Dear Dr Richardson,
As an advancing OAG patient, I have for some time now been interested in the canaloplasty procedure. In Australia, however, where I live, no glaucoma specialist is yet performing this surgery. Of course, the overriding reason for my interest is with this surgery’s safety profile over that of traditional filtering surgery (particularly in my case with lagophthalmos).
One concern expressed by an ophthalmologist down here is with the tensioning suture being left indefinitely in place in the canal. I gather that there have not been any concerns to date in this regard? Another concern I have heard mentioned is with the efficacy of the canaloplasty with NTG patients, the ones who were not formerly NTG patients but had advanced to such a stage following successful, at the time, SLT interventions with various ongoing topical medications, all of which were no longer effective with the newly acquired NTG.
Lastly, I am wondering if trials were ever done with a canaloplasty type procedure where the tensioning suture were excluded. If a circumnavigation of Schlemm’s canal were done with the microcatheter (including viscodilation) to help unroof the canal, with a soon after postoperative ALT or SLT of the trabecular meshwork, then two questionable sites would be (virtually) concurrently addressed. Without a prompt laser trabeculoplasty being done subsequent to the above unroofing of the canal, would it not be possible, then, that the canal could eventually re-collapse with an inefficacious pinocytosis of aqueous percolating through the meshwork? Conversely, in the absence of an almost simultaneous canal dilation, would this not be the reason that ALT and SLT have not always had good long term outcomes? All in all, with both sites concurrently targeted, perhaps the tensioning suture may not be required.
Many thanks in advance.
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You have a number of good questions, not all of which have answers that are known.
- With regard to the Prolene suture, this material has a very good track record as it has been used as intraocular lens haptic material for decades with exceedingly rare complications associated with it.
- NTG is a challenge with any treatment (medical or surgical). I have treated NTG patients with canaloplasty but generally warn them that canaloplasty alone will not eliminate their need for drops. Trabeculectomy is more likely than canaloplasty to reach the target IOP in someone with NTG or advanced glaucoma, but as you know, that comes with a price paid in risk and lifestyle limitations.
- The suture is needed for full effect. All experienced canaloplasty surgeons will tell you that IOP lowering effect is diminished in patients in whom they could not fully catheterize and place the Prolene suture. In my experience placement of the stent (suture) adds an additional 2-3mmHg IOP lowering.
- Finally, with regard to SLT and ALT, no one really knows how these procedures work so your guess is as good as anyone elses.
I know it is a very long way to travel, but if your ophthalmologist feels your angle structure is compatible with canaloplasty and you wished to consider traveling out to see me for canaloplasty surgery I’d be happy to review your eye records and test reports before you finalized any plans. The main issues faced by those who travel to see me are coordination of adequate length of stay in the USA as well as finding a surgeon back home who would be willing to continue your care after surgery.
David Richardson, MD
Date: July 22, 2014