Canaloplasty: Overview

Canaloplasty is a highly effective surgical technique for the treatment of open-angle glaucoma. Minimally invasive, it uses breakthrough microcatheter technology to restore the function of the eye’s natural outflow system without the need for a filtering bleb – offering an unprecedented level of efficacy and safety in the surgical treatment of glaucoma. As an added benefit, Canaloplasty can be used in conjunction with existing drug based glaucoma treatments, after laser or other types of incisional surgery and does not preclude or affect the outcome of future surgery.

With over 60,000 procedures performed to date, clinical studies have shown that Canaloplasty provides an improved safety profile with infrequent intra-operative and post-operative complications and does not result in bleb-related issues compared to traditional glaucoma surgery, such as trabeculectomy. During the procedure, the trabecular meshwork plates are stretched by a suture, which is tied and left in situ in Schlemm’s canal, also ensuring that the canal stays open. The canal itself is dilated over 360 degrees to more than 250 microns in diameter, which helps to pop open any previously obstructed collector channel ostia and restore the natural outflow pathways.

Restoring the Outflow Pathways

Canaloplasty works by restoring the natural outflow pathways for aqueous humour, using a technique similar to angioplasty. This advanced procedure delivers a significant degree of IOP reduction by comprehensively opening up all components of the eye’s natural outflow system – 1. the trabecular meshwork, 2. Schlemm’s canal, and 3. the collector channels and distal outflow system.

During the procedure, 360-degree visco-dilation of Schlemm’s canal acts as a form of angioplasty and opens up the ostia of the collector channels, re-establishing outflow. Specifically, the precisely controlled delivery of Healon/Healon GV during withdrawal of the microcatheter separates the compressed tissue planes of the trabecular meshwork, and also triggers the withdrawal of any herniated inner wall tissue from the collector channels.

Sites of Resistance?

One of the challenges of glaucoma treatment is that the location of increased aqueous outflow resistance and how this resistance is generated is unclear. If a glaucoma surgeon were to remove the site(s) where increased outflow resistance resides, IOP would fall. However, if it is not possible to identify the site(s) of increased outflow resistance in a specific POAG eye, it is difficult to determine which parts of the outflow system are more relevant than others in terms of lowering IOP. Consequently, it is important to address all aspects of the ocular outflow system.

The Importance of the Collector Channels

Canaloplasty is the only currently available glaucoma procedure to address blockages in the collector channels.

In a healthy eye, aqueous humor drains from the anterior chamber through progressively smaller channels of the trabecular meshwork into the circumferentially-oriented Schlemm’s canal. From Schlemm’s canal, circuitous channels, known as the collector channels, wind their way toward the surface of the sclera through the intrascleral venous plexus system, joining the episcleral vasculature, which drains into the venous system. It is important to note that the collector channels are not evenly distributed around Schlemm’s canal circumferentially and that outflow is segmental, higher in areas close to the large collector channels.

Studies undertaken in human POAG eyes by Haiyan Gong, MD, PhD (University of Boston) have shown that many of the collector channels may be blocked with herniated trabecular meshwork tissue at 0mmHg and become progressively worse as IOP rises1. This herniated tissue does not recede in POAG eyes although it does in normal eyes. Cannulating the whole of Schlemm’s canal with Canaloplasty, via a process of 360-degree visco-dilation, may “pop” open these herniations and enable full access to collector channel ostia for the egressing aqueous. In the case of other glaucoma treatments, where only a segment of Schlemm’s canal is addressed, or where the trabecular meshwork is targeted in isolation, any herniated tissue would most likely prevent improved outflow.

Bleb-Free Procedure

One of the most significant advantages of Canaloplasty is that it works in the absence of a filtering bleb. This leads to more predictable outcomes and easier post-operative management. Indeed, Canaloplasty provides an improved safety profile and enables surgeons to reduce or eliminate many of the intra-operative and post-operative complications associated with trabeculectomy, including ocular discomfort, bleb scarring over, not scarring enough, and infection.

Research Summary: Haiyan Gong

In POAG eyes fixed at 0 mmHg (N=5), 73 collector channel ostia regions were examined, with 51 showing herniations (70%). In POAG eyes fixed at 10 mmHg (N=2), 22 collector channel ostia regions were examined, with 21 showing herniations (95%). In contrast, in normal eyes fixed at 0 mmHg, 53 collector channel ostia regions were examined, with 8 herniations found (15%). Whilst these herniations were found to be reversible in normal eyes, they were irreversible in the POAG eyes.

1. Source: Cha ED, Xu J, Gong H. Variations in active areas of aqueous humor outflow through the trabecular outflow pathway. Presented at ARVO 2015.

Minimally Invasive. Maximally Effective.

Compared to traditional glaucoma surgery, Canaloplasty offers an improved safety profile with fewer intraoperative and postoperative complications. Canaloplasty can be performed alone, or in conjunction with, phacoemulsification to significantly and durably reduce IOP without the risks and discomfort associated with trabeculectomy. It can therefore be offered earlier in the disease process. Unlike conventional glaucoma surgery, Canaloplasty does not produce a filtering bleb and can therefore be performed on patients who wear contact lenses. In addition, patients who have undergone canaloplasty can continue normal day-to-day activities directly following treatment and require minimal post-operative follow-up.

Video Source: Paolo Brusini, MD. Department of Ophthalmology,
Santa Maria della Misericordia Hospital, Udine, Italy

Clinical Training and Support

Ellex provides comprehensive clinical training and support for each and every Canaloplasty user. The Canaloplasty Adoption Program (CAP) comprises onsite didactic and wet lab training on cadaver eyes, procedure mentoring for live surgery, and post-operative evaluations. Overseen by expert surgical trainers who are seasoned veterans of the operating theater, the CAP is designed to equip the adopting surgeon with the technical skills and knowledge needed for surgical preparation and intervention.

Canaloplasty E-Book

The first in a two-part series, the Canaloplasty E-Book brings together the industry’s leading canaloplasty surgeons to provide clinical and practical insight.

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