Gonioscopy-Assisted Transluminal Trabeculotomy (GATT)
What Is Gonioscopy-Assisted Transluminal Trabeculotomy (GATT)?
Your eye constantly makes a clear fluid called aqueous humor that flows through the trabecular meshwork into Schlemm canal and then into collector channels. In glaucoma, increased outflow resistance develops at the trabecular meshwork and inner wall of Schlemm canal, causing pressure to build up and damage your optic nerve. GATT works by threading a microcatheter or suture circumferentially within Schlemm canal to create a 360-degree trabeculotomy that bypasses this resistance.
We use a special lens called a goniolens to see the drainage angle inside your eye during the procedure. The catheter incises the trabecular meshwork and inner wall of Schlemm canal throughout the entire 360-degree circumference, creating an opening that allows fluid to drain more easily. This approach targets the source of increased outflow resistance in many types of glaucoma.
GATT is most commonly used to treat primary open-angle glaucoma, which is the most common form of the disease. We may also recommend this procedure for other types of glaucoma where the drainage angle is sufficiently open and accessible.
- Primary open-angle glaucoma in adults
- Juvenile open-angle glaucoma in older children and young adults
- Pigmentary glaucoma caused by pigment affecting drainage
- Pseudoexfoliative glaucoma with flaky material in the drain
- Secondary open-angle glaucoma in selected cases
We typically consider GATT when your eye pressure remains too high despite using multiple glaucoma eye drops. The procedure may also be an option if you cannot tolerate the side effects of glaucoma medications or have trouble remembering to use your drops every day. GATT offers a balance between effectiveness and safety for many patients with mild to moderate glaucoma, and in selected cases of more advanced disease as part of a stepwise treatment approach.
Your ophthalmologist will evaluate whether GATT is right for you based on the type and severity of your glaucoma, your overall eye health, and your treatment goals. Some patients choose GATT to reduce their reliance on daily eye drops and improve their quality of life.
Signs You May Need Glaucoma Surgery
Most people with open-angle glaucoma do not notice any symptoms until the disease has already damaged their vision. You might first notice that your side vision is getting narrower, or you may bump into objects at the edges of your view. Some patients describe seeing blank spots or missing areas in their visual field.
- Gradual loss of peripheral or side vision
- Tunnel vision in advanced stages
- Difficulty seeing in dim lighting
- Trouble with stairs or curbs
While open-angle glaucoma usually progresses slowly, certain warning signs mean you should seek urgent eye care right away. Sudden severe eye pain, headache, blurred vision, seeing halos around lights, nausea, and vomiting are typically signs of acute angle-closure glaucoma, a different type of glaucoma emergency that requires immediate treatment. If you experience these symptoms, go to an emergency room or call our office immediately.
If you notice a sudden change in your vision or new floaters and flashes of light, contact our office immediately. These symptoms might not be related to glaucoma, but they always need prompt evaluation to protect your sight.
Several factors can increase your risk that glaucoma will get worse even with treatment. Age over 60, a family history of glaucoma, and African, Hispanic, or Asian ancestry all raise your risk. High eye pressure readings, thin corneas, and large optic nerve cupping also predict faster progression.
Other health conditions like diabetes, high blood pressure, and heart disease may affect your glaucoma. We carefully monitor patients with multiple risk factors and may recommend surgery like GATT sooner to prevent vision loss.
Testing and Evaluation Before GATT
Gonioscopy is a crucial test that allows us to look directly at the drainage angle inside your eye. We place a special mirrored contact lens on your eye after numbing it with drops. This lens gives us a clear view of the trabecular meshwork and helps us determine if GATT will work for your type of glaucoma.
During gonioscopy, we check whether your drainage angle is open or narrow and look for any abnormal blood vessels, scar tissue, or pigment deposits. The test only takes a few minutes and helps us plan the safest surgical approach for your individual anatomy.
We measure your intraocular pressure, or IOP, at every glaucoma visit using a device called a tonometer. Normal eye pressure ranges from 10 to 21 mmHg, but the target pressure varies for each patient depending on the health of your optic nerve. Your ophthalmologist will also examine your optic nerve through a dilated pupil to look for signs of glaucoma damage.
- Tonometry to measure current eye pressure
- Optic nerve photography to track changes over time
- Visual field testing to map any vision loss
- OCT imaging to measure nerve fiber layer thickness
The ideal candidate for GATT has open-angle glaucoma with a sufficiently open drainage angle visible on gonioscopy and without extensive peripheral anterior synechiae or scarring. We look for patients whose eye pressure is not controlled on medications or who experience side effects from their drops. Your cornea should be clear enough to allow good visualization during surgery.
GATT may not be suitable if you have angle-closure glaucoma that has not been treated, neovascular glaucoma, active uveitis, extensive angle scarring from prior surgery or disease, or severe corneal problems that prevent clear visualization. Some patients with angle-closure glaucoma may be considered after the angle has been opened and if scarring is limited, depending on individual assessment. We will discuss all your surgical options and help you choose the treatment that best fits your specific situation and lifestyle.
The GATT Procedure: What to Expect
Before your GATT procedure, we will review your medical history and current medications. Management of blood thinners and antiplatelet medications is individualized for each patient based on your medical conditions and bleeding risk, and some patients may continue these medications through surgery. Always coordinate with our office and the doctor who prescribed your blood thinner before making any changes. We will give you detailed instructions about when to stop eating and drinking before the procedure.
On the day of surgery, arrive with a clean face free of makeup, lotions, or creams around your eyes. Plan to have someone drive you home afterward, since your vision will be blurry and you will have received sedation or anesthesia.
GATT begins with our ophthalmologist making a tiny incision in the clear part of your eye near the edge. Using the operating microscope and goniolens, we locate the drainage angle inside your eye and create a small opening in the trabecular meshwork to access Schlemm canal. A very thin illuminated microcatheter or fine suture is carefully threaded within Schlemm canal.
We use viscoelastic gel to maintain the front chamber of your eye and improve visualization during the procedure. The catheter travels all the way around Schlemm canal, a full 360 degrees, until it comes back to where it started. We then gently pull the catheter through, completing the trabeculotomy and opening the entire circumference of the drainage pathway. The small incision usually seals itself without stitches, though we may place one or two sutures if needed.
The actual GATT procedure typically takes 30 to 60 minutes to complete. We usually perform GATT under monitored anesthesia care, which means you receive sedation through an IV along with numbing drops and injections around your eye. Some patients have GATT under general anesthesia, especially if the procedure is combined with cataract surgery.
- Local anesthetic drops to numb the eye surface
- Injection of numbing medicine around the eye
- IV sedation to keep you relaxed and comfortable
- General anesthesia if preferred or medically necessary
You should not feel pain during the GATT procedure because of the anesthesia. You may feel some pressure on your eye or be aware of movement, but this should not be painful. Most patients tolerate the surgery well with appropriate anesthesia.
If you do feel any sharp pain during the procedure, let us know immediately so we can give you more numbing medication. Our priority is keeping you safe and comfortable throughout your surgery.
Recovery and Aftercare Following GATT
Your eye will be red, irritated, and possibly swollen for the first few days after GATT. Vision may be blurry or hazy initially, and you might notice some floaters or spots in your vision from blood inside the eye. These symptoms are normal and usually improve within the first week.
You may experience mild to moderate discomfort, scratchiness, or a foreign body sensation in your eye. Over-the-counter pain relievers like acetaminophen are usually enough to manage any discomfort. Applying cool compresses to your closed eyelid can also help reduce swelling and soothe your eye.
Like all surgeries, GATT carries risks that you should understand before the procedure. Some risks are common and expected, while others are rare but serious. Your ophthalmologist will discuss these with you and answer your questions during your preoperative consultation.
- Hyphema or blood in the front of the eye, causing temporary blurred vision and floaters
- Temporary spikes or fluctuations in eye pressure after surgery
- Inflammation and corneal swelling that usually resolve with treatment
- Scarring or peripheral anterior synechiae that may reduce long-term effectiveness
- Need for ongoing glaucoma medications or additional surgery
- Rare but serious risks include infection, significant bleeding, damage to eye structures, or vision loss
We will prescribe anti-inflammatory eye drops, usually a steroid, to use several times daily after GATT. These drops help control inflammation and promote healing inside your eye. You may also need antibiotic drops for the first week to prevent infection. Some patients may develop elevated eye pressure from steroid drops and need close monitoring.
- Steroid drops to reduce inflammation and scarring
- Antibiotic drops to prevent infection
- Artificial tears to keep your eye comfortable
- Some or all of your glaucoma medications, depending on your pressure
Avoid heavy lifting, straining, or bending over at the waist for at least one week after GATT. Do not rub or press on your eye, and try to sleep on the opposite side to avoid putting pressure on the operated eye. You can usually shower and wash your hair, but keep water and soap out of your eye.
Most patients can return to desk work within a few days to a week after surgery. Jobs involving heavy physical labor, dusty environments, or swimming may require a longer recovery period. We will give you specific guidelines based on your occupation and healing progress.
Your first follow-up visit is typically scheduled for the day after surgery so we can check your eye pressure and look for any early complications. Additional appointments are usually scheduled at one week, one month, three months, and six months after GATT. At each visit, we measure your eye pressure and examine the inside of your eye.
Your eye pressure may fluctuate during the first few weeks as your eye heals and adjusts. Some patients experience a temporary pressure spike, while others see an immediate drop. Close monitoring helps us manage your medications and ensure the surgery is working as intended.
Contact our office right away if you experience sudden vision loss, severe eye pain that gets worse, or pain that does not improve with over-the-counter medication. Other urgent symptoms include rapidly increasing redness, thick discharge or pus from the eye, or increased sensitivity to light. If you see sudden flashes of light and new floaters, this may indicate a retinal problem and requires same-day emergency evaluation even outside office hours.
- Sudden decrease or loss of vision
- Severe or rapidly worsening eye pain
- Thick yellow or green discharge from the eye
- Increasing redness and swelling
- Increased sensitivity to light
Treatment Outcomes and Other Options
Studies show that GATT lowers eye pressure in many patients, though results vary based on baseline pressure, glaucoma subtype, prior surgeries, and how success is defined. Some patients experience a 30 to 40 percent reduction from their starting pressure, and pressure may decrease into the mid-to-high teens in many cases, though individual outcomes differ. The procedure often reduces the number of glaucoma medications you need to use.
Success rates vary depending on the type and severity of your glaucoma. Patients with less advanced glaucoma and those who have not had previous eye surgeries tend to have better outcomes. For patients with advanced glaucoma, the target eye pressure may need to be lower than GATT typically achieves, and additional treatment may be necessary. The pressure-lowering effect of GATT varies in duration, and some patients may need additional medications or procedures over time.
Trabeculectomy and tube shunt surgeries generally lower eye pressure more dramatically than GATT, often achieving pressures in the low teens or even single digits. However, these traditional filtering surgeries carry higher risks of serious complications like infection, vision loss, and excessive pressure drops. GATT offers a safer alternative with fewer complications, though it may not lower pressure quite as much.
Recovery from GATT is typically faster and easier than recovery from trabeculectomy or tube shunt surgery. We often recommend GATT for patients with mild to moderate glaucoma who need better pressure control but want to avoid the risks of more invasive surgery. For advanced glaucoma with very high pressures or very low target pressures, traditional filtering surgery may still be the best choice.
GATT is one type of minimally invasive glaucoma surgery, or MIGS, but it tends to lower pressure more effectively than many other MIGS options. Procedures like trabecular micro-bypass stents or goniotomy address only a small section of the drainage channel, while GATT opens the entire 360-degree circumference. This more extensive approach often produces better pressure reduction.
- GATT opens the full drainage canal versus partial treatment
- Greater average pressure reduction than stents alone
- Similar safety profile to other MIGS procedures
- Can be performed alone or with cataract surgery
If your eye pressure remains too high after GATT, we have several options to bring it under better control. You may need to continue or restart some of your glaucoma eye drops to reach your target pressure. Some patients benefit from additional angle-based surgery if the initial treatment was incomplete, or a different type of glaucoma surgery.
If GATT does not achieve adequate control, we may recommend cyclodestructive procedures in selected cases or more aggressive surgical options like trabeculectomy or a tube shunt to better protect your vision. Your ophthalmologist will create an individualized plan based on your eye health and treatment goals.
Frequently Asked Questions
Many patients are able to reduce the number of glaucoma medications they use after GATT, and some stop using drops altogether. However, more than half of patients still need at least one glaucoma medication to keep their pressure at a safe level. Your individual need for medications depends on your target pressure, how well the surgery worked, and how your eye heals.
We generally do not recommend having GATT on both eyes during the same surgery session. Performing the procedure on one eye at a time is safer and allows you to use your other eye for vision while the first eye heals. If both eyes need surgery, we typically space the procedures at least several weeks apart.
Most insurance plans, including Medicare, cover GATT when it is medically necessary to treat glaucoma that is not controlled with medications. Your coverage depends on your specific insurance plan and whether you have met your deductible. We recommend contacting your insurance company before surgery to verify your benefits and understand any out-of-pocket costs.
Yes, GATT can be safely performed at the same time as cataract surgery if you have both cataracts and glaucoma. Combining the procedures means you only need one surgery and one recovery period. Removing your cataract may also provide a small additional benefit in lowering eye pressure.
Both GATT and goniotomy work by incising the trabecular meshwork to improve fluid drainage from your eye. The main difference is that goniotomy treats only a portion of the drainage channel, usually 90 to 180 degrees, while GATT opens the full 360-degree circumference. This more complete treatment with GATT often results in greater and more consistent pressure reduction.
Getting Help for Gonioscopy-Assisted Transluminal Trabeculotomy
If you have been diagnosed with glaucoma and your current treatment is not controlling your eye pressure well enough, talk to our ophthalmologist about whether GATT might be right for you. We will perform a thorough evaluation, discuss your options, and create a personalized treatment plan to protect your vision for years to come.