Gonioscopy-Assisted Transluminal Trabeculotomy (GATT)

Author: Aashna Bhakkad

What is Gonioscopy-Assisted Transluminal Trabeculotomy (GATT)?
GATT is a minimally invasive glaucoma surgery (MIGS) that lowers intraocular pressure (IOP) by opening the eye’s natural drainage system—the Schlemm’s canal—from the inside. Using a gonioscopic view, the surgeon threads a suture or microcatheter through the full 360° of the canal and then removes or tears the inner wall of the trabecular meshwork. This procedure is most effective in open-angle glaucomas and is designed to preserve the eye’s natural anatomy while minimizing risks and recovery time.

How does GATT work?
GATT improves outflow of aqueous humor by creating a circumferential opening in Schlemm’s canal, allowing fluid to bypass the diseased trabecular meshwork. A small goniotomy is made in the nasal angle using a surgical lens, and a flexible suture (e.g., 5-0 Prolene) or illuminated microcatheter is threaded around the canal. Once the full 360° is cannulated, the suture is pulled through, tearing the inner wall and opening the entire canal. This reduces IOP without implants or external drainage.

Who is a good candidate?

• Primary open-angle glaucoma (mild to moderate stages)

• Juvenile or congenital glaucoma

• Pseudoexfoliative or pigmentary glaucoma

• Patients with prior failed MIGS but no major scarring

• Those undergoing combined cataract surgery
  Not recommended for patients with:

• Angle-closure glaucoma

• Heavily scarred angles or extensive synechiae

• Prior filtering surgeries that disrupted Schlemm’s canal

Steps During the Procedure

1. Local anesthesia and mild sedation are administered

2. A goniotomy is performed under gonioscopic view to access Schlemm’s canal

3. A suture or microcatheter is threaded circumferentially (360°) through the canal

4. Once full passage is achieved, the instrument is pulled through to unroof the trabecular meshwork

5. The anterior chamber is flushed, and viscoelastic is removed

6. Antibiotic and anti-inflammatory drops are given postoperatively

What to Expect Before, During, and After

• Before: Standard pre-op eye exam and imaging; discontinue contact lenses; fasting may be required

• During: Procedure takes about 30–45 minutes; performed in an outpatient setting

• After: Mild irritation, redness, and blurred vision are common for a few days
  Eye drops (steroids and antibiotics) will be used for 1–4 weeks
  Follow-up visits monitor IOP and healing. Return to normal activity in 1–2 weeks

Is GATT Safe?
Yes. GATT has a favorable safety profile, especially compared to traditional surgeries like trabeculectomy:

• No external bleb or implant

• Preserves conjunctiva for future surgeries

• Lower risk of hypotony and infection

• Can be repeated or converted to other procedures if needed

Complications
Although rare, some potential risks include:

• Hyphema (blood in the anterior chamber)—common but usually self-resolving

• Transient IOP spikes

• Incomplete trabeculotomy if Schlemm’s canal cannot be fully cannulated

• Scarring or failure requiring additional IOP-lowering treatments

• Inflammation or corneal edema (rare)

Benefits of GATT

• Minimally invasive with no implant or foreign body

• Can be done in combination with cataract surgery

• Effective for various open-angle glaucomas

• Quick recovery and return to normal activities

• Preserves tissue for future surgical options

Insurance and Coverage
Typically covered by Medicare and most private insurers when medically indicated
CPT Code: 65850 (for trabeculotomy); separate code may apply for catheter-based GATT

Citations:

Fellman, Ronald L., and Davinder S. Grover. “MIGS and the Conjunctiva: Preserving the Future.” Glaucoma Today, July–Aug. 2014,
https://glaucomatoday.com/articles/2014-july-aug/migs-and-the-conjunctiva-preserving-the-future.

Grover, Davinder S., et al. “Clinical Outcomes of Gonioscopy-Assisted Transluminal Trabeculotomy in Eyes with Primary Open-Angle Glaucoma.” British Journal of Ophthalmology, vol. 101, no. 6, June 2017, pp. 743–749.
https://bjo.bmj.com/content/101/6/743.

American Academy of Ophthalmology. Primary Open-Angle Glaucoma Preferred Practice Pattern®. 2020.
https://www.aao.org/preferred-practice-pattern/primary-openangle-glaucoma-ppp.