Understanding the Traditional Trabeculectomy Procedure
Ophthalmologists have an impressive array of techniques available to treat patients with glaucoma. For many patients, ideal intraocular pressures can be achieved through pharmacological therapy, or the newly developed minimally invasive glaucoma surgery (MIGS) techniques. Another available option is laser surgery, which is also less invasive than trabeculectomy, the gold standard of surgical treatment.
While laser techniques and MIGS offerings have grown in popularity, they have not yet rendered trabeculectomy obsolete. A number of patients do not get the response they need from minimally invasive techniques, or the response does not prove durable. In these situations, a traditional trabeculectomy may be necessary.
A trabeculectomy entails removing a piece of the trabecular meshwork. This is done to increase aqueous flow in the eye and relieve the pressure, which can build up in the globe. The procedure has been performed since 1900, with the surgery as it is currently performed developed in the 1960s, although numerous improvements have been made since then.
An Overview of the Traditional Trabeculectomy Process
The technique essentially involves creating an opening in the conjunctiva, a thin layer of tissue surrounding the white of the eye adjacent to the iris. This enables the surgeon to access the sclera, a much thicker layer that constitutes the white part of the globe of the eye. A flap is made in the sclera, and a small amount of tissue is removed to create a hole in the front chamber of the eye.
Because the iris would serve as a plug for this hole from the inside of the eye, a piece of the iris is removed just beneath the level of the incision. This keeps the drainage canal from sealing itself. After this, the flap of sclera is replaced and sutured so the hole is partially closed.
The sewn piece of conjunctiva functions as a sort of adjustable valve. It can be made larger or smaller depending on the needs of the patient. Surgeons want to avoid making a hole so large the aqueous runs out too quickly and intraocular pressures drop precipitously.
Then, the conjunctiva is sutured back into place over sclera. This layer can absorb the aqueous that leaks out, similar to a sponge. Aqueous can leak under the conjunctiva and then get safely absorbed back into the body.

Surgeons almost always do a trabeculectomy underneath the upper eyelid. Since fluid collects under the conjunctiva, the surgical site can appear slightly elevated. This tiny bubble is called a bleb. Placing the incision in this location means it is hidden by the eyelid so the site is less noticeable. In addition, the area tends to have fewer blood vessels than surrounding conjunctiva and thus looks whiter than the rest of the eye.
Patients should not be worried about the appearance of a bleb or excessive whiteness. Importantly, this area of the eye has enough space to ensure a second trabeculectomy can be performed if necessary.
Steps to Keep the Trabecular Hole Open
This simple description of the surgery does not do justice to the elegance behind it. The surgery only works if the eye thinks it has healed the opening when, in fact, it has not. The flap construction plays part of the role in achieving this, as does the aqueous flow itself, which makes it difficult for the body to actually form scar tissue.
Surgeons use strong medicine, known as mitomycin-C, at the time of the procedure to discourage healing in the hole that has been created. This drug helps ensure the hole does not close. After the surgery, patients need to use anti-inflammatory eye drops for a couple of weeks. These drops also work to keep the hole open.
After surgery, pressures in the eye are kept slightly above target to help fool the body into thinking it has healed. Then, over time, stiches in the sclera are released to increase flow and move the intraocular pressure closer to the target.
The Risks Involved with a Trabeculectomy
The risks of trabeculectomy are fairly low. Sometimes, the bleb can leak, which results in an intraocular pressure that is too low. This problem manifests with blurred or variable vision. In extreme cases, the walls of the eye can fail and cause shadows which reduce vision, although this does not cause any permanent complications.
Low pressure can sometimes cause permanent changes in vision, so it is important to address it quickly and raise the pressure appropriately. Sometimes, this requires an additional surgery to revise the first. Some patients also experience discomfort related to the bleb. Rarely, bleeding can occur within the eye.
As with any surgery, infection is a risk, although surgeons take the utmost precautions when it comes to keeping the procedure sterile. When infections are caught early, they can easily be treated. Signs of infection include redness, discharge and pain.
