Complications Specifically Related to Canaloplasty Surgery

Canaloplasty is a surgical approach for patients with open-angle glaucoma. The objective of the procedure is to enhance circumferential outflow of aqueous from Schlemm’s canal to the collector system, improving outflow without creating a filtering bleb. In the procedure, a microcatheter is threaded into the canal using a standard nonpenetrating approach and then passed for 360 degrees. A polypropylene suture is attached to the catheter. The catheter is then retracted 360 degrees during which time viscodilation is performed. The suture remains in the canal, and the ends of the suture are tied together to place constant tension upon the trabecular meshwork (TM). Theoretically, the tension results in opening of the TM, improving outflow and lowering intraocular pressure (IOP). The procedure has increased in popularity and may be a valuable option for patients with open-angle glaucoma who might be at high risk for filtering surgery complications, such as contact lens wearers, patients on blood thinners, and those patients who already failed filtering surgery in the other eye. With the increased popularity of canaloplasty, knowing how to prevent and manage complications of this procedure are crucial skills for today’s glaucoma surgeon. The notion of enhancing circumferential outflow arose from studies of an earlier nonpenetrating procedure, viscocanalostomy (see Chapter 52). In this procedure, a Descemet’s membrane window is created under a scleral flap, and the outflow system is dilated with viscoelastic for 1–2 clock hours. However, in canaloplasty, 360-degree viscodilation is performed, and a tensioning suture is left in Schlemm’s canal to promote canal distension and aqueous outflow. Passing the microcatheter and completing a successful canaloplasty requires specific steps and careful attention to detail. The procedure may be performed under local, regional, or general anesthesia. Fixation of the globe is the first step, using either a corneal or rectus suture. Then, a half-thickness, 4 mm limbus-based scleral flap is created, followed by a deeper scleral flap, which unroofs the canal. The dissection is then taken forward onto Descemet’s membrane to allow for creation of a Descemet’s window, and the deep flap is excised. Schlemm’s canal is next catheterized 360 degrees.