So, How Long Has Canaloplasty Been Around?
One of the first attempts at creating a successful non-penetrating glaucoma surgery was reported by Dr. J. E. Cairns in 1968. Dr. Cairns wished to avoid the complications of penetrating surgery. Additionally, he felt that it was “unnecessary and unphysiologic to create a bypass to eliminate the activity, therefore, of the collector channels from the Canal of Schlemm.[1]” In other words, he wished to maintain as much of the eye’s natural drainage function as possible.
Because it was felt that the main restriction to fluid exiting the eye was located at the trabecular meshwork[2] Dr. Cairns’ developed a glaucoma surgery which was intended to cut out a portion of the trabecular meshwork. Removing a section of the trabecular meshwork created an opening in the Canal of Schlemm through which aqueous could pass unobstructed into the collector channel system and out of the eye. He specifically wished to restore the integrity of the wall of the eye (sclera) by suturing it “firmly back into place, the intention being to secure a watertight union.”
What did Dr. Cairns’ call this non-penetrating glaucoma surgery? Because the main purpose of this glaucoma surgery was to create an opening in the Canal of Schlemm, the surgery could easily have been called canalostomy. However, because his technique involved removing “a short length of the Canal of Schlemm, with its trabecular adnexae, thus leaving two cut ends opening directly into aqueous humor, with no trabecular tissue remaining as a barrier at that point,” he chose instead to call this glaucoma surgery “trabeculectomy” as a section of the trabecular meshwork (”trabecul”) was removed (”ectomy”).
What happened? Despite his best attempts, of the 17 cases first reported in 1968 “in six cases a bleb appeared. These may be regarded as failures in that the effect intended was not produced.[3]” [emphasis is mine] Additionally, it turned out that without a method of keeping the Canal of Schlemm open it eventually scarred down. It was soon noted that the surgical “failures” that developed blebs were the patients whose intraocular pressures (IOPs) were best controlled after surgery. These failed attempts at creating a non-penetrating glaucoma surgery were, however, experiencing far fewer complications than patients who had received the other penetrating surgeries of the day. So in essence the most common glaucoma surgery performed today is a direct result of a failed attempt to create a non-penetrating glaucoma surgery.
Dr. Cairns may not have been successful in his attempt to create a truly non-penetrating glaucoma surgery, but the quest for a safer, effective surgical method of controlling glaucoma has continued. One of the modern pioneers of non-penetrating glaucoma surgery is Dr. Robert Stegmann of South Africa. Two decades ago he conceived of the idea of not only creating a canalostomy, but of dilating it with a surgical gel called a viscoelastic. He called this procedure “viscocanalostomy”.[4]
It was Dr. Stegmann’s hope that by dilating the canal he could overcome the problem of stenosis (scarring down) of the opening that led to the failure of Dr. Cairns’ original attempts at non-penetrating glaucoma surgery. Dr. Stegmann’s surgery did successfully lower IOP (though not as much as trabeculectomy). An added benefit was its reduced risks compared to penetrating surgeries such as trabeculectomy.
A decade later Dr. Stegmann improved upon the success of viscocanalostomy by using a microcatheter to thread a suture around the canal. He then tightened the suture to keep the canal open in a manner similar to how cardiac stents keep blood vessels open during angioplasty. He called this procedure “canaloplasty”. In 2008 the FDA approved canaloplasty for use in the United States.
So how long has canaloplasty been around? Since 2008? Or, could you argue that its origins go back as far as 1968 (almost 50 years ago)? Is it a “fad” as many surgeons who do not perform canaloplasty suggest it is? Or, are penetrating surgeries such as trabeculectomy the real fad that will someday be replaced by safer, effective non-penetrating glaucoma surgeries?
You be the judge.
References:
1) Cairns JE. Trabeculectomy. Preliminary report of a new method. Am J Ophthalmol. 1968;66(4):673-679.
2) Grant WM. Further studies on facility of flow through the trabecular meshwork. AMA Arch Ophthalmol. 1958;60(4 Part 1):523-33.
3) Grant WM. Experimental aqueous perfusion in enucleated human eyes. Arch Ophthalmol. 1963;69:783-801. Ibid., p. 676.
4)Stegmann RC. Visco-canalostomy: a new surgical technique for open angle glaucoma. An Inst Barraquer, Spain 1995;5229–2.
