BlueCross and BlueShield of Montana Medical Policy/Codes
Aqueous Shunts for Glaucoma
Chapter: Surgery: Procedures
Current Effective Date: April 18, 2013
Original Effective Date: April 18, 2013
Publish Date: January 18, 2013

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, a variety of devices, including aqueous shunts, are being evaluated as alternative surgical treatments for patients with glaucoma.

Surgical procedures for glaucoma aim to reduce intraocular pressure 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, which can effectively reduce IOP, but commonly results in filtering “blebs” on the eye, and is associated with numerous complications (e.g., leaks or bleb-related endophthalmitis) and long-term failure.  Other surgical procedures (not addressed in this policy) include trabecular laser ablation, deep sclerectomy, which removes the outer wall of Schlemm’s canal and excises deep sclera and peripheral cornea, and viscocanalostomy, which unroofs and dilates Schlemm’s canal without penetrating the trabecular meshwork or anterior chamber.

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 procedure is typically higher than the pressure achieved with standard filtering trabeculectomy. Canaloplasty 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 entire length of Schlemm’s canal and to pass the suture loop through the canal. 

Aqueous shunts may also be placed between the anterior chamber (or vitreous chamber) and Schlemm’s canal to facilitate drainage of aqueous humor.  Established shunts include the Ahmed (New World Medical), Baerveldt (Advanced Medical Optics), Krupin (Eagle Vision) and Molteno (Molteno Ophthalmic).  These devices differ depending on explant surface areas, shape, plate thickness, the presence or absence of a valve, and details of surgical installation.  Generally, the risk of hypotony (low pressure) is reduced with aqueous shunts in comparison with trabeculectomy, but IOP outcomes are higher than after standard guarded filtration surgery. Complications of anterior chamber shunts include corneal endothelial failure and erosion of the overlying conjunctiva.  The risk of postoperative infection is less than after trabeculectomy, and failure rates are similar, with about 10% of devices failing each year.  The primary indication for aqueous shunts is when prior medical or surgical therapy has failed, although some ophthalmologists have advocated their use as a primary surgical intervention, particularly for selected conditions such as congenital glaucoma, trauma, chemical burn, or pemphigoid.

Other aqueous shunts are being developed as minimally penetrating methods to drain aqueous humor from the anterior chamber into an ocular reservoir.  These include the iStent (Glaukos), which is a 1-mm long stent inserted into the end of Schlemm’s canal by either an internal (through the cornea and anterior chamber) or external approach (through the subconjunctiva); the EyePass Bi-Directional Glaucoma Implant (GMP Companies), which is a Y-shaped shunt in which the two arms are placed ab externo into both lumina of Schlemm’s canal; and the Solx DeepLight Gold Micro-Shunt (Solx), which shunts aqueous humor between the anterior chamber and the suprachoroidal space.

Since aqueous humor outflow is pressure-dependent, the pressure in the reservoir and venous system are critical for reaching the target IOP.  Therefore, some devices may be unable 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).  It has been proposed that shunts may be useful to lower IOP in patients with early stage glaucoma to reduce the burden of medications and problems with compliance.  One area of investigation is for patients with glaucoma who require cataract surgery.  An advantage of ab interno shunts is that they may be inserted into the same incision and at the same time as cataract surgery.  In addition, most devices do not preclude subsequent trabeculectomy if needed.  It may also be possible to insert more than one shunt to achieve the desired IOP.  Therefore, health outcomes of interest are the IOP achieved, reduction in medications, ability to convert to trabeculectomy, complications, and durability of the device.




FDA Status



Staar Surgical

Drainage device





Illuminated Catheter





Electrocautery device




New World Medical

Aqueous glaucoma shunt




Advanced Medical Optics

Aqueous glaucoma shunt




Eagle Vision

Aqueous glaucoma shunt




Molteno Ophthalmic

Aqueous glaucoma shunt





Aqueous glaucoma shunt





Aqueous glaucoma shunt

Panel mtg



GMP Companies

Aqueous glaucoma shunt



Solx gold


Aqueous glaucoma shunt



The first generation Ahmed (New World Medical), Baerveldt (Advanced Medical Optics), Krupin (Eagle Vision), and Molteno (Molteno Ophthalmic) aqueous shunts received marketing clearance from the FDA between 1989 and 1993; modified Ahmed and Molteno devices were most recently cleared in 2006.  Their indication for use is “in patients with intractable glaucoma to reduce intraocular pressure where medical and conventional surgical treatments have failed.” The AquaFlow™ Collagen Glaucoma Drainage Device received premarket approval from the FDA in 2001 for the maintenance of sub-scleral space following non-penetrating deep sclerectomy.  The Ex-PRESS™ Mini Glaucoma Shunt received 510(k) marketing clearance in 2003.  The Ex-PRESS shunt is placed under a partial thickness scleral flap and transports aqueous fluid from the anterior chamber of the eye into a conjunctival filtering bleb.

The iStent, EyePass and Solx gold shunt are currently in FDA-regulated trials (the iStent trial’s FDA investigational device exemption [IDE] designates the iStent as a category B device).  In July 2010, the FDA’s Ophthalmic Devices Panel voted that the benefits outweigh the risks of the Glaukos Corporation’s iStent® Trabecular Micro-Bypass Stent, PMA P080030, as indicated for use in conjunction with cataract surgery for the reduction of IOP in subjects with mild to moderate open-angle glaucoma currently treated with ocular hypotensive medication.  The Micro-Shunt and Solx gold shunt have received regulatory approval in Europe.  These are not FDA-approved/cleared for use in the U.S. at this time.


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.


Blue Cross and Blue Shield of Montana (BCBSMT) may consider insertion of aqueous shunts approved by the U.S. Food and Drug Administration (FDA) medically necessary as a method to reduce intraocular pressure in patients with glaucoma where medical therapy has failed to adequately control intraocular pressure.

BCBSMT considers use of an aqueous shunt for all other conditions, including in patients with glaucoma when intraocular pressure is adequately controlled by medications, experimental, investigational and unproven.


FDA-Approved/Cleared Aqueous Shunts

A 2006 Cochrane review evaluated 15 randomized or pseudo-randomized controlled trials (RCTs), with a total of 1,153 participants, on the Ahmed, Baerveldt, Molteno, and Schocket shunts.  Trabeculectomy was found to result in a lower mean intraocular pressure (IOP) (by 3.8 mm Hg) than the Ahmed shunt at one year.  A limitation of this report is that complications were not compared, as the authors considered them to be too variably reported to allow comparative tabulation.  There was no evidence of superiority of one shunt over another.

A literature review on commercially available aqueous shunts, including the Ahmed, Baerveldt, Krupin, and Molteno devices, for an American Academy of Ophthalmology (AAO) technology assessment was published in 2008.  This review indicated that the IOP will generally settle at higher levels (approximately 18 mm Hg) with aqueous shunts than after standard trabeculectomy (14-16 mm Hg) or after trabeculectomy with anti-fibrotic agents 5-fluorouacil or mitomycin C (8-10 mm Hg).   In one study, mean IOPs with the Baerveldt shunt and adjunct medications were found to be equivalent to trabeculectomy with mitomycin C (13 mm Hg).  Five-year success rates for the two procedures were found to be similar (50%).  The assessment concluded that aqueous shunts were comparable with trabeculectomy for IOP control and duration of benefit.  The risk of postoperative infection was less with aqueous shunts than after trabeculectomy.  Complications of aqueous shunts were noted to include: immediate hypotony after surgery; excessive capsule fibrosis and clinical failure; erosion of the tube or plate edge; strabismus; and, very rarely, infection.  The most problematic long-term consequence of anterior chamber tube placement was described as accelerated damage to the corneal endothelium over time.

Implantation of the Ex-PRESS mini shunt under a scleral flap was compared with standard trabeculectomy in a randomized study of 78 patients (80 eyes) with a diagnosis of open-angle glaucoma that could not be controlled with maximal-tolerated medical therapy.  The two groups were similar after randomization, with the exception of difference in the mean age (62 years for the Ex-PRESS group and 69 years for the trabeculectomy group).  At an average 12 months’ follow-up, mean IOP had improved from 23 to 12 mm Hg in the Ex-PRESS group and from 22 to 14 mm Hg in the trabeculectomy group.  Both groups of patients used fewer antiglaucoma medications postoperatively than before the procedure (from 2.8 at baseline to 0.3 in the Ex-PRESS group and from 3.0 at baseline to 0.6 in the trabeculectomy group).  Twelve-month Kaplan-Meier success rates (defined as an IOP of >4 mm Hg or <18 mm Hg without use of antiglaucoma medications) were 82% for the Ex-PRESS shunt and 48% for trabeculectomy.  There was a similar level of postoperative complications in the two groups.

Aqueous Shunts Not Approved by the FDA

At the time this policy was created, the published literature on non-FDA approved/cleared aqueous drainage devices consisted of small case series on the iStent and EyePass.  A search of aqueous shunts and glaucoma online at: during 2008 and 2009 found a number of clinical trials in progress.  The iStent was being studied under an FDA category B investigational device exemption.  Results of this study (described below) were presented to an FDA Ophthalmic Devices Panel in July 2010.  Neither the iStent nor EyePass have received FDA approval/clearance at this time.


A 2008 publication reported interim analysis of a multicenter study of internal implantation of the Glaukos iStent in combination with cataract surgery.  Included were 58 patients with primary open-angle glaucoma (including pseudoexfoliation or pigmentary glaucoma), an IOP of at least 18 mm Hg, taking at least one glaucoma medication, and with a concurrent diagnosis of cataract and glaucoma requiring cataract surgery.  Nine subjects did not meet the study criteria and were excluded from the analysis, in one patient the stent implantation failed, and one subject underwent trabeculectomy and was considered a failure.  There were 12 procedure-related adverse events that were resolved in all but one patient.  Implantation was successful after one or two attempts in 84% of the surgeries.  Interim analysis was reported for the 47 per-protocol subjects who had completed at least six months of follow-up.  For these 47 patients, the IOP decreased from 21.5 mm Hg at baseline to 15.8 mm Hg at six-month follow-up.  Medications decreased from a mean of 1.5 to a mean of 0.5 medications.  At the six-month follow-up 70% of the patients were able to discontinue all previous ocular hypotensive agents.  There were seven device-related adverse events related to obstructions of the stent; two of the patients went on to have a trabeculectomy.  The authors noted that longer follow-up and additional studies were ongoing.

Fea reported a randomized double-blind clinical trial of cataract surgery with or without iStent implantation in 2010.  Inclusion criteria were a previous diagnosis of primary open-angle glaucoma with an IOP above 18 mm Hg at three separate visits, and on one or more hypotensive medications.  Thirty-six patients were randomized in a 1:2 ratio to the iStent or control groups.  The stent was implanted using the same small temporal clear corneal incision (approximately 3.0 mm) that had been used for phacoemulsification and intra-ocular lens placement, and was guided into Schlemm’s canal by an applicator and ab interno gonioscopy.  Follow-up visits with investigators who were masked to the treatment condition were conducted at 24 hours, one week, and 1, 2, 3, 6, 9, 12, and 15 months.  Prescription of hypotensive medications was performed according to pre-set guidelines.  Primary outcomes were IOP and reduction in medication use over 15 months and IOP after a one-month washout of ocular hypotensive agents (16 months postoperatively).  At baseline, IOP was an average of 17.9 mm Hg with 2.0 medications in the stent group and 17.3 mm Hg with 1.9 medications in the control group.  The mean IOP at 15 months was 14.8 mm Hg, with 0.4 medications in the stent group and 15.7 mm Hg with 1.3 medications in the control group.  Eight patients in the stent group (67% of 12) and five in the control group (24% of 21) did not require ocular hypotensive medication.  The author commented that patient compliance is an ongoing concern for most ophthalmologists; therefore, a main goal is to keep the patient as free as possible from medications postoperatively.  After washout of medications, mean IOP was 16.6 in the stent group and 19.2 in the control group.  Two stents were malpositioned, but one of these appeared to be functioning and there were no reported adverse events related to stent implantation.  This small study suggests that without hypotensive medication, the iStent lowers IOP by about 2.5 mm Hg beyond that generated by cataract surgery alone (approximately 25% decrease in the risk of glaucomatous progression).

One year results from the iStent U.S. investigational device exemption (IDE) open-label 29 site multicenter randomized clinical trial were reported to the FDA in 2010 and published in 2011.  The objective of the trial was to measure the incremental effect on IOP from iStent implantation over that of cataract surgery alone and to determine the potential benefit of combining two therapeutic treatments into one surgical event.  A total of 240 patients (mean age of 73 years) with cataracts and mild to moderate open-angle glaucoma (IOP < 24 mm Hg controlled on one to three medications) were randomized to undergo cataract surgery with iStent implantation or cataract surgery only.  The mean number of medications at baseline was 1.5.  The medicated IOP at baseline was 18.7 mm Hg in the stent group and 18.04 in the control group.  After washout, the mean IOP was 25 mm Hg and mean visual acuity (logMAR) was 0.36.  Follow-up visits were performed at 1, 3, 6, and 12 months.  Results were assessed by intent-to-treat analysis with the last observation carried forward and per protocol analysis.  Of the 117 subjects randomized to iStent implantation, 111 underwent cataract surgery with stent implantation, and 106 (91%) completed the 12-month postoperative visit.  Of the 123 subjects randomized to cataract surgery only, 117 underwent cataract surgery and three exited the study because of complications of cataract surgery.  Of the remaining 114 subjects, 112 (91%) completed the 12-month visit.  The proportion of eyes meeting both the primary (unmedicated IOP < 21 mm Hg) and secondary outcomes (IOP reduction > 20% without hypotensive medications) was higher in the treatment group than in the control group at every visit.  At one-year follow-up, 72% of treatment eyes and 50% of control eyes achieved the primary efficacy endpoint.  The proportion of patients achieving the secondary efficacy endpoint was 66% in the treatment group versus 48% in the control group.  Ocular hypotensive medications were initiated later in the postoperative period and used in a lower proportion of patients in the treatment group at every postoperative interval (e.g., 15% vs. 35% at 12 months).  The mean reduction in IOP was similar in the two groups, with a higher level of medication used in the control group (mean of 0.4 medications) in comparison with the treatment group (0.2 medications).  The overall incidence of adverse events was similar between the groups.

The American Academy of  Ophthalmology (AAO) published a 2008 technology assessment on commercially available aqueous shunts, including the Ahmed, Baerveldt, Krupin, and Molteno devices.  The assessment indicated that in general, the IOP will settle at higher levels (approximately 18 mm Hg) with shunts than after standard trabeculectomy (14–16 mm Hg). Five-year success rates of 50% have been found for the two procedures, indicating that aqueous shunts are comparable with trabeculectomy for IOP control and duration of benefit.  (based on level I evidence; well-designed randomized controlled trials).  The assessment indicated that although aqueous shunts have been generally reserved for intractable glaucoma when prior medical or surgical therapy has failed, indications for shunts have broadened (based on level III evidence; case series, case reports, and poor-quality case-control or cohort studies).  The AAO concluded that based on level-I evidence; aqueous shunts offer a valuable alternative to standard filtering surgery or to cyclodestructive therapy for many patients with refractory glaucoma.

2010 Preferred Practice Patterns on primary open-angle glaucoma from the 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 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.

At the time of this 2012 policy this stent had not received FDA approval.  Therefore, it is considered experimental, investigational and unproven.


Randomized controlled trials have shown that the use of shunts results in success rates at least as good as standard filtering surgery, with similar complication rates.  Therefore, use of FDA-approved shunts may be considered medically necessary as a method to reduce intraocular pressure in patients with glaucoma in whom medical treatments have failed to adequately control intraocular pressure.

Other studies have reported use of shunts in patients with both cataracts and less advanced glaucoma, where the IOP is at least partially controlled with medication.  Results from these studies indicate that IOP may be lowered below baseline with decreased need for medication in some patients, but complications may lead to trabeculectomy within six months in a number of eyes.  Since it cannot be determined whether trabeculectomy would have been required had these patients remained on medical therapy, randomized controlled trials with longer follow-up are needed to compare clinical outcomes from patients who have undergone cataract surgery combined with device placement or with continued medical management.  In addition, the Trabectome study group reports that 3% of patients required subsequent glaucoma surgery following combined Trabectome/cataract surgery in a large series.  Therefore, comparative trials with the Trabectome would help to evaluate whether device placement provides a health benefit over an ab interno surgical procedure that does not require permanent device implantation. Aqueous shunts and devices that are not FDA-approved/cleared, as well as all conditions for the approved devices aside from reducing IOP in patients with glaucoma in whom medical therapy has failed, are considered experimental, investigational and unproven.


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. 

ICD-9 Codes
ICD-10 Codes
Procedural Codes: 0191T, 0192T, 0253T
  1. Spiegel, D., Wetzel, W., et al.  Initial clinical experience with the trabecular micro-bypass stent in patients with glaucoma.  Adv Ther (2007) 24(1):161-70.
  2. Dietlein, T.S., Jordan, J.F., et al.  Combined cataract-glaucoma surgery using the intracanalicular Eyepass glaucoma implant: first clinical results of a prospective pilot study.  J Cataract Refract Surg (2008) 34(2):247-52.
  3. Spiegel, D., Garcia-Feijoo, J., et al.  Coexistent primary open-angle glaucoma and cataract: preliminary analysis of treatment by cataract surgery and the iStent trabecular micro-bypass stent. Adv Ther (2008) 25(5):453-64.
  4. Francis, B.A., Minckler, D., et al.  Combined cataract extraction and trabeculotomy by the internal approach for coexisting cataract and open-angle glaucoma: initial results.  J Cataract Refract Surg (2008) 34(7):1096-103.
  5. Minckler, D.,  Mosaed, S., et al.  Trabectome (trabeculectomy-internal approach): additional experience and extended follow-up.  Trans Am Ophthalmol Soc (2008) 106:149-59; discussion 59-60.
  6. Minckler, D.S., Francis, B.A., et al.  Aqueous shunts in glaucoma: a report by the American Academy of Ophthalmology.  Ophthalmology (2008) 115(6):1089-98.
  7. de Jong, L.A.  The Ex-PRESS glaucoma shunt versus trabeculectomy in open-angle glaucoma: a prospective randomized study.  Adv Ther (2009) 26(3):336-45.
  8. Fea, A.M.  Phacoemulsification versus phacoemulsification with micro-bypass stent implantation in primary open-angle glaucoma: randomized double-masked clinical trial.  J Cataract Refract Surg (2010) 36(3):407-12.
  9. U.S. Food and Drug Administration.  FDA Executive Summary, Glaucos, Inc. iStent Trabecular Micro-Bypass Stent (2010) accessed (2011 March).
  10. American Academy of Ophthalmology.  Preferred practice pattern: Primary open-angle glaucoma (2010). accessed (2011 March).
  11. Samuelson, T.W., Katz, L.J., et al.  Randomized Evaluation of the Trabecular Micro-Bypass Stent with Phacoemulsification in Patients with Glaucoma and Cataract.  Ophthalmology (2011 March) 118(3):459-67  
  12. Aqueous Shunts for Glaucoma.  Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Reference (2011 May) 9.03.21
January 2013 

New 2013 BCBSMT medical policy.

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Aqueous Shunts for Glaucoma