Glaucoma Tube Shunt

Glaucoma Tube Shunt Surgery

Author: Aashna Bhakkad

What it is:
A glaucoma tube shunt (also called a glaucoma drainage implant or device) is a surgical procedure used to lower intraocular pressure (IOP) in patients with moderate to advanced glaucoma, especially those who have not responded well to medications or prior surgeries like trabeculectomy.
The procedure involves placing a tiny flexible tube (shunt) in the eye that drains excess aqueous humor to a small plate (reservoir) implanted under the conjunctiva, where the fluid is absorbed into surrounding tissue.

Common Devices Used:

• Ahmed Glaucoma Valve (AGV)

• Baerveldt Glaucoma Implant

• Molteno Implant
  These vary in design (valved vs. non-valved), size, and drainage capacity but function similarly.

How it works:

• The surgeon implants a small plastic plate on the white part of the eye (sclera), usually under the upper eyelid.

• A thin tube is then inserted into the anterior chamber of the eye.

• Aqueous fluid flows through the tube to the plate, where it collects and is gradually absorbed, lowering IOP.

• In valved devices (like Ahmed), the valve helps regulate early postoperative pressure.

Who is a good candidate?
Tube shunts are often used in patients with:

• Failed trabeculectomy or other MIGS procedures

• Neovascular, uveitic, or traumatic glaucoma

• Congenital or pediatric glaucoma

• Extensive conjunctival scarring

• Uncontrolled IOP despite maximal medical therapy
  They are generally reserved for moderate to severe cases or when angle-based surgeries are not viable.

What to Expect Before, During, and After:

• Before: Comprehensive glaucoma evaluation, possible medication adjustment, and lab work if general anesthesia is used

• During:

  • Procedure typically takes 1–1.5 hours

  • Performed under local or general anesthesia

  • The tube and plate are secured to the eye and covered with donor tissue or scleral patch

• After:

  • Eye drops (steroids, antibiotics) for 4–8 weeks

  • Vision may be blurred for a few days to weeks

  • Follow-up visits monitor pressure, tube position, and healing

  • Final healing may take 6–12 weeks

Is Tube Shunt Surgery Safe?
Yes, though more invasive than MIGS, tube shunts are proven to be effective and durable, especially in complex or refractory glaucoma. Compared to trabeculectomy, they offer:

• Lower risk of early postoperative hypotony (especially with valved implants)

• Greater IOP control in high-risk eyes

• Long-term success rates with proper monitoring

Complications:
While generally safe, risks include:

• Hypotony (too low IOP)

• Tube blockage or migration

• Double vision (diplopia)

• Corneal endothelial cell loss or tube-cornea touch

• Blebitis or endophthalmitis (rare but serious infection)

• Chronic discomfort or irritation
  Regular follow-up is essential to monitor tube position and eye pressure.

Benefits of Tube Shunts:

• Effective in eyes with prior failed surgeries

• Long-term pressure control

• Suitable for complex glaucomas (e.g., neovascular, uveitic)

• Can preserve remaining vision in advanced cases

• Valved models offer safer IOP regulation in early recovery

Insurance and Coverage:

• Covered by Medicare and most private insurers when medically necessary

• CPT Code: 66180 (Aqueous shunt to extraocular reservoir)

May require prior authorization depending on insurer and device used

 

Citations:

American Academy of Ophthalmology. Drainage Implant Surgery for Glaucoma. 19 Jan. 2022.
https://www.aao.org/eye-health/treatments/glaucoma-drainage-implant

National Eye Institute. Glaucoma Surgery. U.S. Department of Health and Human Services,
https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/glaucoma/glaucoma-treatment.

Gedde, Steven J., et al. “Treatment Outcomes in the Tube Versus Trabeculectomy (TVT) Study after Five Years of Follow-up.” American Journal of Ophthalmology, vol. 153, no. 5, 2012, pp. 789–803.e2.
https://doi.org/10.1016/j.ajo.2011.10.024.

Ahmed Valve or Baerveldt Implant. Glaucoma Research Foundation.
https://glaucoma.org/ahmed-valve-or-baerveldt-implant/.

Levin, Leonard A., and Daniel M. Albert. Ocular Disease: Mechanisms and Management. Saunders Elsevier, 2010.