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Treatment Guidelines, ABiC

Procedure Guidelines

  • Following cataract surgery, inject Miostat into the anterior chamber, followed by a dispersive viscoelastic. Create a sideport incision for inserting the iTrack™ microcatheter approximately 1 1/2 clock hours away from the 3-o’clock (right eye) or 9-o’clock (left eye) position. Next, insert the primed iTrack™ microcatheter into the anterior chamber.
  • Entering at the temporal location, create a small horizontal incision approximately 1-mm wide in the trabecular meshwork.
  • Using MST retina forceps, feed the iTrack™ microcatheter into Schlemm’s canal and align it flush to the trabecular meshwork. As the tip of the iTrack™ is advanced 360° to the initial incision site, follow its progress by observing the position of the red light.
  • Slowly withdraw the iTrack™ microcatheter while steadily injecting viscoelastic. Once this step is complete, remove all dispersive viscoelastic from the anterior chamber.
  • Unlike with traditional Canaloplasty, a tensioning suture is not placed into Schlemm’s canal during viscodilation.

Patient Selection

ABiC™ is indicated for the reduction of elevated IOP in patients with open-angle glaucoma, including those with ocular surface disease and individuals who cannot tolerate anti-glaucoma medications. ABiC™ is also suitable for the following:

  • Pigmentary glaucoma (PG)
  • Pseudoexfoliation Glaucoma (PXF)
  • Ocular Hypertension
  • Post-SLT eyes
  • Eyes that have received a single session of low-powered ALT
  • Patients with previous failed trabeculectomy or tube surgery
  • OAG with narrow but not occludable angles after laser iridectomy
  • (Note: Once a surgeon has gained the necessary experience, ABiC™ can also be performed on patients who have previously undergone trabeculectomy or tube surgery.)

ABiC™ is contraindicated for the following:

  • Neovascular glaucoma
  • Multiple argon laser trabeculoplasty (ALT): Patients who have undergone more than one ALT procedure
  • Chronic uveitis
  • OAG with narrow angle (Note: unless canaloplasty and phacoemulsification are scheduled at the same time)
  • Narrow inlet with plateau iris

Clinical Tips and Pearls

The following guidance has been provided by ABiC™ pioneer Dr. Mahmoud A. Khaimi, MD (Dean McGee Eye Institute, University of Oklahoma)

Proper paracentesisis placement

Proper trajectory of the paracentesisis essential. I recommend surgeons to create their paracentesis oriented toward the goniotomy site. Additionally, if the paracentesis is made too superficial, the iTrackTM catheter will not easily direct toward the goniotomy site.

Making the Goniotomy

I recommend using a 27-gauge . Inch needle to very slightly score the anterior portion of the trabecular meshwork. I start by using the needle in a left to right motion, then proceed to pulling the trabecular meshwork downward to create the otomy. A major pitfall at this portion of the procedure results from the misconception one needs to use a very sharp instrument or dig deep into the meshwork to expose the canal. The canal is actually very superficial and deep penetration can result in additional bleeding and an opening into the scleral wall, resulting in obstruction.

Successful Canal Intubation

Following insertion into the anterior chamber, MST 23g Micro-Holding Forceps (Microsurgical Technology) can be used to grasp the iTrack™ at an oblique angle 2-3 mm from the distal end. These curved forceps provide an easy to use and stable tool for accurate insertion of the iTrackTM into Schlemm’s canal through the otomy site at a 15. angle. The serrations of the 23g MST Micro-Holding Forceps also ensure a firm grasp of the probe with reliable tactile feedback for advancement into the canal. A loose grip of the probe can result in sliding of the forceps down the catheter, falsely emulating an obstruction when the probe simply isn’t advancing. This is particularly important in difficult intubations where proper manipulation of the probe, close to the goniotomy site, can result in a successful intubation. The iTrackTM should be placed flush to the adjacent trabecular meshwork, which can be used as a ‘runway’ to advance the probe.

Viscodilation

The illuminated red-lit tip of the iTrack™ can be followed as it is advanced 360 degrees. Synchronization with your surgical scrub is essential during this process. Once both the surgeon and surgical tech are comfortable, I recommend 30-40 clicks during withdrawal.

Postoperative Management

Another important thing to note, is an increase in IOP one to four weeks following surgery is normal. Drainage function returns at different times for different people depending on the dynamics of drainage system. As a result of this, I typically will not restart glaucoma drops if it is safe to do so. Based on my experience, pressures will go down naturally after three to six weeks. For patients with a significant postoperative spike, I typically put on one to two drops and have them come back in three to four weeks, discontinuing the drops at that time if the IOP decreased. The other aspect of postoperative management pertains to steroid use. My preferred regimen is Lotemax four times a day for three days, then once a day for three days. ABiC™ is a minimally invasive procedure that results in minimal inflammation, therefore a longer course of steroids is not indicated.

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