A goniotomy is an eye surgery that lowers eye pressure by cutting into or removing a tiny strip of tissue inside the eye called the trabecular meshwork. This tissue acts as a drain for the fluid that naturally fills the front of your eye, and when it doesn’t work properly, fluid backs up, pressure rises, and the optic nerve can be damaged. That’s glaucoma. Goniotomy opens up that clogged drain from the inside, restoring the natural outflow path.
How the Procedure Works
The front of your eye constantly produces a clear fluid that nourishes the lens and cornea. This fluid normally drains out through a ring of spongy tissue (the trabecular meshwork) and into a tiny channel called the Canal of Schlemm. In glaucoma, the innermost layer of that meshwork creates most of the resistance to drainage. Goniotomy targets this bottleneck directly.
During the surgery, the surgeon looks into the drainage angle of the eye using a special lens called a goniolens, which provides a magnified view of the meshwork. A small blade or specialized instrument is then inserted through a tiny incision in the cornea to cut or strip away a portion of the meshwork. This creates a direct opening from the front chamber of the eye into the drainage canal, allowing fluid to flow out more freely and lowering the pressure.
One important requirement: the cornea needs to be clear enough for the surgeon to see the drainage structures. If the cornea is too cloudy, which sometimes happens when eye pressure has been very high for a long time, a standard goniotomy may not be possible. In rare cases, a tiny camera (endoscope) can be used instead to visualize the angle.
Who Needs a Goniotomy
Goniotomy was originally developed in the 1930s and quickly became the go-to surgery for childhood glaucoma, particularly primary congenital glaucoma, a condition where babies are born with a drainage system that didn’t develop properly. It remains a first-line surgical option for these children today. The best outcomes tend to occur in infants diagnosed between 1 and 24 months of age. One landmark study of 287 eyes found that one or two goniotomies controlled pressure in 94% of patients diagnosed in that age window.
Babies diagnosed at birth (before two months) or children diagnosed after age two still benefit from goniotomy, but their success rates tend to be somewhat lower. Glaucoma caused by other eye abnormalities also responds less predictably. A more recent study of circumferential goniotomy in children with congenital glaucoma reported an overall success rate of about 88%.
Over the past decade, goniotomy has made a major comeback in adult glaucoma treatment as well, thanks to newer instruments and techniques that fall under the umbrella of minimally invasive glaucoma surgery (MIGS). These adult procedures use the same core principle of opening the trabecular meshwork from inside the eye, but with purpose-built devices that allow more precise tissue removal.
Modern Variations of the Procedure
The traditional goniotomy uses a single blade to make an incision across a portion of the meshwork. Today, several variations exist that modify how much tissue is treated and how it’s removed.
- Incisional goniotomy: A small blade cuts through the meshwork, creating a slit that opens into the drainage canal. This is the simplest form and closest to the original technique.
- Excisional goniotomy: Devices like the Kahook Dual Blade use parallel blades to strip away an entire ribbon of meshwork tissue rather than simply cutting it. The idea is that removing tissue completely may reduce the chance of the opening scarring shut.
- 360-degree trabeculotomy (GATT): A suture or microcatheter is threaded all the way around the Canal of Schlemm through a small goniotomy opening, then pulled tight to slice through the entire ring of meshwork at once. This treats the full circumference rather than just a segment.
All of these are performed from inside the eye (called “ab interno”), which means the outer membrane of the eye (the conjunctiva) is left untouched. This is a significant advantage because it preserves the option of more invasive filtering surgeries later if needed.
Goniotomy vs. Trabeculotomy
Trabeculotomy achieves a similar goal but approaches the meshwork from the outside of the eye rather than the inside. A long-term study comparing the two in children with congenital glaucoma found that 360-degree trabeculotomy controlled pressure in 92% of eyes, compared to 58% for standard goniotomy. That difference is significant, and it’s one reason some surgeons prefer trabeculotomy, especially for more severe cases or when the cornea is too cloudy for the surgeon to see the drainage angle clearly.
That said, traditional goniotomy typically treats only about 100 to 180 degrees of the meshwork in a single session, so the comparison isn’t entirely apples-to-apples against a full 360-degree trabeculotomy. Newer circumferential goniotomy techniques like GATT close that gap by treating the entire ring of meshwork from the inside.
What to Expect After Surgery
Goniotomy is a relatively quick procedure, often taking 15 to 30 minutes. For children, it’s performed under general anesthesia. For adults, it’s frequently combined with cataract surgery and done under local anesthesia.
The most common complication is hyphema, a small collection of blood in the front of the eye. In one multicenter study of adult goniotomy patients, this occurred in about 12% of eyes and typically cleared on its own within the first week without requiring any additional procedure. Temporary pressure spikes occurred in about 10% of eyes during the first week, usually managed by adjusting eye drops. Mild corneal swelling was seen in roughly 5% of cases. No vision-threatening complications were reported.
After surgery, you’ll use antibiotic and anti-inflammatory eye drops, generally for several weeks. Soreness and irritation usually settle within a few days. You’ll need to avoid heavy lifting and activities that involve bending forward for the first several weeks. Follow-up visits are frequent in the early postoperative period so your surgeon can monitor pressure and check for complications. A vision assessment is typically done around six to eight weeks after surgery once the eye has stabilized.
For children with congenital glaucoma, the eye pressure is usually checked under anesthesia at follow-up visits. Some children will need a second goniotomy or a different procedure if pressure isn’t adequately controlled after the first surgery.