BlueCross and BlueShield of Montana Medical Policy/Codes
Viscocanalostomy and Canaloplasty
Chapter: Vision
Current Effective Date: September 24, 2013
Original Effective Date: January 18, 2012
Publish Date: September 24, 2013
Revised Dates: November 12, 2012; July 29, 2013
Description

Glaucoma surgery is intended to reduce intraocular pressure (IOP) when the target IOP cannot be reached with medications.  Due to complications with established surgical approaches such as trabeculectomy, alternative surgical treatments such as transluminal dilation by viscocanalostomy and canaloplasty are being evaluated for patients with glaucoma.

Surgical procedures for glaucoma aim to reduce IOP resulting from impaired aqueous humor drainage in the trabecular meshwork and/or Schlemm’s canal.  In the primary (conventional) outflow pathway from the eye, aqueous humor passes through the trabecular meshwork, enters a space lined with endothelial cells (Schlemm’s canal), drains into collector channels, and then into the aqueous veins.  Increases in resistance in the trabecular meshwork and/or the inner wall of Schlemm’s canal can disrupt the balance of aqueous humor inflow and outflow, resulting in an increase in IOP and glaucoma risk.

Surgical intervention may be indicated in patients with glaucoma when the target IOP cannot be reached pharmacologically.  Trabeculectomy (guarded filtration surgery) is the most established surgical procedure for glaucoma, allowing aqueous humor to directly enter the subconjunctival space.  This procedure creates a subconjunctival reservoir with a filtering “bleb” on the eye, which can effectively reduce IOP, but is associated with numerous and sometimes sight-threatening complications (e.g., leaks, hypotony, choroidal effusions and hemorrhages, hyphemas or bleb-related endophthalmitis) and long-term failure.  Other surgical procedures (not addressed in this policy) include trabecular laser ablation and deep sclerectomy, which removes the outer wall of Schlemm’s canal and excises deep sclera and peripheral cornea.

More recently the Trabectome™, an electrocautery device with irrigation and aspiration, has been used to selectively ablate the trabecular meshwork and inner wall of Schlemm’s canal without external access or creation of a subconjunctival bleb.  IOP with this ab interno (open angle glaucoma) procedure is typically higher than the pressure achieved with standard filtering trabeculectomy.  Aqueous shunts may also be placed to facilitate drainage of aqueous humor.  Complications of anterior chamber shunts include corneal endothelial failure and erosion of the overlying conjunctiva.

Alternative nonpenetrating methods that are being evaluated for glaucoma are viscocanalostomy and canaloplasty.  Viscocanalostomy is a variant of deep sclerectomy, and unroofs and dilates Schlemm’s canal without penetrating the trabecular meshwork or anterior chamber.  A high-viscosity viscoelastic solution, such as sodium hyaluronate, is used to open the canal and create a passage from the canal to a scleral reservoir.  It has been proposed that viscocanalostomy may lower IOP while avoiding bleb-related complications.

Canaloplasty was developed from viscocanalostomy and involves dilation and tension of Schlemm’s canal with a suture loop between the inner wall of the canal and the trabecular meshwork.  This ab externo procedure uses the iTrack™ illuminated microcatheter (iScience Interventional) to access and dilate the length of Schlemm’s canal and to pass the suture loop through the canal.  An important difference between viscocanalostomy and canaloplasty is that canaloplasty attempts to open the entire length of Schlemm’s canal, rather than one section of it.

Since aqueous humor outflow is pressure-dependent, the pressure in the reservoir and venous system is critical for reaching the target IOP.  Therefore, some procedures may not be able to reduce IOP below the pressure of the distal outflow system used, e.g., below 15 mm Hg, and are not indicated for patients for whom very low IOP is desired (e.g., those with advanced glaucoma).  Health outcomes of interest are the IOP achieved, reduction in medications, ability to convert to trabeculectomy if the procedure is unsuccessful, complications, and durability of the procedure.

Regulatory Status

The iTrack (iScience Interventional) received 510(k) marketing clearance from the U.S. Food and Drug Administration (FDA) in 2004 as a surgical ophthalmic microcannula that is indicated for the general purpose of “fluid infusion and aspiration, as well as illumination, during surgery.” In 2008, the iTrack received FDA-clearance for the indication of “catheterization and viscodilation of Schlemm’s canal to reduce intraocular pressure in adult patients with open angle glaucoma.”

Policy

Each benefit plan, summary plan description or contract defines which services are covered, which services are excluded, and which services are subject to dollar caps or other limitations, conditions or exclusions.  Members and their providers have the responsibility for consulting the member's benefit plan, summary plan description or contract to determine if there are any exclusions or other benefit limitations applicable to this service or supply.  If there is a discrepancy between a Medical Policy and a member's benefit plan, summary plan description or contract, the benefit plan, summary plan description or contract will govern.

Medically Necessary

BCBSMT may consider canaloplasty medically necessary as a method to reduce intraocular pressure in patients with chronic primary open-angle glaucoma under the following conditions:

  • Medical therapy has failed to adequately control intraocular pressure, AND
  • The patient is not a candidate for any other intraocular pressure lowering procedure (e.g. trabeculectomy or glaucoma drainage implant) due to a high risk for complications.

Investigational

BCBSMT considers canaloplasty experimental, investigational and unproven under all other conditions, including angle-closure glaucoma.

Viscocanalostomy is considered experimental, investigational and unproven. 

Policy Guidelines

NOTE: Tensioning devices are only able to reduce intraocular pressure (IOP) to the mid-teens, and may be inadequate when very low IOP is needed to reduce glaucoma damage.

Rationale

Viscocanalostomy

A 2010 meta-analysis by Chai and Loon compared the safety and efficacy of viscocanalostomy with the gold standard of trabeculectomy.  Ten randomized controlled trials with a total of 458 eyes (397 patients) with medically uncontrolled glaucoma were included in the analysis.  The number of eyes in each study ranged from 20 to 60, with follow-up ranging from six months to four years.  The majority of eyes (81%) had primary open angle glaucoma, while 16.4% had secondary open angle glaucoma, and 1.7% had primary angle closure glaucoma.  Meta-analysis found that trabeculectomy had a significantly better pressure-lowering outcome.  The difference in intraocular pressure between the treatments was 2.25 mm Hg at six months, 3.64 mm Hg at 12 months, and 3.42 mm Hg at 24 months.  Viscocanalostomy had a significantly higher relative risk (RR) of perforation of Descemet membrane (RR: 7.72).  In contrast, viscocanalostomy had significantly fewer postoperative events compared with trabeculectomy (hypotony RR: 0.29, hyphema RR: 0.50, shallow anterior chamber RR: 0.19, and cataract formation RR: 0.31).  Trabeculectomy had a greater pressure-lowering effect.  Although viscocanalostomy had a better risk profile, most of the adverse events associated with trabeculectomy were considered to be mild and reversible.

One of the studies included in the systematic review was a randomized trial with four-year follow-up by Gilmour et al. from 2009.  Patients (n=43) with open angle glaucoma were randomized to viscocanalostomy (25 eyes) or trabeculectomy (25 eyes) and prospectively followed at regular intervals for up to 60 months.  A successful outcome was defined as intraocular pressure (IOP) less than 18 mm Hg with no medications; a qualified success was defined as IOP less than 18 mm Hg with or without topical treatment.  One patient in each group was lost to follow-up.  At baseline, patients had a mean IOP of 25 mm Hg and were using an average of 1.4 medications.  At mean follow-up of 40 months (range, 6 to 60 months), 10 patients (42%) in the trabeculectomy group had achieved success compared to five patients (21%) in the viscocanalostomy group.  Although 19 patients (79%) in both groups achieved qualified success, fewer trabeculectomy patients required additional topical treatment (50% vs. 83%, respectively) to achieve qualified success.  There were more early postoperative complications in the trabeculectomy group (e.g., hypotony, wound leak, choroidal detachment), but these did not affect the outcome.  At one month, conjunctival blebs were observed in 19 (79%) of the trabeculectomy group and 16 (64%) of the viscocanalostomy group.  At 12 months, blebs were observed in 19 (79%) of the trabeculectomy group and 14 (56%) of the viscocanalostomy group.  The proportion of patients with conjunctival blebs at final follow-up and the statistical significance of these differences were not reported.  It was reported that more bleb manipulations (7 vs. 1) and antimetabolites (5 vs. 1) were needed in the trabeculectomy group.  The three patients who required cataract surgery were all in the viscocanalostomy group.

In 2003, Kobayashi et al. reported a within-subject safety and efficacy comparison of trabeculectomy (with mitomycin C) and viscocanalostomy in 25 patients with bilateral primary open-angle glaucoma who had IOP greater than 22 mm Hg under medical therapy.  Patients were randomly assigned to receive trabeculectomy in one eye and viscocanalostomy (with removal of the internal wall of Schlemm’s canal) in the other eye.  Follow-up was performed at one and three days, one and two weeks, and 1, 2, 3, 4, 5, 6, 9, and 12 months after surgery.  Throughout follow-up, the mean IOP decreased significantly more in trabeculectomy-treated eyes (e.g., from 24.8 to 12.6 mm Hg at 12 months) than in viscocanalostomy-treated eyes (from 25.0 to 17.1 mm Hg).  At 12 months, significantly more trabeculectomy-treated eyes achieved an intraocular pressure less than 20 mm Hg without medication (88% vs. 64%, respectively).  The mean IOP reduction was 48.9% in trabeculectomy-treated eyes and 30.5% in viscocanalostomy-treated eyes.  Overall success, defined as IOP less than 20 mm Hg and IOP reduction greater than 30% with or without glaucoma medication, was not significantly different between the two groups (96% for trabeculectomy and 92% for viscocanalostomy).  Although trabeculectomy had a greater IOP-lowering effect, there were fewer complications with viscocanalostomy (one microperforation of Descemet’s membrane compared with four cases of shallow anterior chamber and five cases of hypotony with IOP < 4 mm Hg).

Canaloplasty

In 2007, Lewis et al. reported interim data analysis from a company-sponsored multicenter (15 centers) safety/efficacy study on canaloplasty using the iTrack microcatheter.  Catheterization of the canal was achieved in 83 of 94 patients enrolled (88%); tension sutures were successfully placed in 74 patients (79%) with a mean IOP of 24 mm Hg.  At three-month follow-up, 57 patients (77% of 74 implanted) had an IOP of 16 mm Hg, and at 12 months, 48 patients (65%) had a mean IOP of 15 mm Hg.  Ten ocular adverse events (11%) were reported, including hyphema (3%), elevated IOP (3%), Descemet’s membrane detachment, hypotony, choroidal effusion, and exposed closure suture (1% each).  Eleven patients (12%) had a subconjunctival bleb, six of which resolved by three months.  The study design included five-year follow-up.   These results were limited by the lack of randomization and high loss to follow-up.

Lewis et al. reported two-year and three-year results from the multicenter study in 2009 and 2011, respectively.  Enrolled in the follow-up study were 157 patients with a diagnosis of primary open-angle glaucoma, pigmentary glaucoma, exfoliative glaucoma, and a baseline IOP of 16 mm Hg or higher before surgery, with a historical IOP of 21 mm Hg or higher.  Exclusion criteria were neovascular disease, uveitis, peripheral anterior synechiae, angle recession, and developmental or secondary glaucoma (except for pigmentary and exfoliative glaucoma).  At baseline, the mean IOP was 23.8 and patients were on an average 1.8 medications; 21% of eyes were on three or more antiglaucoma medications, and 12 eyes (7.6%) were on no medications. Twenty-five eyes (15.9%) were pseudophakic.  Canaloplasty (with or without cataract surgery) was successful in 133 eyes (85%).  Eyes that did not have placement of a tensioning suture were viscodilated to the extent possible by catheterizing the canal from both ostia.  At three years postoperatively, 134 study eyes (85% follow-up) had a mean IOP of 15.2 mm Hg and mean glaucoma medication use of 0.8 medications; four eyes (3%) were on three or more antiglaucoma medications, and 66 eyes (49.3%) were on no medications.  Another seven patients (4.4%) had additional glaucoma surgery.  Six eyes lost two or more lines of corrected visual acuity related to glaucoma progression.  With qualified success defined as achieving IOP of 18 mm Hg or lower (with 0 to 2 medications), success was achieved in 69 of the 89 eyes (77.5%) that had successful suture implantation alone and 24 of the 27 eyes (89%) with successful suture placement combined with phacoemulsification.  Early surgical/postoperative complications included microhyphema (12%), hyphema (10%), elevated intraocular pressure (6%), Descemet membrane detachment (3%), suture extrusion (1%), and hypotony (1%).  Late postoperative complications included cataract (12.7%), transient IOP elevation (6.4%), and partial suture extrusion through the trabecular meshwork (0.6%).

Interim one-year results from a company-sponsored multicenter study were reported in 2008 for 40 patients who had combined canaloplasty and cataract surgery (potential overlap in patients from the study described above).  Inclusion criteria included: a glaucoma diagnosis of primary open-angle glaucoma (POAG), pigmentary glaucoma, exfoliation glaucoma, or POAG with narrow but not occludable angles after laser iridectomy; a treated IOP of 16 mm Hg or higher at baseline; and a historical untreated IOP of 21 mm Hg or higher.  Of the 54 eyes enrolled, successful circumferential catheterization was achieved in 44 eyes (81%), and sutures were successfully placed in 40 eyes (74%).  The 14 eyes (26%) that did not have sutures placed were due to the microcatheter entering a collector channel or meeting other resistance during catheterization; successful suture placement was reported to increase with surgeon experience.  Two eyes were considered failures, with one conversion to trabeculectomy.  Clinical results were reported for 25 patients (46% of 54) who were both due for and reported for 12-month follow-up.  Of these, three eyes (12%) had low subconjunctival blebs at 12 months.  No case of suture erosion through the trabecular meshwork or sclera was noted during follow-up.  IOP was reduced from a mean of 24 mm Hg to 13 mm Hg at six months (reported for 42 eyes; 40 were reported to be successfully treated) and remained under 14 mm Hg in the 25 patients who were evaluated at 12 months.  The number of antiglaucoma medications decreased from a mean of 1.5 medications to a mean of 0.1 at one month and 0.2 at 12 months.  This trial is ongoing, and longer follow-up on a larger number of patients is needed.

Koerber et al. reported on 15 of the patients who participated in the multicenter trial described above who had bilateral POAG and received canaloplasty in one eye and viscocanalostomy in the contralateral eye.  Qualifying preoperative IOPs were 18 mm Hg or greater with historical IOPs of at least 21 mm Hg.  For the canaloplasty eye, the baseline IOP averaged 26.5 mm Hg on 2.1 medications.  All patients had successful suture placement.  Follow-up at 18 months showed IOP of 14.5 on 0.3 medications.  For the viscocanalostomy eye, the baseline eye averaged 24.3 mm Hg on 1.9 medications; follow-up at 18 months showed an average IOP of 16.1 on 0.4 medications.  The reduction in IOP from baseline was significantly greater with canaloplasty (12.0 mm Hg) than with viscocanalostomy (8.2 mm Hg).  There was no loss in visual acuity and no adverse events from either procedure.  The authors noted that this study effectively compares the additional effects of the two major additional maneuvers associated with canaloplasty: first, 360 degrees viscodilation of Schlemm’s canal, as opposed to partial dilation achieved with viscocanalostomy, and second, prolonged opening and tensioning of Schlemm’s canal with suture placement.

Grieshaber et al. reported a prospective series of 60 consecutive black South African patients with POAG who underwent canaloplasty.  The mean preoperative IOP was 45 mm Hg.  At 12 month follow-up, the IOP was 15 mm Hg (n=54), and at 36 months, the IOP was 13.3 mm Hg (n=49).  Eleven patients (18%) were lost to follow-up at three years.  With qualified success defined as achieving IOP of 21 mm Hg or lower (with or without medications), success was achieved in 40 of 49 patients (82%).  When defined as an IOP of 16 mm Hg or less without medications, 47% of eyes met criteria for complete success.  There were no severe complications in this series.

Mosaed and colleagues published a comparative effectiveness review of newer (Trabectome and canaloplasty) and older (trabeculectomy and Baerveldt shunt) surgeries for glaucoma in 2009.  Twelve-month outcomes (intracocular pressure adjunctive medications and complications) were compared after glaucoma-only and combined glaucoma-phacoemulsification surgeries.  The review found that Trabectome and canaloplasty provided modest IOP reduction (to about 16 mm Hg) with minimal intraoperative or postoperative complications.  Results of Baerveldt glaucoma implant IOP reduction were comparable to trabeculectomy (about 12 mm Hg), but typically this shunt required more postoperative IOP-lowering medication (average of 1.3 vs. 0.5 medications, respectively) to achieve a success rate comparable to trabeculectomy.  Patients treated with Trabectome required more medications (average of 1.5) to control IOP than patients treated with canaloplasty (average of 0.6).  The authors concluded that Trabectome and canaloplasty are reasonable surgical therapy choices for patients in which IOPs in the mid-teens seem adequate; although trabeculectomy remains the most effective IOP-lowering procedure, it also has the highest serious complication rates.

Ongoing Clinical Trials

A search of the online site: ClinicalTrials.gov in August 2011 found two randomized trials comparing canaloplasty to trabeculectomy.  Both studies (NCT01228799 and NCT00854256) are expected to enroll 60 subjects with completion in 2012.

2010 Preferred Practice Patterns on primary open-angle glaucoma from the American Academy of Ophthalmology (AAO) states that glaucoma surgical procedures currently under evaluation are canaloplasty with a tensioning suture (Prolene [Ethicon Inc., Somerville, NJ]), ab interno trabeculotomy using the Trabectome (NeoMedix, Tustin, CA), trabecular meshwork bypass stent, and the Ex-PRESS mini glaucoma shunt (Alcon Laboratories, Inc., Ft. Worth, TX).  The AAO considers laser trabeculoplasty as initial therapy in selected patients or as an alternative for patients who cannot or will not use medications reliably due to cost, memory problems, difficulty with instillation, or intolerance to the medication.  The AAO considers nonpenetrating glaucoma surgery to be an alternative to trabeculectomy, although the precise role of nonpenetrating surgery in the surgical management of glaucoma remains to be determined.  Nonpenetrating glaucoma surgery avoids a continuous passageway from the anterior chamber to the subconjunctival space, reducing the incidence of complications such as bleb-related problems and hypotony.  The nonpenetrating procedures have a higher degree of surgical difficulty compared with trabeculectomy and require special instrumentation.  The two main types of nonpenetrating glaucoma surgery are viscocanalostomy and nonpenetrating deep sclerectomy.

The 2008 guidance from the United Kingdom’s National Institute for Health and Clinical Excellence (NICE) stated that the current evidence on the safety and efficacy of canaloplasty for primary open-angle glaucoma is inadequate in both quality and quantity and that this procedure should only be used in the context of research or formal prospective data collection.

NICE and the National Collaborating Centre for Acute Care published guidance on the diagnosis and management of chronic open angle glaucoma and ocular hypertension in 2009.  When comparing penetrating surgery (trabeculectomy) with non-penetrating surgery (deep sclerectomy and viscocanalostomy), the evidence review found moderate quality evidence that trabeculectomy is more effective than non-penetrating surgery in reducing the number of eyes with an unacceptable IOP but was more likely to cause cataract formation and persistent hypotony at 12 to 36 months’ follow-up.  There was very low quality evidence that trabeculectomy is more effective than non-penetrating surgery in reducing IOP from baseline at six and 12 months’ follow-up, but the effect size may be too small to be clinically significant. The guidance recommended offering information on the risks and benefits associated with surgery and offering surgery (type not specified) with pharmacological augmentation to people with chronic open angle glaucoma who are at risk of progressing to sight loss despite treatment.

Summary

Recently, positive two- to three-year outcomes have been reported for canaloplasty, along with a systematic review that found that Trabectome and canaloplasty provided modest IOP reduction (to about 16 mm Hg) with minimal intraoperative or postoperative complications.  When combined with clinical input, evidence is sufficient for canaloplasty to be considered medically necessary in the subset of patients for whom medical therapy has failed to adequately control intraocular pressure and in whom other surgical procedures (e.g. trabeculectomy or a glaucoma drainage implant) are contraindicated.

A number of small randomized trials have been conducted that compare viscocanalostomy with trabeculectomy.  Meta-analysis of these trials indicates that trabeculectomy has a greater pressure-lowering effect than viscocanalostomy.  Although trabeculectomy is associated with greater postoperative risk, most of the adverse events are mild and reversible.  Reduction in IOP has also been shown to be greater with canaloplasty than viscocanalostomy in a small within-subject comparison.  The clinical input for viscocanalostomy was mixed.  Overall, evidence is insufficient to evaluate health outcomes with this procedure in comparison with currently accepted alternatives. Therefore, viscocanalostomy is considered experimental, investigational and unproven.

Coding

Disclaimer for coding information on Medical Policies           

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy.  They may not be all-inclusive.           

The presence or absence of procedure, service, supply, device or diagnosis codes in a Medical Policy document has no relevance for determination of benefit coverage for members or reimbursement for providers.  Only the written coverage position in a medical policy should be used for such determinations.           

Benefit coverage determinations based on written Medical Policy coverage positions must include review of the member’s benefit contract or Summary Plan Description (SPD) for defined coverage vs. non-coverage, benefit exclusions, and benefit limitations such as dollar or duration caps. 

Rationale for Benefit Administration
 
ICD-9 Codes
365.00-365.89
ICD-10 Codes
H40.001 - H40.009, H40.011 - H40.019, H40.021 - H40.029, H40.30X0 - H40.33X4, H40.031 - H40.039, H40.041 - H40.049, H40.40X0 - H40.43X4, H40.051 - H40.059, H40.40X0 - H40.43X4, H40.40X0 - H40.43X4   H40.1510 - H40.1594, H40.0H40, 40X0 - H40.43X4, H40.50X0 - H40.89, H40.61 - H40.069, H40.10X0 - H40.10X4,  H40.11X0 - H40.11X4, H40.141 - H40.149, H40.141 - H40.149, H40.141 - H40.149, H40.141 - H40.149, H40.1210 - H40.1294,  H40.1310 - H40.1394, H40.1510 H40.141 - H40.149  - H40.1594, H40.20X0 - H40.20X4,  H40.211 - H40.219, H40.231 - H40.239, H40.241 - H40.249, H40.2210 - H40.2294, H40.60X0 - H40.63X4, H40.89 - H40.89, H40.811 - H40.819, H40.821 - H40.829, H40.831 - H40.839, H42 - H42, Q15.0 - Q15.0
Procedural Codes: 66174, 66175
References
  1. Kobayashi, H., Kobayashi, K., et al.  A comparison of the intraocular pressure-lowering effect and safety of viscocanalostomy and trabeculectomy with mitomycin C in bilateral open-angle glaucoma.  Graefes Arch Clin Exp Ophthalmol (2003) 241(5):359-66.
  2. Lewis, R.A., von Wolff, K., 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):1217-26. 
  3. Shingleton, B., Tetz, M., et al.  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):433-40. 
  4. National Institute for Health and Clinical Evidence (NICE).  Canaloplasty for primary open-angle glaucoma.  (2008). <http://www.nice.org.uk> accessed (2011 March).
  5. Lewis, R.A., von Wolff, K., 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):814-24.
  6. Mosaed, S., Dustin, L., et al.  Comparative outcomes between newer and older surgeries for glaucoma.  Trans Am Ophthalmol Soc (2009) 107:127-33. 
  7. Gilmour, D.F., Manners, T.D., et al.  Viscocanalostomy versus trabeculectomy for primary open angle glaucoma: 4-year prospective randomized clinical trial.  Eye (Lond) (2009) 23(9):1802-7.
  8. National Institute for Health and Clinical Excellence (NICE).  Glaucoma: Diagnosis and Management of Chronic Open Angle Glaucoma and Ocular Hypertension (2009).  http://www.nice.org.uk (accessed 2011 August).
  9. Chai C, Loon SC. Meta-analysis of viscocanalostomy versus trabeculectomy in uncontrolled glaucoma.  J Glaucoma (2010) 19(8):519-27.
  10. Grieshaber, M.C., Pienaar, A., et al.  Canaloplasty for primary open-angle glaucoma: long-term outcome.  Br J Ophthalmol (2010) 94(11):1478-82.
  11. American Academy of Ophthalmology.  Preferred practice pattern: Primary open-angle glaucoma (2010).  http://one.aao.org (accessed 2011 March).
  12. Lewis, R.A., Von Wolff, K., et al.  Canaloplasty: Three-year results of circumferential viscodilation and tensioning of Schlemm canal using a microcatheter to treat open-angle glaucoma.  J Cataract Refract Surg (2011) (in press).
  13. Viscocanalostomy and Canaloplasty.  Chicago, Illinois:  Blue Cross Blue Shield Association Medical Policy Reference Manual (2011 September) Other 9.03.26.
  14. Koerber, N.J.  Canaloplasty in One Eye Compared With Viscocanalostomy in the Contralateral Eye in Patients With Bilateral Open-angle Glaucoma.  J Glaucoma (2012 February) 21(2):129-34
History
January 2012 Policy on viscocanalostomy and canaloplasty created with literature review through May 2011; clinical input reviewed; canaloplasty may be medically necessary under specified conditions; viscocanalostomy is investigational
November 2012 Policy updated with literature review through June 2012; references 4, 10 and 14 added; policy statement unchanged.
July 2013 Policy formatting and language revised.  Policy statement unchanged.  Removed code 0186T.
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Viscocanalostomy and Canaloplasty