Aqueous Shunts and Stents for Glaucoma

POLICY NUMBER

A.9.03.21

DESCRIPTION

Glaucoma surgery is intended to reduce intraocular pressure (IOP) when the target IOP cannot be reached using medications. Due to complications with established surgical approaches (eg, trabeculectomy), a variety of shunts and stents are being evaluated as alternative surgical treatments for patients with inadequately controlled glaucoma.Microstents are also being evaluated in patients with mild-to-moderate open-angle glaucoma currently treated with ocular hypotensive medication.

Glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide and is characterized by elevated intraocular pressure (IOP). In 2020, glaucoma affected approximately 52.7 million individuals globally, with a projected increase to 79.8 million in 2040. Glaucoma has been reported to be 7 times more likely to cause blindness and 15 times more likely to cause visual impairment in Black individuals as compared to White individuals. In the U.S. in 2010, Black individuals had the highest prevalence rate of primary open angle glaucoma at 3.4% compared to 1.7% among White individuals.

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 the Schlemm canal can disrupt the balance of aqueous humor inflow and outflow, resulting in an increase in IOP and glaucoma risk.

Treatment

Ocular Medication

First-line treatment typically involves pharmacologic therapy. Topical medications either increase aqueous outflow (prostaglandins, alpha-adrenergic agonists, cholinergic agonists, Rho kinase inhibitors) or decrease aqueous production (alpha-adrenergic agonists, beta blockers, carbonic anhydrase inhibitors). Pharmacologic therapy may involve multiple medications, have potential side effects, and may be inconvenient for older adults or incapacitated patients.

Surgery

Surgical intervention may be indicated in patients with glaucoma when the target IOP cannot be reached pharmacologically. Surgical procedures for glaucoma aim to reduce IOP from impaired aqueous humor drainage in the trabecular meshwork and/or Schlemm canal. Trabeculectomy (guarded filtration surgery) is the most established surgical procedure for glaucoma, which involves dissecting the conjunctiva, creating a scleral flap and scleral ostomy, then suturing down the flap and closing the conjunctiva, 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., hemorrhage, scarring, hypotony, infection, leaks, 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 canal and excises deep sclera and peripheral cornea), and viscocanalostomy (which unroofs and dilates the Schlemm canal without penetrating the trabecular meshwork or anterior chamber) (see Viscocanalostomy and Canaloplasty ). Canaloplasty 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 entire length of the Schlemm canal and to pass the suture loop through the canal (see Viscocanalostomy and Canaloplasty ).

Insertion of shunts from outside the eye (ab externo) is another surgical option to lower IOP. Examples of ab externo devices cleared by the U.S. Food and Drug Administration (FDA) include the Ahmed, Baerveldt, Molteno, and EX-PRESS mini-shunt, which shunt aqueous humor between the anterior chamber and the suprachoroidal space. These devices differ by explant surface areas, shape, plate thickness, presence or absence of a valve, and details of surgical installation. Generally, the risk of hypotony (low pressure) is reduced with aqueous shunts compared with trabeculectomy, but IOP outcomes are worse than after standard guarded filtration surgery. The risk of postoperative infection is lower with shunts than with trabeculectomy, and failure rates are similar (≈10% of devices fail annually). The primary indication for aqueous shunts is for failed medical or surgical therapy, 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.

Minimally Invasive Glaucoma Surgeries

Minimally invasive glaucoma surgeries (MIGS) are alternative, less invasive techniques that are being developed and evaluated. MIGS, which use microscopic-sized equipment and smaller incisions, involves less surgical manipulation of the sclera and the conjunctiva compared with other surgical techniques. There are several categories of MIGS: miniaturized trabeculectomy, trabecular bypass, milder laser photocoagulation, and totally internal or suprachoroidal stents. Shunts and stents can be administered through an external flap of the conjunctiva and sclera (ab externo) or in a small incision in the cornea with the devices inserted through the anterior chamber of the eye (ab interno). Some ab interno microstents may be inserted with injectors.

Examples of ab interno devices either approved or given marketing clearance by the FDA include the iStent, which is a 1-mm long stent inserted into the end of the Schlemm canal through the cornea and anterior chamber, iStent inject, iStent infinite, and XEN gelatin stent.

Because aqueous humor outflow is pressure-dependent, the pressure in the reservoir and venous system is 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 stents such as the iStent, iStent inject, and Hydrus Microstent may be useful in patients with early-stage glaucoma to reduce the burden of medications and problems with compliance. One area of investigation is patients with glaucoma who require cataract surgery. An advantage of ab interno stents is that they may be inserted into the same incision and at the same time as cataract surgery. Also, most devices do not preclude subsequent trabeculectomy if needed. It may also be possible to insert more than one stent to achieve the desired IOP.

The regulatory status of the various ab externo and ab interno aqueous shunts and microstents is summarized in the table below.

The first-generation Ahmed™ (New World Medical), Baerveldt® (Advanced Medical Optics), Krupin (Eagle Vision), and Molteno® (Molteno Ophthalmic) ab externo aqueous shunts were cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process between 1989 and 1993; modified Ahmed and Molteno devices were cleared in 2006. They are indicated for use “in patients with intractable glaucoma to reduce intraocular pressure where medical and conventional surgical treatments have failed.” The AquaFlow™ Collagen Glaucoma Drainage Device (STAAR Surgical) was approved by the FDA through the premarket approval process for the maintenance of the subscleral space following non-penetrating deep sclerectomy. In 2003, the ab externo EX-PRESS® Mini Glaucoma Shunt was cleared for marketing by the FDA through the 510(k) process.

In 2016, the XEN® Glaucoma Treatment System (Allergan), which consists of the XEN45 Gel Stent preloaded into the XEN Injector, was cleared for marketing by the FDA through the 510(k) process as an ab interno aqueous stent for management of refractory glaucoma. The approval was for patients with refractory glaucoma who failed previous surgical treatment or for patients with primary open-angle glaucoma unresponsive to maximum tolerated medical therapy. The FDA determined that this device was substantially equivalent to existing devices, specifically the Ahmed™ Glaucoma Valve and the EX-PRESS® Glaucoma Filtration Device.

In 2018, the first microstent, the iStent® Trabecular Micro-Bypass Stent preloaded into the iStent inject device (Glaukos) was approved by the FDA through the 515(d) process for use in conjunction with cataract surgery for the reduction of IOP in adults with mild-to-moderate open-angle glaucoma currently treated with ocular hypotensive medication. In 2022, iStent infinite® was FDA-approved for primary open-angle glaucoma when medical and surgical treatment have failed. Notably, this device is not required to be performed in conjunction with cataract surgery and contains 3 stents preloaded into an injector system.

In August 2018, Alcon announced an immediate voluntary recall of the CyPass microstent, which had been approved by the FDA in 2016 for use in conjunction with cataract surgery in adults with mild-to-moderate open-angle glaucoma. The recall was based on five-year postsurgery data from the COMPASS-XT long-term safety study. Results showed a statistically significant increase in endothelial cell loss among patients receiving the CyPass microstent compared with patients receiving cataract surgery alone.

In September 2023, a randomized controlled trial (NCT01881425) reported two-year follow-up outcomes comparing the PRESERFLO MicroShunt (Santen) to trabeculectomy in patients with mild to severe primary open-angle glaucoma inadequately controlled by maximum tolerated medical therapy. As of October 2024, FDA approval of the device is still pending.

Regulatory Status of Aqueous Shunts and Stents

FDA: Food and Drug Administration; PMA: premarket approval.

Related policy - 

• Ophthalmologic Techniques That Evaluate the Posterior Eye Segment for Glaucoma

POLICY

Insertion of ab externo aqueous shunts approved by the U.S. Food and Drug Administration (FDA) may be considered medically necessary as a method to reduce intraocular pressure in individuals with glaucoma where medical therapy has failed to adequately control intraocular pressure.

Insertion of ab interno aqueous stents approved by the U.S. Food and Drug Administration as a method to reduce intraocular pressure in individuals with glaucoma where medical therapy has failed to adequately control intraocular pressure is considered medically necessary.

Implantation of 1 or 2 FDA-approved ab interno stents in conjunction with cataract surgery may be considered medically necessary in individuals with mild-to-moderate open-angle glaucoma treated with ocular hypotensive medication.

Use of an ab externo aqueous shunt for all other conditions, including in individuals with glaucoma when intraocular pressure is adequately controlled by medications, is considered investigational.

Use of ab interno stents for all other conditions is considered investigational.

POLICY EXCEPTIONS

Federal Employee Program (FEP) may dictate that all FDA-approved devices, drugs or biologics may not be considered investigational and thus these devices may be assessed only on the basis of their medical necessity. 

POLICY GUIDELINES

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

Shunts and stents are only able to reduce intraocular pressure (IOP) to the mid-teens and may be inadequate when very low intraocular pressure is needed to reduce glaucoma damage.

Medically Necessary is defined as those services, treatments, procedures, equipment, drugs, devices, items or supplies furnished by a covered Provider that are required to identify or treat a Member's illness, injury or Mental Health Disorders, and which Company determines are covered under this Benefit Plan based on the criteria as follows in A through D:

A.  consistent with the symptoms or diagnosis and treatment of the Member's condition, illness, or injury; and

B.  appropriate with regard to standards of good medical practice; and

C.  not solely for the convenience of the Member, his or her Provider; and

D.  the most appropriate supply or level of care which can safely be provided to Member. When applied to the care of an Inpatient, it further means that services for the Member's medical symptoms or conditions require that the services cannot be safely provided to the Member as an Outpatient.

For the definition of medical necessity, “standards of good medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. BCBSMS makes no payment for services, treatments, procedures, equipment, drugs, devices, items or supplies which are not documented to be Medically Necessary. The fact that a Physician or other Provider has prescribed, ordered, recommended, or approved a service or supply does not in itself, make it Medically Necessary.

Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting. 

POLICY HISTORY

7/24/2008: Policy added.

11/20/2008: Approved by Medical Policy Advisory Committee (MPAC).

05/13/2010: Policy title changed from "Emerging Surgical Treatments for Glaucoma" to "Aqueous Shunts and Devices for Glaucoma." Policy description updated regarding treatment approaches and FDA status of devices. Policy statement revised to indicate that insertion of aqueous shunts approved by the U.S. Food and Drug Administration (FDA) may be considered medically necessary as a method to reduce intraocular pressure in patients with glaucoma where medical therapy has failed to adequately control intraocular pressure. Moved HCPCS codes 0191T and 0192T from non-covered to covered. All other conditions and canaloplasty remain investigational. FEP verbiage added to the Policy Exceptions section.

03/07/2011: Added new CPT codes 0253T and 66175 to the Code Reference section.

08/11/2011: Policy statement revised to indicate that canaloplasty may be considered medically necessary under certain conditions. Moved CPT code 66175 from non-covered to covered.

01/09/2013: In the policy title, changed "Devices" to "Stents." Added the following investigational policy statement: Use of a micro-stent is considered investigational.

04/24/2013: Added ICD-9 codes 365.00-365.9 and 12.67 to the Code Reference section.

01/22/2014: Policy statement revised to state that implantation of a single FDA-approved microstent in conjunction with cataract surgery may be considered medically necessary in patients with mild to moderate open-angle glaucoma currently treated with ocular hypotensive medication. Added the following new 2014 CPT code(s) to the Code Reference section: 66183.

10/17/2014: Policy reviewed; description updated regarding devices. Policy statement unchanged. Policy guidelines updated to state that shunts and stents 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. Removed deleted CPT code 0192T from the Code Reference section.

12/31/2014: Code Reference section updated to revise the description of the following CPT codes: 0191T and 0253T. Effective 01/01/2015. Added the following new 2015 CPT codes: 0376T, 66179, and 66184.

08/21/2015: Code Reference section updated for ICD-10.

11/10/2015: Policy description updated regarding devices. Policy statements unchanged. Policy guidelines updated to add medically necessary and investigative definitions.

04/25/2016: Policy description updated. Policy statements unchanged.

05/27/2016: Policy number A.9.03.21 added.

09/09/2016: Code Reference section updated to make correction: ICD-10 diagnosis code H40.1 should be H40.10X0.

12/30/2016: Code Reference section updated to add new 2017 CPT codes 0449T and 0450T.

04/03/2017: Policy description updated regarding devices. Medically necessary policy statement regarding implantation of a single FDA-approved microstent revised to change "currently treated with ocular hypotensive medication" to "treated with ocular hypotensive medication."

06/23/2017: Code Reference section updated to add new CPT code 0474T, effective 07/01/2017.

01/10/2018: Policy description updated. Policy statements unchanged.

05/16/2019: Policy description updated regarding ocular medication, minimally invasive glaucoma surgeries, and devices. Policy statements updated to clarify the differences between ab externo shunts and ab interno stents. First medically necessary statement separated into two statements: one for ab externo devices and one for ab interno devices. Code Reference section updated to add HCPCS code L8612.

11/05/2019: Medically necessary policy statement updated to change "FDA-approved interno stents" to "FDA-approved ab interno stents."

10/23/2020: Policy description updated regarding devices. Policy statements unchanged.

12/10/2021: Code Reference section updated to add new CPT codes 0671T, 66989, and 66991, effective 01/01/2022.

01/12/2022: Policy description updated regarding minimally invasive glaucoma surgeries and devices. Policy statements unchanged. Policy Guidelines updated to change "Nervous/Mental Conditions" to "Mental Health Disorders" and "Medically Necessary" to "medical necessity."

12/06/2022: Policy description updated regarding new data for glaucoma. Policy statements updated to change "patients" to "individuals."

12/20/2022: Code Reference section updated to revise the description for CPT code 66175, effective 01/01/2023.

10/16/2023: Policy description updated regarding devices. Policy statements unchanged. Code Reference section updated to remove deleted CPT codes 0191T and 0376T.

02/03/2025: Policy description updated regarding devices. Policy statements unchanged.

SOURCE(S)

Blue Cross and Blue Shield Association Policy # 9.03.21

CODE REFERENCE

This may not be a comprehensive list of procedure codes applicable to this policy.     

The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.

Covered Codes

CPT copyright American Medical Association. All rights reserved. CPT is a registered trademark of the American Medical Association.