Canaloplasty, a form of nonpenetrating glaucoma surgery, has been proposed as an alternative to trabeculectomy, the traditional surgical treatment of primary open-angle glaucoma (POAG). This document addresses canaloplasty.

Investigational and Not Medically Necessary:

Canaloplasty is considered investigational and not medically necessary for all indications, including but not limited to the treatment of primary open-angle glaucoma (POAG).

At this time, there is a lack of published peer reviewed randomized controlled trials demonstrating the safety and clinical efficacy of canaloplasty. There are various nonrandomized studies which have investigated the procedure. Lewis and colleagues (2007) reported on a nonrandomized, uncontrolled case series of 94 patients who underwent a canaloplasty for POAG with an intraocular pressure (IOP) of at least 16 mm Hg or higher. Seventy-four patients had successful tension suture placement with a resulting mean IOP of 15.3 +/– 3.8 mmHg at one year postop compared to a mean IOP of 24.7 +/- 4.8 mm Hg at baseline. There was a high loss to follow-up; at one year, only 48 of the 74 patients had follow-up. There were many uncontrolled variables such as suture placement versus nonsuture placement, and cataract surgery with canaloplasty versus canaloplasty only, which could influence the results. It is unclear how the uncontrolled variables and patients lost to follow up-affected the reported results. In addition to the uncontrolled variables, this study was limited by lack of randomization.

In an international multicenter prospective study, Shingleton and colleagues (2008) evaluated the safety and efficacy of canaloplasty to treat open-angle glaucoma combined with clear corneal phacoemulsification and posterior chamber intraocular lens (IOL) implantation. Data from 54 eyes that had combined glaucoma and cataract surgery performed by 11 surgeons at 9 study sites were examined. The Schlemm canal and anterior segment angle morphology were assessed by intraoperative and postoperative high resolution ultrasound imaging. Upon comparison of baseline with postoperative data it was found that postoperatively the mean baseline IOP had decreased at 1 month, 3 months, 6 months and 12 months and medication usage had also decreased at 12 months postoperatively. Surgical complications occurred in 5 eyes and included hyphema, Descemet tear, and iris prolapse. Limitations of this study include lack of randomization and lack of a control group present. The authors noted that "additional studies to evaluate this new technique in relation to existing treatments as well as other types of glaucoma are recommended" (Shingleton, 2008).

In an ongoing international multicenter prospective open-label study, Lewis and colleagues (2009) evaluated the two year post surgical safety and efficacy of canaloplasty performed for the treatment of open-angle glaucoma (OAG). The study group consisted of 127 patients (127 eyes) of which 97 eyes (76%) had canaloplasty alone and 30 eyes (24%) with significant cataracts had a combined glaucoma-cataract surgery (phacocanaloplasty). Primary outcome measures included IOP and glaucoma medication use. The authors reported at 24 months, all 127 eyes had a mean IOP of 16.0 mm Hg +/- 4.2 (SD) and mean glaucoma medication use of 0.5 +/- 0.8 (baseline values 23.6 +/- 4.8 mm Hg and 1.9 +/- 0.8 medications). Eyes with canaloplasty alone had a mean IOP of 16.3 +/- 3.7 mm Hg and 0.6 +/- 0.8 medications (baseline values 23.2 +/- 4.0 mm Hg and 2.0 +/- 0.8 medications). Eyes with a combined glaucoma-cataract surgery had a mean IOP of 13.4 +/- 4.0 mm Hg and 0.2 +/- 0.4 medications (baseline values 23.1 +/- 5.5 mm Hg and 1.7 +/- 1.0 medication). Also at 24 months, three eyes (3%) had lost visual acuity. Of these eyes, one had posterior capsule opacification, one had a dense cataract, and the reason for the visual acuity decrease in the remaining eye was not specified. A total of 20 (15.7%) of 127 patients did not meet study analysis criteria due to missed visits. There were 13 post surgical complications reported in 10 eyes and also three complications noted during surgery. Complications reported included suture extrusion, hyphema, and IOP elevation. Limitations of this study included lack of randomization. There was flexibility in patient selection and treatment according to each investigator's current practice. The authors noted "the study design includes additional follow-up and reporting with more extensive subgroup analysis anticipated during the continuing study."

In their Preferred Practice Pattern for primary open-angle glaucoma, the American Academy of Ophthalmology (AAO) (2005) cites limited studies of nonpenetrating glaucoma surgery but does not specifically address canaloplasty. The AAO concludes: "The precise role of nonpenetrating surgery in the surgical management of glaucoma remains to be determined."

The National Institute for Health and Clinical Excellence (NICE) (2008) issued guidance on canaloplasty and stated: "Current evidence on the safety and efficacy of canaloplasty for primary open-angle glaucoma is inadequate in both quality and quantity. Therefore, this procedure should only be used in the context of research or formal prospective data collection."

Although initial study results may show potential promise, there is a need for results from well designed randomized controlled comparative trials to clearly determine the safety and efficacy of this procedure.

According to the National Institutes of Health, glaucoma is the third leading cause of blindness in the United States, and it is estimated 1 to 2% of people over 40 have chronic glaucoma with about 25% of cases undetected. Glaucoma is a group of diseases, which can damage the eye's optic nerve and result in vision loss and blindness. Primary open-angle glaucoma (POAG) is the most common type of glaucoma. POAG is associated with a build up of aqueous fluid pressure within the eye, which can lead to visual field loss and optic nerve damage usually without any associated pain or discomfort. There is no visible abnormality in the anterior chamber angle; however, the aqueous fluid is unable to flow correctly.

In the management of POAG, the goal is to reduce the intraocular pressure (IOP) to retard the development of optic nerve damage. The IOP can be reduced by medical treatment or surgery (alone or in combination). Laser trabeculoplasty is a procedure that leads to tissue remodeling and improved aqueous humor outflow to reduce IOP. The traditional surgery is a trabeculectomy, a filtering surgery in which a surgical excision of a small portion of the trabecular tissue, sclera and, in some cases cornea, is made in order to facilitate drainage of aqueous humor.

Canaloplasty has been proposed as a surgical alternative to trabeculectomy. The canaloplasty procedure utilizes a flexible microcatheter to dilate Schlemm's canal utilizing viscoelastic and a suture is then placed within the canal to enhance aqueous outflow and maintain canal patency. The iScience Surgical Ophthalmic Microcannula, or iTrack^™ (iScience Surgical Corporation, Menlo Park, CA) received 510k clearance on June 22, 2004 as a flexible microcannula designed to allow atraumatic cannulation of spaces in the eye such as the anterior chamber and posterior segment, for infusion and aspiration of fluids during surgery, including saline and viscoelastics.

Hyphema: bleeding in the eye

Schlemm's Canal: a circular canal in the eye that drains aqueous humor from the anterior chamber of the eye into the anterior ciliary veins

Trabecular Tissue: mesh-like structure inside the eye at the iris-scleral junction of the anterior chamber angle; filters aqueous fluid and controls its flow into the canal of Schlemm, prior to its leaving the anterior chamber

The following codes for treatments and procedures applicable to this document are included below for informational purposes.  Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy.  Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Investigational and Not Medically Necessary:
For the procedure codes listed below for all diagnoses; or when the code describes a procedure indicated in the Position Statement section as investigational and not medically necessary.

Peer Reviewed Publications: 

1. Godfrey DG, Fellman RL, Neelakantan A. Canal surgery in adult glaucomas. Curr Opin Ophthalmol. 2009; 20(2):116-121.
2. Lewis RA, von Wolff K, Tetz M, et al. Canaloplasty: circumferential viscodilation and tensioning of Schlemm's canal using a flexible microcatheter for the treatment of open-angle glaucoma in adults: interim clinical study analysis. J Cataract Refract Surg. 2007; 33(7):1217-1226.
3. Lewis RA, von Wolff K, Tetz M, et al. Canaloplasty: circumferential viscodilation and tensioning of Schlemm canal using a flexible microcatheter for the treatment of open-angle glaucoma in adults: two-year interim clinical study results. J Cataract Refract Surg. 2009; 35(5):814-824.
4. Shingleton B, Tetz M, Korber N. Circumferential viscodilation and tensioning of Schlemm canal (canaloplasty) with temporal clear corneal phacoemulsification cataract surgery for open-angle glaucoma and visually significant cataract: one-year results. J Cataract Refract Surg. 2008; 34(3):433-440.
   

Government Agency, Medical Society, and Other Authoritative Publications:

1. American Academy of Ophthalmology (AAO). Primary Open angle glaucoma. Preferred Practice Pattern. Revised September 2005. Available at: http://one.aao.org/CE/PracticeGuidelines/PPP.aspx?sid=ca9ec1b5-2567-4e85-96f6-b6540e5ac5a1. Accessed on December 28, 2009.
2. National Institute for Health and Clinical Excellence (NICE). Canaloplasty for open-angle glaucoma. Interventional Procedure Guidance 260. London, UK: NICE; May 2008. Available at: http://www.nice.org.uk/nicemedia/pdf/IPG260Guidance.pdf. Accessed on December 28, 2009.
3. U.S. Food and Drug Administration 510(k) Premarket Notification Database. Summary of Safety and Effectiveness.  iScience Surgical Ophthalmic Microcannula. No. K041108. Rockville, MD: FDA. June 22, 2004. Available at: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfPMN/pmn.cfm?ID=15050. Accessed on December 28, 2009.

1. National Institutes of Health, the National Eye Institute. Glaucoma- What you should know. Last reviewed April 2006. Available at: http://www.nei.nih.gov/health/glaucoma/glaucoma_facts.asp. Accessed on December 28, 2009.
2. The Glaucoma Foundation. Available at: http://www.glaucomafoundation.org/. Accessed on December 28, 2009.

Canaloplasty
iTrack^™ Microcatheter

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