Gonioscopy-assisted transluminal trabeculotomy
This is an example of how we perform gonioscopy assisted transluminal trabeculotomy (GATT) at the University of Iowa. GATT is an ab interno 360 degree trabeculotomy. It is performed by making a 1-2 clock hour goniotomy and cannulating the canal of schlemm followed by a 360 degree trabeculotomy.
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Transcript
Here we have our first gonioscopy-assisted transluminal trabeculotomy (GATT) at the University of Iowa.
Here we are making an oblique paracentesis directed toward the nasal angle. This is followed by intracameral injection of Miostat to bring down the pupil along with viscoelastic to deepen the chamber and expose the angle structures. We use a ring stabilizer with a 2.2mm diamond keratome to make a temporal incision. Then the patient's head is rotated away from the surgeon to allow gonioscopic visualization of the angle structures. Here we use that gonioprism to visualize the angle structures.
Next, we use a 20 gauge MVR blade to approach the nasal angle. We enter first with the MVR blade before placing the gonioprism to ensure the proper trajectory. We then carry this across and focus on the nasal angle structures. We use the MVR blade to create a 1-2 clock hour goniotomy nasally. You can see that there is a good reflux of blood during this step through Schlemms canal, indicating that we have incised the proper area. You can see here my assistant handing me the Ellex iTrack microcatheter system, which has a lighted probe which you can set to illuminate intermittently to let you know where it is at all times. Here I am grasping that catheter with a microtying forcep and directing it towards Schlemms canal into that goniotomy and ultimately into Schlemms canal. You can see it enter there. Then once we have confirmed proper placement you can begin to pass this around through Schlemms canal. I am beginning to advance it here using the same micrograsping instrument. As I am moving it forward and advancing it forward, you can begin to see that illuminated probe within Schlemms canal through the sclera, ensuring where this is at all times. My assistant says, "Where is that again?" So we turn off the lights and one can see it very nicely here again, confirming we are in the correct space. Here we move forward and ensure that the microcatheter is passed all the way around and approaching that goniotomy cleft we originally made. So we passed the catheter 360 degrees. Here we are using viscoelastic to remove any heme to expose the terminal bulb of the microcatheter to facilitate us being able to grasp it. We are using that same micrograsper to reach across the anterior chamber and grab the terminal bulb within the goniotomy cleft. We then direct this toward the center of the anterior chamber. At this point we take a tying forcep and grasp the other end and begin to pull on both ends of the catheter, lysing that through the tissue for 360 degrees. One can see there is a good reflux of blood, which in this case is good because it indicates that we have lysed the trabecular meshwork and that there is blood refluxing from the episcleral veins into Schlemms canal.
Here we take our standard coaxial irrigation/aspiration tip to irrigate out the viscoelastic and heme. This can take some time. Here we are patient and do our best to get as much blood as possible. Once we are nearing completion, I am telling my assistant to get ready with the BSS cannula. I exit here and quickly retrieve the BSS on a 27 gauge cannula. I am hydrating my main wound as quickly as I can to try to raise the intraocular pressure. As long as the pressure is less than episcleral venous pressure, there will continue to be an accumulation of blood. Here I am hydrating the paracentesis as well. Once the eye is at a physiologic pressure and my main wound and paracentesis are fairly tight, I continue to irrigate for some time to evacuate the blood. And in the end, we leave the intraocular pressure slightly high in the upper teens to low twenties.
