Goniotomy & Angle Surgery
Goniotomy procedures lower eye pressure by directly opening or removing the diseased trabecular meshwork — the eye's main point of drainage resistance — without leaving any implant behind.
What Is Goniotomy?
Goniotomy is one of the oldest ideas in glaucoma surgery, now modernized into a family of minimally invasive glaucoma surgery (MIGS) techniques. Instead of adding an implant, these procedures address the problem directly: they open or remove the trabecular meshwork itself, the tissue where most of the eye's drainage resistance lives. Closely related techniques include the Kahook Dual Blade, gonioscopy-assisted transluminal trabeculotomy (GATT), the OMNI Surgical System, and the Trabectome.
What Happens Anatomically During the Surgery
Aqueous fluid normally exits the eye by passing through the trabecular meshwork into Schlemm's canal, then into collector channels that return it to the bloodstream. In most open-angle glaucoma, the meshwork and its inner wall are the point of greatest resistance, while the canal and collectors downstream are still relatively healthy.
Using a gonioscopy lens to view the angle directly, the surgeon works through a tiny corneal incision to open that meshwork. A Kahook Dual Blade excises a clean ribbon of meshwork with its two parallel blades; the Trabectome uses fine electrocautery to ablate a strip of it; and GATT passes a microcatheter or suture all the way around Schlemm's canal and pulls it through to unroof the meshwork around the entire 360-degree circumference. The OMNI system can perform this same trabeculotomy and also deliver viscoelastic to dilate the canal (see our Canaloplasty page).
By removing or opening the diseased meshwork, aqueous gains direct access to Schlemm's canal and the collector channels, restoring more natural outflow and lowering eye pressure — without any device left in the eye.
Which Types of Glaucoma It Helps
Angle surgery is versatile. It is used for open-angle glaucoma across a range of severities, and it is especially valuable in congenital and pediatric (juvenile) glaucoma, where trabeculotomy has long been a cornerstone treatment. It can also help in steroid-induced glaucoma, pseudoexfoliation glaucoma, pigment dispersion glaucoma, and other secondary open-angle glaucomas. It works best when the downstream canal and collector channels remain functional; it is not a primary treatment for a physically closed angle or for advanced end-stage disease needing a very low target pressure.
Benefits
Goniotomy-type procedures offer several advantages:
- ✓No implant or foreign device is left in the eye
- ✓The conjunctiva is untouched, keeping trabeculectomy and tube shunt surgery fully available in the future
- ✓Can be performed on its own or combined with cataract surgery through the same incision
- ✓Addresses the true site of the problem — the diseased trabecular meshwork — directly
- ✓Useful across a wide range of glaucoma types, including pediatric and secondary glaucomas
Risks & Considerations
The most common finding after angle surgery is a small amount of bleeding inside the eye (hyphema). This happens because opening the meshwork briefly connects the eye to Schlemm's canal, and a little blood can reflux back through it. This is usually minor and clears on its own over days to a week, though it can temporarily blur vision. Other potential issues include a transient rise in eye pressure early on, the formation of small scar-like adhesions in the angle (peripheral anterior synechiae), and the possibility that pressure reduction is incomplete, so that drops or an additional procedure are still needed. Serious complications are uncommon.
Goniotomy is one branch of MIGS. For how it compares with the iStent, canaloplasty, and the XEN gel stent, see our MIGS Surgery page. When a lower target pressure is required, see our Trabeculectomy and Tube Shunt Surgery pages.
Frequently Asked Questions
What is a goniotomy?
A goniotomy is an angle-based glaucoma surgery that opens or removes a strip of the trabecular meshwork, the tissue responsible for most of the eye's drainage resistance. This lets fluid flow more freely into Schlemm's canal and out of the eye. Modern versions include the Kahook Dual Blade, GATT, and the OMNI system.
What is the Kahook Dual Blade?
The Kahook Dual Blade (KDB) is a single-use instrument with two parallel blades that precisely excise a ribbon of trabecular meshwork, rather than just cutting it, which helps prevent the tissue from healing back over the opening. It is a common, efficient way to perform a goniotomy.
What is GATT?
GATT (gonioscopy-assisted transluminal trabeculotomy) threads a microcatheter or suture 360 degrees around Schlemm's canal and then pulls it through, opening the full circumference of the trabecular meshwork from inside the eye without any external incision.
Is any device left in my eye after a goniotomy?
No. Goniotomy and trabeculotomy remove or open your own tissue and leave nothing behind — there is no stent or implant. This also keeps the conjunctiva untouched, preserving future surgical options.
See a glaucoma specialist. Dr. Robert Gunzenhauser is Harvard-educated and UCLA fellowship-trained in glaucoma, providing expert diagnosis and treatment for Goniotomy (KDB, GATT) at Inland Glaucoma Center in Upland, CA.