We have found placing the XEN® Gel Stent either supra-Tenon’s or subconjunctival when possible results in further IOP-lowering. This video demonstrates pearls to achieve this placement, which involves tilting up of the needle as it exits sclera to ensure that it gets through Tenon’s and under conjunctiva as much as possible.
Surgeon: Dr. Ike K. Ahmed, University of Toronto, Canada
This is a combined phaco-Xen case. We’ll start with a mitomycin injection on a 30-gauge needle here, being placed 6 to 8 millimeters back from the limbus, injecting an intra-Tenon’s dose of mitomycin, small dose of 0.1 CC, 0.2 milligrams per CC, in terms of concentration, and then having the patient look down, while rotating a wet Q-Tip, a moistened Q-Tip, to keep that mitomycin back away from the limbus. The goal here of course is to create a more posterior bleb, and the area of application is in the superonasal quadrant. It will be the area where the Xen will be intended to be implanted. Having the patient look down again, rotating the Q-Tip here, to keep the mitomycin away. Usually wait about a minute or so, prior to making the incisions. Mitomycin binds fairly quickly, so there’s really very little concern about entering the eye, although we do irrigate the surface of the eye, to ensure there’s no free mitomycin that may have leaked onto the surface of the eye, prior to making incisions. The main incision is made temporal in all cases. This will be used both for the phaco, as well as for the Xen implantation as well. Once the cataract and lens implantation has been performed, we’ll leave the OVD in the eye, we’ll inject in some Healon GV. I find it keeps the AC well formed. Here’s the Xen implant in that 27-gauge needle. We’ll pass it to the main incision, lifting up slightly with a pair of forceps, and I want to place the needle just toward 12:00, so it’ll basically enter the angle at the 12:00 position, aiming to the superonasal quadrant, using the gonio mirror. Here I want to basically place the needle just anterior to the trabecular meshwork. This avoids reflux bleeding from the canal, should we enter it. So going anteriorly does help to avoid that. We then use a Vera hook for traction, pushing forward, trying to aim for a long tract. We can always end up going shorter if we need to, but it’s better to go long at first. And trying to emerge 2.5 to 3 millimeters back from the limbus. Here we’re going tangentially, of course, because we’ve entered the eye at the temporal position. And then watch — I really try to get this needle pointing up, really touching conj. It almost looks like it’s gonna perforate. It really doesn’t, because we have the tissue here on expansion with the mitomycin. Look how clear the needle is shown under the conjunctiva. I really want to get that needle through Tenon’s, just under conjunctiva. Really pushing up superficially. Rotating the needle to really get it tenting up the conjunctiva. So I know I’m through Tenon’s and away from any kind of deep Tenon’s placement. There’s the deployment, slide it past and forward, needle has passed — retracted into the cannula, after the implant has passed forward. And now once the needle is into the cannula, we relax our hand here for a second. Take a pause, and then pull back without flicking the cannula to avoid retraction of the device into the eye. Sometimes a small little heme here. At the exit site of the implantation. Putting some pressure on for about 30 seconds here really helps to provide hemostasis here, to prevent any expansion of that hematoma, and really, this is very self-limiting in most cases. The gonio mirror now shows the implantation in the angle, nicely positioned anterior to the TM. We see about a millimeter in the anterior chamber. Well positioned here. This is exactly what we like to see for the intraocular portion of Xen implantation. You’ve got a couple millimeters of the implant in subconj space. I like to make sure the implant is free and mobile. You see how free and mobile it is? It’s not stuck down. It’s very easily maneuverable by the cannula. And we’ll basically milk it a bit, to ensure we have a nice placement here again. And we know this is likely to be superficial, because of how free and mobile it is. We’ll now inject BSS in the anterior chamber, removing the Healon GV while we do that, and watch the bleb form here. This is priming the implant. And you’ll see very quickly how widely the bleb forms. This tells us we’re quite superficial. The fluid is all going more subconj. And the implant is actually sitting up, it’s rising up, sitting away from the sclera. And this is an ideal position of the implant, telling us that we’re superficial, and placement is not deep. Because the implant actually is sitting above Tenon’s, and is actually under conjunctiva. It’s actually rising up above the sclera. It’s not a problem, really, to have it point up a little bit like that. I think it’s ideal, in fact. And you can see how wide the extension of that fluid goes. Again, telling us that we have more of a subconj rather than a sub-Tenon’s or inter-Tenon’s placement. In fact, you can look at the conjunctiva, and you can see how translucent it is. You can see the conj clearly. Underneath, you see the Tenon’s and sclera, telling us that we separated conj from Tenon’s. By this very, very thin elevated bleb here with fluid underneath it. The intraocular pressure is quite good. Typically because of the control flow. And we have a well formed wide bleb at the end of the case, which is ideal in these scenarios.
October 31, 2019