Gonioscopy-Assisted Transluminal Trabeculotomy

Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) is a minimally invasive glaucoma surgery that opens the eye’s natural drain from the inside to lower intraocular pressure (IOP). High pressure can damage the optic nerve over time, so safely lowering IOP helps protect sight.1

GATT uses a tiny microcatheter or suture to create a 360° trabeculotomy through Schlemm’s canal, restoring the conventional outflow pathway without creating a bleb (no pocket on the eye surface).2

The procedure is performed through a small corneal opening using a mirror (gonioprism) to view the drainage angle. Because it is conjunctiva-sparing (outer eye surface is untouched), future surgeries remain possible. Many adults with open-angle glaucoma (OAG) and some children may be considered for GATT after a full exam and discussion with a glaucoma specialist.

Step by step: After numbing and sterile prep, the surgeon makes a tiny clear-corneal incision and uses a gonioprism to see the angle. A microcatheter (with an illuminated tip) or fine suture is threaded into Schlemm’s canal and guided 360°. The device is pulled through to open the trabecular meshwork and canal along the full circumference—this is the trabeculotomy.3

Because GATT restores the eye’s natural drainage route, there is no external bleb and typically fewer wound restrictions than with traditional filtering surgery.

Where it fits: Glaucoma care is personalized and may include:

• Medications
• Office laser (selective laser trabeculoplasty)
• Canal-based MIGS (GATT, goniotomy)
• More invasive surgeries (trabeculectomy, tube shunt)

Your doctor will match treatment to disease stage, optic nerve health, and target pressure, guided by professional practice patterns.4

Often considered for: Adults with open-angle glaucoma (primary or some secondary forms) who need better pressure control or want to reduce drop burden, and who have an open, viewable angle on gonioscopy. Candidacy also depends on target IOP, optic nerve status, and follow-up ability.5

Studies show GATT can lower IOP and medications in many eyes with open-angle glaucoma, including when combined with cataract surgery.6

Not ideal for: Eyes with angle-closure, very narrow angles, active inflammation, or anatomy that blocks catheter passage. Your surgeon will review risks and alternatives.

How it’s billed (U.S.): GATT is an outpatient eye surgery. When medically necessary, it is typically covered by Medicare Part B and many commercial plans. Out-of-pocket costs depend on deductible, coinsurance, and network status. Request a written estimate including:

• Surgeon fee
• Facility fee (clinic, ASC, or hospital outpatient)
• Anesthesia
• Follow-up visits

7 If done in a hospital outpatient department, billing follows Medicare’s outpatient hospital rules; copays can differ.8

Smart prep: Share insurance cards, confirm if prior authorization is needed, and ask about site-of-service costs. Medicare Advantage and supplements may have different rules.

Benefits you may see: By opening the trabecular meshwork 360°, GATT can significantly lower IOP and reduce daily drops. Multi-year studies report durable pressure control with the advantage of being bleb-less and conjunctiva-sparing.9 It preserves future surgical options.

Limitations & risks: Results vary. Temporary blurred vision, light sensitivity, or small layered hyphema (blood in the front) are common early and usually clear. Pressure spikes or inflammation may occur and are monitored.10

What to expect: Most people go home the same day. The eye may feel scratchy or light-sensitive briefly. Surgeons prescribe anti-inflammatory drops and adjust glaucoma meds as pressure responds. Professional benchmarks emphasize early pressure checks and follow-ups.11

Long-term plans follow guidelines for optic nerve monitoring and visual field testing.12

Call urgently: Severe pain, big vision drop, or rapidly increasing redness need prompt care.

What new studies show: Imaging demonstrates GATT changes aqueous outflow patterns, supporting that restoring the conventional pathway improves pressure.13

Expanding uses: GATT shows promise in some juvenile and secondary glaucomas, including MYOC-JOAG, with sustained IOP reduction and avoidance of filtering surgery.14

If you’re thinking about GATT, schedule a visit with a board-certified ophthalmologist (ideally a glaucoma specialist). Search the AAO directory by location and subspecialty.15

Bring glasses, medication list, prior laser/surgery dates, and recent pressure readings so your doctor can personalize your plan.

Seek urgent care: Sudden severe eye pain, halos, headache, nausea, or rapid vision change may signal dangerous pressure rise.16