Medical Policies - Surgery

Viscocanalostomy and Canaloplasty


Effective Date:06-15-2018



Canaloplasty may be considered 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 (IOP); 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.

Canaloplasty is considered experimental, investigational and/or unproven under all other conditions, including angle-closure glaucoma.

Viscocanalostomy is considered not medically necessary.

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


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 (e.g., trabeculectomy), alternative surgical treatments (e.g., transluminal dilation by viscocanalostomy or 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 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 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 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 herein) include trabecular laser ablation and deep sclerectomy, which removes the outer wall of Schlemm 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 canal without external access or creation of a subconjunctival bleb. IOP with this ab interno 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 from anterior chamber shunts include corneal endothelial failure and erosion of the overlying conjunctiva.

Alternative nonpenetrating methods being evaluated to treat glaucoma are viscocanalostomy and canaloplasty. Viscocanalostomy is a variant of deep sclerectomy and unroofs and dilates the Schlemm canal without penetrating the trabecular meshwork or anterior chamber. A high-viscosity viscoelastic solution (e.g., 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, which evolved from viscocanalostomy, involves dilation and tension of the Schlemm 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 the Schlemm 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 the Schlemm canal, rather than 1 section of it.

Because 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 reduce IOP below the pressure of the distal outflow system used (e.g., <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

In 2004, iTrack™ (iScience Interventional) was cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process 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, iTrack™ was cleared by the FDA for “catheterization and viscodilation of [the] Schlemm canal to reduce intraocular pressure in adult patients with open angle glaucoma.” FDA product code: MPA.


This medical policy was originally created in 2012 and has been updated regularly with searches of the MEDLINE database. The most recent literature review was performed through January 25, 2017.


Systematic Reviews

A 2010 meta-analysis by Chai and Loon compared the safety and efficacy of viscocanalostomy with the criterion standard of trabeculectomy. (1) Ten randomized controlled trials (RCTs) 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 6 months to 4 years. Most eyes (81%) had primary open-angle glaucoma (POAG), 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 (IOP) between viscocanalostomy and trabeculectomy was 2.25 mm Hg at 6 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 the Descemet membrane (RR=7.72). In contrast, viscocanalostomy had significantly fewer postoperative events than trabeculectomy (hypotony RR=0.29, hyphema RR=0.50, shallow anterior chamber RR=0.19, cataract formation RR=0.31). Although viscocanalostomy had a better risk profile, most adverse events associated with trabeculectomy were considered to be mild and reversible. Similar results were obtained in a 2014 Cochrane review and meta-analysis by Eldaly et al. that included 2 small randomized trials (total 50 eyes). (2)

Randomized Controlled Trials

One study included in the systematic review by Chai and Loon is a 2009 RCT by Gilmour et al., which reported 4-year follow-up. (3) 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 an IOP less than 18 mm Hg with no medications; a qualified success was defined as an 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, 6-60 months), 10 (42%) patients in the trabeculectomy group had achieved success compared with 5 (21%) patients in the viscocanalostomy group. Although 19 (79%) patients 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 they did not affect outcomes. At 1 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 3 patients who required cataract surgery were in the viscocanalostomy group.

Case Series

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 POAG who had IOP greater than 22 mm Hg under medical therapy. (4) Patients were randomized to trabeculectomy in 1 eye and viscocanalostomy (with removal of the internal wall of the Schlemm canal) in the other eye. Follow-up was performed on certain days, weeks, and months up to 12 months after surgery. Throughout follow-up, 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). At 12 months, significantly more trabeculectomy-treated eyes achieved an IOP less than 20 mm Hg without medication (88% vs 64%, respectively). Mean IOP reduction was 48.9% in trabeculectomy-treated eyes and 30.5% in viscocanalostomy-treated eyes. Overall success (IOP <20 mm Hg) and IOP reduction greater than 30% with or without glaucoma medication did not differ significantly between the groups (96% for trabeculectomy vs 92% for viscocanalostomy). Although trabeculectomy had a greater IOP-lowering effect, viscocanalostomy had fewer complications (1 microperforation of the Descemet membrane vs 4 cases of shallow anterior chamber, and 5 cases of hypotony with IOP <4 mm Hg).

Grieshaber et al. (2015) reported long-term results of viscocanalostomy for a series of 726 patients. (5) Mean IOP before surgery was 42.6 mm Hg. Mean IOP was 15.4 mm Hg at 5 years, 15.5 mm Hg at 10 years, and 16.8 mm Hg at 15 years. Qualified success (with or without medications) at 10 years (< of 18 mm Hg) was 40% in the European population and 59% in the African population. Laser goniopuncture was performed postoperatively on 127 (17.7%) eyes. Fifty-three (7.3%) eyes were considered failures and required reoperation. There were no significant complications.

Stangos et al. (2012) reported the effect of the learning curve on surgical outcomes from viscocanalostomy for a retrospective series of 180 consecutive cases performed by 2 surgeons at a single center in Europe. (6) Overall success (no visual field deterioration with an IOP ≤20 mm Hg) and IOP reduction of 30% or more compared with baseline values improved from 64% for the first 45 and to 91% for the last 45 cases of the series. Complete success (no medications required) improved from 38% to 73%. Surgical complications did not differ significantly between the first and last 45 cases (16 vs 10 respectively).

Section Summary: Viscocanalostomy

Two meta-analyses and 1 systematic review have evaluated RCTs comparing viscocanalostomy with trabeculectomy and reported that trabeculectomy was significantly better than viscocanalostomy at lowering IOP in patients with open-angle glaucoma. Similarly, a randomized, within-subject comparative trial reported that trabeculectomy was significantly better than viscocanalostomy at lowering IOP. However, results of other outcome measures did not differ significantly between trabeculectomy and viscocanalostomy. Viscocanalostomy was associated with fewer complications than trabeculectomy. A nonrandomized uncontrolled study suggested that results of viscocanalostomy were sustained over the long term (up to 15 years) with no significant complications. However, about 7% of treated eyes required reoperation.


Systematic Reviews

A comparative effectiveness review of newer (Trabectome and canaloplasty) and older (trabeculectomy and Baerveldt shunt) surgeries for glaucoma was published in 2009. (7) Twelve-month outcomes (IOP adjunctive medications, complications) were compared after glaucoma-only and combined glaucoma- phacoemulsification surgeries. Reviewers found that Trabectome and canaloplasty provided modest IOP reduction (to ≈16 mm Hg) with minor intraoperative or postoperative complications. Reductions for Baerveldt glaucoma implant IOP were comparable to those for trabeculectomy (≈12 mm Hg), but the Baerveldt shunt required more postoperative IOP-lowering medication (average, 1.3 medications vs 0.5 medications, respectively) to produce a success rate comparable to trabeculectomy. Patients treated with Trabectome required more medications (average, 1.5) to control IOP than patients treated with canaloplasty (average, 0.6). Reviewers concluded that Trabectome and canaloplasty were reasonable surgical choices for patients in whom IOPs in the mid-teens seemed adequate; although trabeculectomy was the most effective IOP-lowering procedure, it also had the most serious complication rates.

Randomized Controlled Trials

In 2015, Matlach et al. reported on an RCT with 62 patients that compared canaloplasty (n=31) with trabeculectomy (n=31) for the treatment of open-angle glaucoma. (8) Patients included had medically uncontrolled or not sufficiently lowered IOP and progression of visual field defects or structural changes to the optic disc over time. The primary end point was an IOP of 18 mm Hg or less or an IOP reduction of at least 20% and less than 21 mm Hg without medication. Complete success at 2 years was achieved in 74.2% of patients after trabeculectomy and 39.1% of patients after canaloplasty (p=0.01). The qualified success rate (with medication) did not differ significantly between the 2 groups, although more patients in the canaloplasty group needed IOP-lowering medication (52.2% vs 25.8%, respectively). Mean absolute IOP reduction was similar for both interventions. There was a trend (p=0.08) for visual acuity to be lower in the canaloplasty group during follow-up. Trabeculectomy was associated with more frequent postoperative complications, including hypotony (37.5%), choroidal detachment (12.5%), and corneal erosion (43.8%). Scarring of the filtering bleb was a late complication in 25% of trabeculectomy patients. One study flaw was the unequal rate of dropouts (23.3% [7/30] for canaloplasty vs 3.1% [1/32] for trabeculectomy) over the 2 years of study. Another study (2015) by this group found higher quality of life (QOL) at 24 months following canaloplasty than trabeculectomy in a questionnaire survey of 327 patients. (9) Canaloplasty patients had a higher positive postoperative mood, higher satisfaction with surgical results, and lower rates of visual and nonvisual symptoms and stress caused by surgery or postsurgical treatment. Difficulties with activities of daily living (e.g., reading) and complaints (e.g., eye burning) were significantly lower in the canaloplasty group. Some questions used were not from validated QOL questionnaires.

Case Series

Most of the primary literature on canaloplasty consists of case series that have compared posttreatment and pretreatment IOP. For example, a retrospective comparative study (2011) evaluated outcomes from 33 eyes (33 patients) that underwent canaloplasty and 46 eyes (46 patients) that underwent trabeculectomy during a 2-year period and had a minimum follow-up of 12 months. (10) This study group was drawn from a larger group of 243 patients who underwent surgery during the same 2-year period (87 canaloplasty procedures, 156 trabeculectomy procedures). The specific procedure was determined by the ability to obtain insurance coverage for canaloplasty, and the groups were comparable in demographics, previous surgery, and visual acuity at baseline. At 12 months postsurgery, mean reduction in IOP from preoperative values was 32% for canaloplasty and 43% for trabeculectomy (p=0.072). IOP was slightly lower in the trabeculectomy group (11.6 mm Hg vs 13.8 mm Hg; p=0.03), and fewer patients in that group needed postoperative glaucoma medications. There was no significant difference in surgical reoperation rates between the 2 procedures (15% canaloplasty vs 11% trabeculectomy). This study had a potential for patient selection bias. Only a minority of surgical patients had 12-month follow-up data, and treatment group assignment depended on insurance status.

In 2007, Lewis et al. reported interim data analysis from a manufacturer-sponsored multicenter (15 centers) safety and efficacy study on canaloplasty using the iTrack microcatheter (11) with 2- and 3-year results reported in 2009 and 2011. (12, 13) The 2011 study included 157 patients with a diagnosis of POAG, pigmentary glaucoma, exfoliative glaucoma, and a baseline IOP of 16 mm Hg or higher before surgery, with a history of 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, mean IOP was 23.8 mm Hg, and patients were on an average of 1.8 medications. Canaloplasty was successful in 133 (85%) eyes. Eyes that did not have placement of a tensioning suture were viscodilated to the extent possible by catheterizing the canal from both ostia. Some of the more common early surgical and postoperative complications included microhyphema (12%), hyphema (10%), elevated IOP (6%), and Descemet membrane detachment (3%). More common late postoperative complications included cataracts (12.7%) and transient IOP elevation (6.4%). At 3 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; 66 (49.3%) eyes were on no medications. Another 7 (4.4%) patients had additional glaucoma surgery. With qualified success defined as achieving an IOP of 18 mm Hg or lower (with 0-2 medications), success was achieved in 69 (77.5%) of the 89 eyes that had successful suture implantation alone and in 24 (89%) of the 27 eyes with successful suture placement combined with phacoemulsification.

Additional reports from this group of investigators included interim 1-year results for 40 patients who had combined canaloplasty and cataracts surgery (potential overlap in patients from the study described earlier) (14) and a within-subjects comparison in 15 patients who participated in the trial described earlier who had bilateral POAG and received canaloplasty in 1 eye and viscocanalostomy in the contralateral eye. (15) For the canaloplasty eye, IOP decreased from 26.5 mm Hg on 2.1 medications to 14.5 mm Hg on 0.3 medications. For the viscocanalostomy eye, IOP decreased from 24.3 mm Hg on 1.9 medications to 16.1 mm Hg on 0.4 medications. Reduction in IOP from baseline was significantly greater with canaloplasty (12.0 mm Hg) than with viscocanalostomy (8.2 mm Hg; p=0.02). No losses in visual acuity or adverse events were reported for either procedure. The investigators noted that this study evaluated the effects of 2 other maneuvers associated with canaloplasty:

360° viscodilation of Schlemm canal, as opposed to partial dilation achieved with viscocanalostomy, and

Prolonged opening and tensioning of Schlemm canal with suture placement. (15)

The same investigators also reported in 2011 on an industry-sponsored, 3-year prospective, multicenter study of 109 open-angle glaucoma patients (109 eyes) who underwent canaloplasty or combined cataract-canaloplasty surgery. (16) All patients had documented visual field loss and met criteria for diagnosis of glaucoma and failure of prior medical or laser therapy. A tensioning suture was successfully placed in 98 (89.9%) eyes, and 96 (88.1%) eyes completed the 3-year follow-up. Of the 13 patients who did not complete follow-up, 4 (3.7%) had additional glaucoma surgery; they were not included in the analysis. In eyes treated with canaloplasty with a successful tensioning suture, IOP decreased from 23 mm Hg on 1.9 medications to 15.1 mm Hg on 0.9 medications. In eyes treated with combined cataract- canaloplasty surgery with a successful tensioning suture, IOP decreased from 24.3 mm Hg on 1.5 medications to 13.8 mm Hg on 0.5 medications. For the 11 eyes that had canaloplasty without suture placement, IOP decreased from 24.4 mm Hg on 1.9 medications to 15.6 mm Hg on 1.2 medications. Late postoperative complications included cataracts (19.1%) and transient IOP elevation (1.8%).

A prospective series with 60 consecutive black South African patients with POAG who underwent canaloplasty was reported by Grieshaber et al. in 2010. (17) Mean preoperative IOP was 45 mm Hg. At 12- month follow-up, IOP was 15 mm Hg (n=54); at 36 months, IOP was 13 mm Hg (n=49). Eleven (18%) patients were lost to follow-up at 3 years. With qualified success defined as achieving an IOP of 21 mm Hg or lower (with or without medications), success was achieved in 40 (82%; 95% CI not reported) of 49 patients. When defined as an IOP of 16 mm Hg or less without medications, 47% (95% CI 36% to 62%) of eyes met criteria for complete success at 36 months. There were no severe complications in this series.

Three-year follow-up from an independent series of 214 patients treated with canaloplasty in Europe was reported by Brusini in 2014. (18) Mean IOP was reduced from 29.4 mm Hg at baseline to 17.0 mm Hg, after excluding 17 (7.9%) patients who later underwent trabeculectomy. At 3 years, IOP was 21 mm Hg or lower in 86.2% of patients, 18 mm Hg or lower in 58.6%, and 16 mm Hg or lower in 37.9%. There was a decrease in mean medication use, from 3.3 at baseline to 1.3 at follow-up. Complications, which included hyphema, Descemet membrane detachment, IOP spikes, and hypotony, were fewer than typically seen with trabeculectomy. Several disadvantages of the procedure were noted, including the inability to complete the procedure in 16.4% of eyes.

In 2015, Voykov et al. reported 5-year follow-up on patients (20 eyes) with open-angle glaucoma who underwent canaloplasty at a single center in Germany. (19) Mean IOP decreased from 25.7 mm Hg at baseline (n=33) to 15.5 mm Hg (n=19) at 1 year, 15.1 mm Hg (n=18) at 3 years, and 14.2 mm Hg (n=18) at 5 years. At each time point, reductions in mean IOP were statistically significant versus baseline (p<0.001). Mean number of medications used was 3.4 at baseline, 1.5 at 1 year, 1.6 at 3 years, and 1.7 at 5 years. At each time point, medication use was significantly lower than baseline (p<0.001). Thirteen (65%) of 20 eyes underwent another surgical procedure due to inadequate IOP control. Median length of time before additional surgery was 24 months (95% confidence interval, 1 to 51 months). The complication rate was low, the most common being hyphema (7/20 [35%] eyes). No sight-threatening complications were reported.

Section Summary: Canaloplasty

Findings from 1 small RCT and 1 comparative effectiveness review have indicated that trabeculectomy is generally superior to canaloplasty for lowering IOP; however, the procedure has been associated with more serious complication rates. Another study has reported that canaloplasty resulted in improved QOL outcomes at 2 years relative to trabeculectomy, although not all QOL measures derived from validated questionnaires. Additionally, several, small, industry-sponsored case series comparing pre- and posttreatment results of canaloplasty showed that most patients achieved sufficient IOP lowering with reduced need for continued medication and relatively few complications.

Clinical Input from Physician Specialty Societies and Academic Medical Centers

In response to requests from the Blue Cross Blue Shield Association (BCBSA) regarding viscocanalostomy, input was received from 1 specialty medical society and 3 academic medical centers while this policy was under review in 2011. Although some considered viscocanalostomy to be medically necessary in a select group of patients who would be at risk for suffering a blinding complication with trabeculectomy, the input was mixed. For example, 1 reviewer considered outcomes with viscocanalostomy to be inferior to other currently used nonpenetrating techniques.

In response to requests from Blue Cross Blue Shield Association (BCBSA) regarding canaloplasty, input was received from 1 specialty medical society and 2 academic medical centers while this policy was under review in 2011. One ophthalmology association provided a statement indicating that the case series cited are sufficient to show efficacy of canaloplasty to lower intraocular pressure to treat open-angle glaucoma. Other reviewers considered canaloplasty to be investigational but medically necessary for a select group of patients (e.g., patients at risk for infection or hypotony, who have surface disease precluding the creation of good trabeculectomy bleb, or that would not be able to cover a glaucoma drainage device implant).

Ongoing and Unpublished Clinical Trials

A search of did not identify any ongoing or unpublished trials that would likely influence this review.

Practice Guidelines and Position Statements

American Academy of Ophthalmology (AAO)

A 2011 technology assessment from the AAO included canaloplasty in its review of novel glaucoma procedures. (20) AAO concluded that all the techniques and devices reviewed were still in the initial stage (≤5 years) of clinical experience and lacking widespread use, with only level III evidence (cohort studies) supporting the procedures. In addition to describing potential advantages and disadvantages of the procedure, it was noted that the long-term effects of a foreign body in the Schlemm canal are not known.

National Institute for Health and Care Excellence (NICE)

The 2008 guidance (updated in 2012) from U.K.’s 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 for research or formal prospective data collection. (21)

In 2009, NICE published guidance on the diagnosis and management of chronic open-angle glaucoma and ocular hypertension. (22) When comparing penetrating surgery (trabeculectomy) with nonpenetrating surgery (deep sclerectomy and viscocanalostomy), NICE found moderate-quality evidence that trabeculectomy is more effective than nonpenetrating surgery in reducing the number of eyes with an unacceptable intraocular pressure (IOP), but was more likely to cause cataract formation and persistent hypotony at 12- to 36-month follow-up. There was very low-quality evidence that trabeculectomy is more effective than nonpenetrating surgery in reducing IOP from baseline at 6- and 12-month follow-up, but the effect size may have been 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 pharmacologic augmentation to people with chronic open-angle glaucoma at risk of progressing to sight loss, despite treatment. In November 2015, NICE determined this guideline should be updated; the expected completion date is July 2017.

Summary of Evidence

For individuals who have open-angle glaucoma who have failed medical therapy who receive viscocanalostomy, the evidence includes small randomized controlled trials (RCTs) comparing viscocanalostomy with trabeculectomy. Relevant outcomes are symptoms, morbid events, quality of life, and medication use. Meta-analysis of these trials has indicated that trabeculectomy has a greater IOP- lowering effect than viscocanalostomy. Reduction in IOP was greater with canaloplasty than viscocanalostomy in a small within-subject comparison. Viscocanalostomy has not been shown to be as good as or better than established alternatives. The evidence is sufficient to determine that the technology is unlikely to improve the net health outcome.

For individuals who have open-angle glaucoma who have failed medical therapy who receive canaloplasty, the evidence includes 1 RCT, 1 comparative effectiveness review, and several case series. Relevant outcomes are symptoms, morbid events, quality of life, and medication use. The RCT found not only significantly higher complete success rates with trabeculectomy than with canaloplasty, but also higher complication rates. The qualified success rate (with medication) was similar between groups. A systematic review found that canaloplasty provided modest IOP reduction (to ≈16 mm Hg) with minor intraoperative or postoperative complications. Further evidence from RCTs is required to corroborate results of this single trial. The evidence is insufficient to determine the effects of the technology on health outcomes.


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CPT Codes

66174, 66175



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2. Eldaly MA, Bunce C, Elsheikha OZ, et al. Non-penetrating filtration surgery versus trabeculectomy for open- angle glaucoma. Cochrane Database Syst Rev. 2014; 2:CD007059. PMID 24532137

3. Gilmour DF, Manners TD, Devonport H, et al. Viscocanalostomy versus trabeculectomy for primary open angle glaucoma: 4-year prospective randomized clinical trial. Eye (Lond). Sep 2009; 23(9):1802-1807. PMID 17293790

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9. Klink T, Sauer J, Korber NJ, et al. Quality of life following glaucoma surgery: canaloplasty versus trabeculectomy. Clin Ophthalmol. 2015; 9:7-16. PMID 25565763

10. Ayyala RS, Chaudhry AL, Okogbaa CB, et al. Comparison of surgical outcomes between canaloplasty and trabeculectomy at 12 months' follow-up. Ophthalmology. Dec 2011; 118(12):2427-2433. PMID 21856008

11. 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. Jul 2007; 33(7):1217-1226. PMID 17586378

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13. Lewis RA, von Wolff K, Tetz M, 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. Apr 2011; 37(4):682-690. PMID 21420593

14. 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. Mar 2008; 34(3):433-440. PMID 18299068

15. Koerber NJ. Canaloplasty in one eye compared with viscocanalostomy in the contralateral eye in patients with bilateral open-angle glaucoma. J Glaucoma. Feb 2012; 21(2):129-134. PMID 21278587

16. Bull H, von Wolff K, Korber N, et al. Three-year canaloplasty outcomes for the treatment of open-angle glaucoma: European study results. Graefes Arch Clin Exp Ophthalmol. Oct 2011; 249(10):1537-1545. PMID 21732110

17. Grieshaber MC, Pienaar A, Olivier J, et al. Canaloplasty for primary open-angle glaucoma: long-term outcome. Br J Ophthalmol. Nov 2010; 94(11):1478-1482. PMID 20962352

18. Brusini P. Canaloplasty in open-angle glaucoma surgery: a four-year follow-up. ScientificWorldJournal. 2014; 2014:469609. PMID 24574892

19. Voykov B, Blumenstock G, Leitritz MA, et al. Treatment efficacy and safety of canaloplasty for open-angle glaucoma after 5 years. Clin Experiment Ophthalmol. Nov 2015; 43(8):768-771. PMID 25952140

20. Francis BA, Singh K, Lin SC, et al. Novel glaucoma procedures: a report by the American Academy of Ophthalmology. Ophthalmology. Jul 2011; 118(7):1466-1480. PMID 21724045

21. National Institute for Health and Care Evidence (NICE). IPG 260. Canaloplasty for primary open-angle glaucoma [IPG260]. 2008 (updated 2012); Available at <> (accessed July 25, 2017).

22. National Institute for Health and Care Excellence (NICE). Glaucoma: diagnosis and management of chronic open angle glaucoma and ocular hypertension [CG85]. 2009; Available at <> (accessed July 25, 2017).

23. Viscocanalostomy and Canaloplasty. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Reference Manual (2017 March) Other 9.03.26.

Policy History:

6/15/2018 Reviewed. No changes.
10/1/2017 Document updated with literature review. Coverage changed for viscocanalostomy from experimental, investigational and/or unproven to not medically necessary.
8/1/2016 Document updated with literature review. Coverage unchanged.
10/15/2015 Reviewed. No changes
4/15/2014 Document updated with literature review. Coverage unchanged.
8/15/2012 New medical policy split out from SUR713.030, Surgical Treatments for Glaucoma policy SUR713.030 will be deleted when these new policies 713.032, 713.033, and 713.034 are effective

Archived Document(s):

Title:Effective Date:End Date:
Viscocanalostomy and Canaloplasty10-01-201706-14-2018
Viscocanalostomy and Canaloplasty08-01-201609-30-2017
Viscocanalostomy and Canaloplasty10-15-201507-31-2016
Viscocanalostomy and Canaloplasty04-15-201410-14-2015
Viscocanalostomy and Canaloplasty08-15-201204-14-2014
Surgical Treatments for Glaucoma04-01-201008-14-2012
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