Part 8 of 14 of “Adjusting the Faucet or Opening the Drain – Currently Available Methods to Treat the Plumbing Problem of Open Angle Glaucoma” | A San Gabriel Valley Optometric Society (SGVOS) Continuing Education Dinner Event – 2 hours CE | Featured Speaker: Dr. David Richardson, MD | April 12, 2017
Currently Available Incisional Treatments for Glaucoma
(Lower Risk Surgeries)
So this is where the newer, lower risk surgeries are really exciting. The question is, are the lower risk surgeries as effective as the higher risk, older penetrating surgeries? so we’re going to look at the Ab-Externo (from the outside) and the Ab-Interno.
Of the Ab-Externo, the main one is Canaloplasty. This is a develop— this is essentially a modification of a surgery that’s very commonly done in Europe, which is called Deep Sclerectomy or ViscoCanalostomy (this is another version of that). And they use it in Europe because it’s safer than Trabeculectomy. Well in the case of—when we’re talking of ViscoCanalostomy or Canaloplasty, these are non-penetrating. So you’re not actually creating a fistula from the anterior chamber into the subconjunctival space. So there’s no hole, no bleb… but they work well. So, you do lower the pressure, you have fewer drops in general, they’re safer than traditional surgeries, and this is key for our patients who like to be active: you, generally, do not have to adjust your lifestyle.
And so, showing you what Canaloplasty looks like here. You do—and this is just going to go through (sorry) the normal pathway of aqueous being produced by the axillary epithelium, going out through the trabecular meshwork but in the case of glaucoma patients there’s a blockage in either on the Trabecular Meshwork or the Schlemm’s canal…So with canaloplasty, you do create a partial thickness scleral flap; so it’s not a full thickness scleral flap. It’s a partial thickness. And a catheter-the world’s smallest catheter, it’s incredible little 250 micrometer diameter catheter is threaded through the canal, which is pretty neat to see. Once it’s through, you tie a suture to it and pull the suture back through the canal. Now why would you do that? The idea is as you’re pulling it back through the canal you’re actually injecting viscoelastic to dilate the canal. So it’s kind of like angioplasty for the eye. Now once you’ve pulled the suture back through you tie it to tighten the inner wall of the canal kind of like you tie a hoodie to bring it down and you can see that pulling down on the inner wall. Now what happens is you dilate the canal and you stent it open so you get better flow into the Schlemm’s canal and then out through the collector channel systems. Aha! But you have to have an open collector channel system, which there’s unfortunately no way to detect beforehand and this is going to be a theme through the rest of this talk.
So how does it work? Well it turns out it works pretty well, okay. And one study that looked at the two surgeries Trabeculectomy versus Canaloplasty there was not a significant difference between the final pressures: 13.4 with Trabeculectomy (and this is one year out) versus 12.3 (sorry) 13.4 with Canaloplasty (I correct myself) versus 12.3 with Trabeculectomy and mitomycin. So yes Trabeculectomy had a tendency to be lower but it wasn’t a statistically significant difference.
What was different importantly is the risks. Patients had better vision with Canaloplasty, they had lower risk of hypotony, they had no issues with blebs… I could go on. Anyway the three year results are quite good in terms of the reduction. So if Canaloplasty only there was a 34% mean IOP reduction from baseline and a 53% reduction in drop use. So not only did the pressure drop, but the number of drops that were required to keep that pressure dropped as well. If you combine Canaloplasty with phacoemulsification (so cataract surgery) it gets even better 42% mean intraocular pressure reduction. 81% mean reduction in drops and 90% (eighty-eight% of patients) were drop- free three years after surgery today without the risks of Trabeculectomy. So this is a really, really exciting procedure.
The doctor who developed Canaloplasty, Dr. Robert Stegmann in South Africa, is an absolute genius. I think this quote pretty much sums it up, “it’s vital to find a safer more predictable operation with preferably no complications at all (and he felt that) canaloplasty is the closest that (he) has ever come to that”. And that’s another point that I didn’t make earlier; with Trabeculectomy/Glaucoma Drainage Devices it there’s no coupling between surgeon skill and the outcome. You speak to experience glaucoma surgeons, they will tell you “I will finish what I think is a perfect Trabeculectomy and have no idea how this patients going to do because it’s so dependent upon the body’s healing response.” And that’s not the case with Canaloplasty.
Currently Available Methods to Treat Open Angle Glaucoma Series:
- Currently Available Methods to Treat Open Angle Glaucoma
- Beta-blockers, Selective Alpha Adrenergic Agonist, CAIs
- Prostaglandin Analogs, Cholinergic Receptors Agonists, Fixed Combination Agents
- Carbonic Anhydrase Inhibitors (CAIs)
- Laser Trabeculoplasty
- Continuous Wave and Micropulse® Cyclophotocoagulation
- Trabeculectomy and Glaucoma Drainage Devices
- Ab-Externo Canaloplasty
- Ab-Interno Canaloplasty
- IStent®, Cypass® Microstent, Xen® 45 Gel Stent, Cataract Surgery
- Next-Generation Glaucoma Medications and Surgeries
- iStent Supra®, Hydrus™ Microstent, and InnFocus MicroShunt®
- Canaloplasty with Stegmann Canal Expander