Trabeculectomy is a type of eye surgery performed to treat glaucoma. It involves making a channel for fluid to exit the eye and lower the pressure inside the eye. The fluid does not flow directly out into the tears. Instead it is collected under the mucous membrane on the surface of the eye called the conjunctiva. From there the fluid is reabsorbed by the body or very slowly crosses the conjunctiva.
In its simplest sense, glaucoma is an eye disease in which damage to the optic nerve impairs vision. The optic nerve is the fiber-optic cable that transmits visual images from our eyes to our brain.
Glaucoma is most often associated with high pressure in the eye. Normally, inside the eye fluid is produced and drained at a relatively constant rate. In the most common type of glaucoma, the drainage of fluid through the trabecular meshwork is impaired, leading to high pressure.
Diagram showing the location where the optic nerve leaves the eye en route to the brain. When the pressure is too high in the eye, the fluid pushes back on the optic nerve and damages it. This leads to vision loss, especially in the periphery.
What is the trabecular meshwork?
The trabecular meshwork is where fluid in the eye drains from. It is located at the base of the cornea near the ciliary body. The fluid drains through this meshwork into a series of canals, and then into the bloodstream.
If the trabecular meshwork becomes “clogged”, drainage of fluid decreases. This can lead to high pressure inside the eye (which can lead to glaucoma).
Diagram showing the normal production and drainage of fluid in the eye. Fluid is made in the ciliary body and drained through the trabecular meshwork.
Why would a trabeculectomy be performed?
There are many treatment options for glaucoma. They include drops to lower the pressure, laser treatment to improve flow throughthe trabecular meshwork and various types of surgery.
Usually, a trabeculectomy is only performed if other options such as drops and lasers have failed. This is because as with any surgery, there are complications that can occur.
A trabeculectomy is performed to control the pressure inside the eye. It does not reverse damage already done from glaucoma. However, it may help to prevent further damage.
What type of anesthesia is used for surgery?
A trabeculectomy is usually performed under local anesthesia. This means that only the eye and tissues surrounding the eye are “frozen”. The patient is awake during surgery, however some patients will be given a sedative to make the surgery more comfortable.
What happens during surgery?
In trabeculectomy, the ophthalmologist removes a small piece of tissue from the peripheral cornea and trabecular meshwork. This creates an opening through which fluid can drain directly out of the eye into a pocket or “bleb” underneath the conjunctiva.
Fluid that drains underneath the conjunctiva is simply absorbed by the surrounding blood vessels. Fluid is not drained to the external surface of the eye because this would provide an entry for bacteria into the eye.
Diagram showing the outcome of surgery. Fluid is able to drain into a pocket underneath the conjunctiva. THIS IMAGE WILL BE REPLACED WITH A PROFESSIONAL ILLUSTRATION SOON.
What are the long-term results of trabeculectomy?
Trabeculectomy has shown in studies to be very effective in controlling pressure in the eye long-term. The complication rate from surgery is low, and most patients will no longer need to take eye drops after surgery (except for in the first few weeks after surgery).
What other surgical procedures are commonly performed for glaucoma?
Glaucoma drainage devices or implants are commonly used now in the treatment of many types of glaucoma. These devices consist of a small tube that is placed into the front part of the eye. This tube drains to a “plate” which is sutured to the eye well back from the edge of the cornea. The whole device is attached to the eye under the mucous membrane of the eye surface and thus is generally hidden from view.
