This video demonstrates the surgical technique of implanting an InnFocus Glaucoma MicroShunt. With a unique biocompatible SIBS material and a flow restrictor 70um lumen, this device appears to be one of the most potent glaucoma procedures while maintaining an improved safety profile compared to traditional approaches.
Surgeon: Dr. Ike K. Ahmed, University of Toronto, Canada
This video describes implantation of the InnFocus microshunt, and we’ll start by making a conjunctival peritomy in the superior limbus here. This should be approximately 5 to 6 millimeters in length, to allow for adequate exposure of the conjunctiva, as we’ll see later on in the video here, to allow for adequate placement of the device. Tenon’s insertion is cut and disinserted, as we see. The insertion is about 2 millimeters back from the limbus, and it’s important to cut Tenon’s here, undermined, overlying the episclera, and be sure to release Tenon’s, and raise the Tenon’s and conjunctival flap posteriorly. The Westcott scissors are going to be used to cut that insertion point, and then blunt dissection is used posteriorly in three different directions here. Left, right, and posteriorly here. The device is in total length 8.5 millimeters, and so we do need to make sure we have a good posterior dissection. Making sure we’ve released any attachments from Tenon’s onto the episclera. And the blunt Westcotts are going to be used to undermine and ensure we have a nice raised flap. You can see again we’re mobilizing the flap, making sure we have a good raised flap here. A bit of lidocaine injection here will help for analgesia. Endocautery is used at the limbus and episclera and sclera. In preparation of the scleral dissection here, using a 23-gauge tapered pencil cautery. We now will use 3 LASIK sponges that have been soaked in mitomycin C, 0.2 milligrams per CC. These are large Merocel sponges here, placed here under the conjunctiva and Tenon’s flap here, and these three sponges will allow for a broad application of mitomycin C, as we can see here, into the area where the intended bleb will form. We then take a 3 millimeter marker here, and we’ll mark from the limbus here. As you’ll see, we have the surgical limbus visualized here. Anterior and posterior limbus. The marker is at the anterior limbus here, and we see now the 3 millimeter point here, which will start the dissection here. We will then use a 1 millimeter microknife here. Note the bevel of this knife here creates a 2 millimeter tunnel from the tip of this knife to where the bevel ends, and therefore this tunnel will be essentially 1 millimeter wide by 2 millimeters long. Where we want to end up here is basically at the level of the scleral spur, which is where the entry point will be in the anterior chamber shortly. And therefore, going 3 millimeters back from the limbus approximately is where this point will be. Alternatively, one can basically mark from the scleral spur 2 millimeters back and dissect anteriorly to be sure of adequate length. Next, 25-gauge needle here is used, bent at the hub here. Basically retracing the path of that 1 millimeter blade. Reaching the spur, as we see here. Once we reach the spur, we dimple down to create an iris plane entry into the anterior chamber. This is critical to turn the blade down here. So we’re entering at the iris plane here, to avoid anterior placement of the implant in close proximity to the cornea. And by doing this, we now create an implant that will be placed just at the iris plane. So that change of direction is very important. Here is the IMS implant here. We see the fin here that’s being held by the forceps. The implant itself is 8.5 millimeters long. 4.5 proximal, and 3.5 distal to the fin. By choking up on the implant, we place the implant bevel-up. Through the tunnel here, slowly advancing this forward, and we’ll see the tip enter the anterior chamber. The fin basically then is occupied nicely, in a relatively self-sealing manner, into that scleral tunnel that was created with that 1 millimeter knife. And there we see the entry point here at the spur, entering into the anterior chamber, and again, ideally at the level of the iris plane. Using a thin walled, 23-gauge cannula, blunt cannula, we’ll inject BSS into the eye here. Essentially to check for patency. By doing this, we see a little bit of air bubble here emerge from the proximal end of the implant, and once we inject BSS into the eye, we lift the implant up, we notice here the 70 micron lumen here, and we see the BSS here, emanating from that lumen. The width of the device, by the way, external diameter 350 microns, and the lumen diameter is 70 microns. The implant then is placed very carefully under the conjunctiva. And under Tenon’s as well. Very important here. We lift up the Tenon’s here, so the implant lies just on the sclera, the bare sclera here, avoiding the implant from being embedded into the Tenon’s layer. We will then be sure that we have good placement here, without any twisting of the implant here, and then we will pull both conjunctiva and Tenon’s anteriorly. Again, critical pointer, to avoid Tenon’s from gathering at the distal end of the tip. We want to ensure we have adequate position of the tip under Tenon’s layer. To facilitate this, we’re actually gonna close Tenon’s and conjunctiva in two separate closures here. Here we’re using 9-0 vicryl on a specialized blunt spatula needle here. Allowing us to place Tenon’s here anteriorly at the insertion here. Again, ensuring and avoiding it from retracting here, potentially then occluding and gathering at the distal end of the implant. We will then close the conjunctiva here. Typically using here 9-0 vicryl again. Here placed here in two wing positions here. Making sure that we have a nice taut closure. The cautery, which has been applied at the limbus, will help for watertight closure, and you’ll see here, we’ll also use a horizontal mattress here, placed at the limbus. One of the advantages of this implant here is a nice posterior drainage point, into the area where the mitomycin has been applied. And therefore, we avoid the anterior blebs and anterior potential flow, and therefore wound leaks are quite rare with this implant. The posterior nature of the bleb, of course, is ideal, and away from the more active replicating cells of the limbus. Here we’re using a surgical gonio lens to evaluate the position of the device again. Ideally that’s a level of the spur just anterior to the iris. And here we see a nice position of the implant here, parallel to the iris. Just a little BSS here shows a nicely formed, well pressurized eye here. 70 micron lumen, 8.5 millimeter length of the implant. Avoids hypotony, and we have a nice sized bleb here, with pressures that typically will end up being in the high single digits in the early postoperative period.
November 18, 2019
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It’s wonder, educative, interesting. Should be known.