GATT (Gonioscopically-Assisted Transluminal Trabeculotomy)

GATT is done by making small incisions into the eye which usually self-seal and do not require stitches. There is no extra implanted device required for this procedure. A suture is fed through a small incision that is made into the drainage canal inside the eye. This suture is pushed all the way around and then pulled to tear open the drainage canal 360°. This essentially bypasses the filtration meshwork and allows for more efficient fluid drainage out of the eye.

GATT is done to reduce the eye pressure by improving the drainage through the existing drainage pathway. It can be done with cataract surgery or as a stand-alone procedure.

GATT can be used to lower eye pressures in patients who are not achieving target pressures, or to lower pressure in patients who rely on multiple eye drops to lower their eye pressures and are not tolerating them well. In this case, a successful GATT can potentially reduce the number of glaucoma drops needed to lower the eye pressures.

The aqueous humour, the fluid that the eye produces to nutrify the cells of the eye, is continually produced and then drained via the internal drainage pathway of the eye. The first part of this pathway has a filtration layer called the trabecular meshwork. This structure provides a partial barrier to the outflow of aqueous fluid. It can be abnormally restrictive in glaucoma patients leading to build up of pressure. GATT essentially involves cutting the trabecular meshwork wide open so that aqueous drainage can occur more easily, and in this way leads to lower eye pressure.

Glaucoma is a group of diseases that causes loss of vision by slow deterioration of the optic nerves. There are many different types of glaucoma with different causes. For this reason, not all procedures are suitable for all types of glaucoma. Your ophthalmologist will discuss what type of glaucoma surgery is best for your type of glaucoma. In general, GATT is suitable for open angle glaucoma (for example, Juvenile Open Angle Glaucoma and Uveitic Glaucoma), where the drainage canal is clearly visible.

Different surgeries also have different rates of success and also different kinds of complications. GATT is a minimally invasive surgery, with a shorter time for the procedure, and faster recovery. Compared with the standard procedures, GATT requires less postoperative visits and has a faster healing time. However, the degree of pressure reduction is not always that much (barring some exceptions), therefore this must be kept in mind in the decision-making process.

You may or may not need to continue the glaucoma medications after surgery. Your ophthalmologist will set a target range for the pressure lowering based on your degree of glaucoma. If you are achieving this target range after surgery without glaucoma drops, you will not need to resume them. If your pressure is still not low enough, you may be asked to resume some or all of the glaucoma drops. This is because in some cases, glaucoma surgeries need to be augmented by glaucoma drops to achieve target pressures.

The surgery is usually done as an outpatient procedure under conscious sedation with a local anesthetic. Most of the operation is comfortable and painless.

There can be a small amount of bleeding during the surgery which usually stops. Occasionally, there can be a lot of bleeding, especially in older patients who have been on blood thinners and have more fragile blood vessels. Bleeding can also be excessive in patients with very high preoperative pressures, which come down abruptly with the surgery. If this happens, there may be a need for reoperation to drain the blood.

As with any intraocular surgery, there is a small risk of infection and inflammation. Antibiotics and anti-inflammatory medications are used during and right after surgery to prevent infection and to improve healing.

For glaucoma surgery, there is a period of time right after surgery when the eye pressure is very unstable and there is high risk for complications like bleeding and excessive pressure lowering (hypotony). Generally, we advise 2-4 weeks of restricted physical activities especially heavy lifting, bending from a standing position, swimming, running and jumping. Depending on your vision, and if you were able to drive before the operation, patients can usually resume driving within 36 hours after surgery or as your ophthalmologist advises.