An update on canaloplasty

August 1, 2012

A versatile procedure and surgery of choise for Dr Mueller.

Trabeculectomy in some form has been the standard in glaucoma surgery for the last several decades, due to it's ability to significantly lower intraocular pressure (IOP). However, new surgical options have developed that are causing physicians to question the necessity of the complications related to trabeculectomy surgery.

Canaloplasty is a greatly enhanced visco-canalostomy. It uses a non-penetrating surgical technique, which is thought to lower IOP by augmenting physiologic outflow through Schlemm's canal, as well as through the intrascleral lake and into the episcleral/scleral venous plexi and suprachoroidal spaces. This is achieved by unroofing Schlemm's canal and creating a Trabeculo-Descemetic window, viscodilating 360 degrees of the canal, and then placing a circumferential suture to provide tension to the trabecular meshwork. Schlemm's canal is viscodilated using the iTrack (iScience Interventional) catheter, which functions as angioplasty, similar to a balloon catheter. The enhancement over visco-canalostomy with full circumferential viscodilation offers the patient a better opportunity for reduced IOP by addressing all areas of disease:

Collector Channels - allows distal outflow as viscodilation within Schlemm's canal opens sealed collector channel ostia to permit greater outflow.

Tensioning suture - distends the inner wall of Schlemm's canal and maintains patency of the canal, enhancing aqueous outflow through the trabecular meshwork.

Data have confirmed that canaloplasty leads to a significant and sustained IOP reduction with a safety profile that is more favourable than trabeculectomy.2 A prospective study of 32 patients with medically uncontrolled open angle glaucoma underwent primary canaloplasty with a followup time of more than one year. The mean IOP at baseline was 27.3±5.6 mmHg, and dropped at 12 months to 12.8±1.5 mmHg and at 18 months to 13.1±1.2 mmHg (P < 0.001). The number of medications dropped from 2.7±0.5 before surgery to 0.1±0.3 after surgery (P < 0.001), and best-corrected visual acuity at last visit (0.38±0.45; range: 0 to 1.8) was comparable with that of preoperative values (0.36±SD 0.37; range: 0 to 1.6) (P = 0.42).

Indications

Canaloplasty is indicated for all openangle glaucoma. The majority of patients that I see are on a combination of two to four medications, and in most of them IOP is still unregulated. Noncompliance for a variety of reasons is often an issue. When I have a patient who is on two or more medications or is allergic to medications, noncompliant or shows deterioration of the visual field, I propose canaloplasty. I perform it both in cases that are just starting to show visual field deterioration as well as very advanced cases where there is very little visual field left. Canaloplasty can be very effective in patients with greater than average concerns about vision loss, such as those with high myopia, diabetic retinopathy or macular oedema.

Canaloplasty is also particularly indicated for patients in whom trabeculectomy is expected to fail. This includes patients in whom trabeculectomy failed in the other eye or those who have significant ocular disease. I find canaloplasty to be an excellent primary procedure, and will perform it earlier in patients because the safety profile is good.