Glaucoma is a group of eye conditions that progressively damage the optic nerve, which transmits visual information from the eye to the brain. This damage can lead to irreversible vision loss and, if left untreated, blindness. A primary factor in this damage is often elevated intraocular pressure (IOP), the fluid pressure inside the eye. Various treatments are available, including medications, laser therapies, and surgical interventions.
Understanding Glaucoma and Its Surgical Context
Glaucoma typically arises when the eye’s natural drainage system, specifically the trabecular meshwork, does not function as it should. This mesh-like tissue is responsible for draining aqueous humor from the anterior chamber of the eye into Schlemm’s canal, and then into the bloodstream. If this drainage is impaired, aqueous humor can accumulate, leading to increased IOP. Sustained high IOP can compress and damage the delicate fibers of the optic nerve, resulting in blind spots that often begin in peripheral vision and can advance to central vision loss.
When eye drops or laser treatments are not sufficient to manage IOP, surgical intervention becomes a consideration. Traditional glaucoma surgeries, such as trabeculectomy or tube shunts, aim to create new pathways for fluid drainage. While effective, these procedures often involve creating a “bleb” on the eye’s surface, which can carry risks and may complicate future surgical options. The development of less invasive techniques represents an evolution in glaucoma management with a reduced risk profile.
Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) Explained
Gonioscopy-Assisted Transluminal Trabeculotomy, or GATT, is a minimally invasive glaucoma surgery (MIGS) designed to restore the eye’s natural drainage pathway. The core principle of GATT involves creating an opening in the trabecular meshwork to enhance the outflow of aqueous humor.
During the GATT procedure, a surgeon makes incisions in the cornea. A special lens, called a gonioscope, is used to visualize the eye’s drainage angle, allowing the surgeon to precisely locate the trabecular meshwork.
Through a small opening in the drainage system, a microcatheter or a blunted suture is inserted. This wire is then threaded circumferentially through Schlemm’s canal for 360 degrees. Once the catheter or suture has made a full circuit and exits the eye, it is pulled, which tears open the trabecular meshwork.
This action effectively unroofs Schlemm’s canal, directly connecting it to the anterior chamber and allowing fluid to drain into the collector channels and episcleral veins. The goal is to bypass the primary site of outflow resistance, lowering intraocular pressure.
Who Can Benefit from GATT?
GATT is considered for individuals with various forms of open-angle glaucoma, including primary open-angle glaucoma (POAG), juvenile open-angle glaucoma, and certain secondary open-angle glaucomas like steroid-induced glaucoma. It can also be an option for some forms of angle-closure glaucoma. A primary advantage of GATT is its minimally invasive nature, differentiating it from more extensive traditional surgeries.
It does not involve creating a filtering bleb on the eye’s surface, which is a common feature of traditional procedures like trabeculectomy. This “blebless” approach helps preserve the conjunctival tissue, which is the clear membrane covering the white part of the eye. Preserving this tissue is advantageous because it can reduce the risk of complications and keep future surgical options open. Compared to traditional surgeries, GATT involves a faster recovery time and a lower risk profile. It is considered safe and effective for both adults and children, and can be performed as a standalone procedure or in conjunction with cataract surgery.
Life After GATT: Recovery and Expectations
Following the GATT procedure, patients can expect a recovery period that is less demanding than with traditional glaucoma surgeries. Most patients are discharged the same day and will need someone to drive them home due to sedating medications.
Post-operative care typically involves using prescribed eye drops, which usually include a steroid to manage inflammation and an antibiotic to prevent infection. The frequency of steroid eye drops depends on the level of inflammation. Patients are usually seen by their doctor the day after surgery, then about a week later, and again a few weeks after that. Temporary side effects can include blurry vision and, commonly, hyphema, which is blood in the front of the eye. This hyphema usually resolves within about 10 days.
The primary goal of GATT is to reduce intraocular pressure, and studies indicate a significant decrease in IOP after the procedure. For instance, some studies show a mean IOP reduction of over 30% at 6 months, with many patients achieving target pressures below 18 mmHg. This pressure reduction can lead to a decreased reliance on glaucoma medications, with some patients able to reduce or even discontinue their eye drops. GATT aims to control pressure and prevent further vision loss; it does not reverse any vision damage that has already occurred, nor does it cure glaucoma, which remains a chronic condition requiring ongoing monitoring. Visual acuity may temporarily decline after surgery but typically returns to baseline levels.