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November 5, 2018
QUESTION [from an eye surgeon]:
I’m planning to start trying iTrack, after using iStents for 4 years now. Any advice on the good, bad, and ugly with this type of canaloplasty?
Thanks,
via Email
ANSWER:
When it comes to canaloplasty, I’m a bit of an “old dog” in that I still prefer the Ab-Externo technique as I primarily treat moderate to severe glaucoma in my practice and need all four IOP lowering elements of the surgery: dilation and stenting of the canal, and trans-scleral percolation into both the suprachoroidal space and subconjunctival space. That being said, I’ve been using Ab-Interno canaloplasty with the Ellex iTrack microcatheter more frequently as I’ve been impressed with how easy and effective it has been in my patients with mild to moderate glaucoma. I’ve even recently used it in patients with advanced glaucoma (who for other reasons were not candidates for ab-externo procedures).
My experience is that when combined with cataract surgery it’s about as effective as the other available (and previously available) MIGS options: an average of 1-3 mmHg IOP reduction beyond what cataract surgery alone would be expected to do. Where ABiC seems to shine is in the phakic or pseudophakic patients. It’s not tied to cataract surgery as with other MIGS procedures as the code was approved prior to MIGS existing.
As an important aside, it’s worth noting that the code for ABiC (66174, canaloplasty without stent) can be used with all forms of “primary or chronic open angle glaucoma” (mild, moderate, or severe) and is payable regardless of phakic status. For those who are already comfortable with the iStent but would like to offer their pseudophakic patients a MIGS option (for which they won’t be on the financial hook). ABiC is a great option. Medicare and most commercial insurances (payment from Blue Cross varies by state) will pay for the procedure. Indeed, this is the route I generally recommend for those considering ABiC. We all have patients who have already had cataract surgery but would likely benefit from MIGS. Ab-Interno canaloplasty is a great option for these patients.
Given that my experience is anecdotal, I’ve copied the results section from a recently published study by Mark Gallardo, Richard Supnet, and Ike Ahmed:
“The study included 75 eyes of 68 patients (mean age: 73.7±9.9 years) with a mean base-line IOP of 20.4±4.7 mmHg on 2.8±0.9 medications, which reduced to 13.3±1.9 mmHg (n=73) on 1.1±1.1 medications at 12 months postoperative (both P,0.0001). At 12 months, 40% of eyes were medication free. In the ABiC/phacoemulsification subgroup (n=34 eyes), the mean IOP and medication use decreased from 19.4±3.7 mmHg on 2.6±1.0 medications preoperatively to 13.0±1.8 mmHg on 0.8±0.2 medications at 12 months (both P,0.001). In the stand-alone ABiC subgroup (n=41), the mean IOP and medication use decreased from 21.2±5.3 mmHg on 3.0±0.7 medications preoperatively to 13.7±1.9 mmHg on 1.3±1.1 medications at 12 months (P=0.001 and ,0.001, respectively). No serious adverse events were recorded.”
No doubt there will be surgeons (many of whose opinion I greatly respect) who currently see no benefit to ABiC over GATT. With regard to the use of GATT, however, I strongly disagree. When the Ab-Externo form of trabeculotomy was initially studied decades ago it was given up because although it had an impressive initial effect, it eventually failed in adults. In peds the trabecular meshwork has a congenital obstruction so it works in that population. However, in adults the trabecular leaflets tend to scar down over time potentially worsening the outflow issue beyond pre-trabeculotomy. Thus, innovations such as the Trabectome and Kahook Dual Blade (KDB) were developed, the purpose of which is to remove the leaflets left by GATT that can obstruct outflow over time.
Even Trabectome and KDB, however, suffer from destruction of the trabecular meshwork. There is growing evidence that the trabecular meshwork is far from just a drainage grate and should be preserved if possible. Indeed, there is an impressive amount of work from Murray Johnstone demonstrating dynamic pulsatile flow (TM as pump) with direct connections via cylindrical attachments to collector channel flaps that act to open and close access to the collector channel system. Removal of the TM could potentially result in the flaps obstructing the collector channel openings (which may be one reason other than scarring of the trabecular leaflets that trabeculotomy eventually seems to fail in adults). Additionally, the elegant work of Darryl R. Overby has demonstrated a complex system of mechanosensory regulation of outflow that is dependent on the trabecular meshwork. Finally, there are multiple new pharmaceutical agents (one already available: Rhopressa) that would be unlikely to have any beneficial effect if the trabecular meshwork has been destroyed. Why eliminate an entire class (or future classes) of TM-dependent treatment options unless there are no other reasonable options?
Warm regards,
David Richardson, MD
Patient-Focused Ophthalmologist
San Marino Eye
2020 Huntington Drive
San Marino, CA 91108
626.289.7856
Patient-Focused Websites:
New-Glaucoma-Treatments.com
About-Eyes.com
Posted in: Canaloplasty, Canaloplasty and Other Surgeries, Canaloplasty and Recovery, Canaloplasty Cost, Canaloplasty Safety and Efficacy
