathway through the trabecular meshwork as well as through the through the uvea scleral outflow. You can see that this is an essentially a tube. But it’s a tube is designed in such a way that it can atraumatically sit in the supraciliary space. So you can see that right in the angle, above the ciliary body and shunt fluid into that space. And it’s a very quick procedure. Basically you make an incision, just like you would with cataract surgery. You fill the eye with viscoelastic … (I’m sure we don’t need to see all the details of this) and you have this injector. It’s placed into the angle and then simply inserted into the supraciliary space. And there it is…
So the question of course is how well does it work? So if we look at 2-year results (and we do have two year results on this), they looked at patients whose diurnal curve was between (i think it was) 18 mmHg or 6 mmHg. That’s right – 6 mmHg and 18 mmHg and 61.2% patients of the Cypass® maintained this range versus 43.5% with cataract surgery alone. So again, what you see here is that, cataract surgery alone does have a beneficial effect in treating glaucoma. So more however experience this range of diurnal curve with combined cataract surgery and Cypass®. if we look at the absolute pressure reduction 7 mmHg with a Cypass® versus 5.3 mmHg on average which cataract surgery – really doesn’t look that impressive, alright. Less than 2 mmHg but if you look at the percentage difference it was 32% and again what we’re going to find is that with all of these lower risk micro invasive surgeries we don’t necessarily have to think of just one. We could potentially think of building up on different surgeries using different outflow pathways in order to achieve a reduction that could potentially end up in the same range as trabeculectomy or glaucoma drainage devices but without the vision threatening complications. And if we look at the two-year results in terms of the percentage of patients who achieved a non-medicated pressure of 20mmHg or less… so 20mmHg or less without drops, 72.5% of patients for Cypass® achieve this versus almost 60% with cataract surgery alone. In terms of adverse events, there really weren’t that many when you look at the comparison of the combined Cypass® with cataract surgery versus cataract surgery alone, overall, quite similar. So it seems to be a pretty safe, safe device.
Xen® 45 Gel Stent
Also approved— at the end of 2016 by the FDA, the Xen® 45 Gel Stent. This is a chemically treated gelatin tube. It’s basically what it is – it’s a tube but it’s been designed so that the aqueous flow through it is restricted in such a way that it reduces the risk of hypotony. So, this is essentially an Ab-Interno method of trabeculectomy. You’re shunting the fluid into the subconjunctival space. So it still requires a bleb to achieve intraocular pressure lowering and as such it still has all of the potential complications or most if not all, that trabeculectomy would.
The issue with this is that although it shares many of the complications with Trabeculectomy and although it’s much faster and in some ways easier to do, it doesn’t seem to do quite as well as Trabeculectomy in terms of pressure reduction. So the average drop of 30% from 20.8% to 14.4% at 1 year – not quite as impressive as trabeculectomy. Three year results looked pretty good 40% reduction, 75% medication reduction, and about 5% of participants needed to go on to additional surgery, which is pretty typical for glaucoma surgeries. But as I said (was saying) earlier you have these issues of short and long term hypotony, potential for loss of vision—that’s not insignificant, right? 6.2 % long-term loss. So that’s on par with, really, trabeculectomy.
Cataract surgery – I’m not going to belabour on this point. You’ve seen already from the studies I showed earlier that cataract surgery alone can be effective with glaucoma. So for many of our patients who are kind of doing pretty well with their glaucoma – we’d like the pressure to be a little bit lower, they may be having some progression. If they’ve got cataracts or cataracts that are ready for surgery, and they’re not maxed out on medications, then cataract surgery alone, for many of these patients, is perfectly reasonable. The issue though is, if they are maxed out on medications and you perform cataract surgery and they have a pressure spike, which is not uncommon among glaucoma patients of cataract surgery, then what are you going to do? Then your only option is Diamox. So patients who are on max-tolerated medical therapy and need cataract surgery, we will generally consider combining the cataract surgery with one of these MIGS procedures. But if they’re not maxed out it’s perfectly reasonable to consider just cataract surgery alone in those who have mild to moderate glaucoma.
08.29.2018 NEWS UPDATE: Alcon announces voluntary global market withdrawal of CyPass Micro-Stent for surgical glaucoma | SOURCE: https://bit.ly/2wpGDHP
Currently Available Methods to Treat Open Angle Glaucoma Series:
- Currently Available Methods to Treat Open Angle Glaucoma
- Beta-blockers, Selective Alpha Adrenergic Agonist, CAIs
- Prostaglandin Analogs, Cholinergic Receptors Agonists, Fixed Combination Agents
- Carbonic Anhydrase Inhibitors (CAIs)
- Laser Trabeculoplasty
- Continuous Wave and Micropulse® Cyclophotocoagulation
- Trabeculectomy and Glaucoma Drainage Devices
- Ab-Externo Canaloplasty
- Ab-Interno Canaloplasty
- IStent®, Cypass® Microstent, Xen® 45 Gel Stent, Cataract Surgery
- Next-Generation Glaucoma Medications and Surgeries
- iStent Supra®, Hydrus™ Microstent, and InnFocus MicroShunt®
- Canaloplasty with Stegmann Canal Expander