Definition and Overview

Also known as filtration glaucoma surgery, trabeculectomy is an invasive procedure that involves creating a different drainage site for the aqueous humor to reduce the buildup of intraocular pressure.

Aqueous humor is the transparent fluid produced by the ciliary body that travels through the anterior chamber and into the trabecular meshwork before it is drained. It is responsible not only for nourishing the parts of the eye that do not have a blood supply, but it also regulates eye pressure. When the fluid doesn’t flow properly, it accumulates and intraocular pressure builds up. If this progresses, a person is more likely to develop glaucoma, an incurable eye condition that damages the optic nerves leading to vision loss or blindness.

Trabeculectomy can be recommended as a primary treatment method or the last option in case all nonsurgical methods have failed to correct the condition. An ophthalmologist will make a decision by considering various factors including the severity or extent of the damage and the patient’s unique circumstances.

Who Should Undergo and Expected Results

In general, trabeculectomy is done on patients who are diagnosed with glaucoma.

There are many types of glaucoma and one of the most common is the chronic open angle, which progresses gradually. In fact, it may take up to 10 years before the first symptoms begin to appear. However, as in any type of glaucoma, the damage to the optic nerves is irreversible. What the ophthalmologist can do is to delay or prevent the progress of the disease by controlling intraocular pressure.

Some patients may also develop primary open angle, an acute condition wherein the pressure increases very rapidly in a short period of time. Although it’s rare, it is also more life-threatening.

Glaucoma can also develop as a consequence of other eye conditions like inflammation of the uveal tract or traumatic injury.

Often, patients with glaucoma are advised to use eye drops or undergo laser surgery, which is less invasive. If either or none of these work and the disease continues to progress, trabeculectomy is considered. However, it is the first form of treatment for severe cases.

The success rate of the procedure is high, and many patients are able to regulate their eye pressure after. However, the surgery doesn’t guarantee against future pressure build up, which means those who have high and uncontrollable intraocular pressure may need another or more rounds of trabeculectomy in the future.

How Does the Procedure Work?

The primary goal of filtration glaucoma surgery is to drain the aqueous humor by redirecting the fluid to another drainage site, which is often called the bleb. It is normally created in one of the uppermost regions of the eye’s surface so it remains “invisible” unless the patient purposely lifts his upper eyelids.

There’s no special preparation needed prior to surgery except that patients are advised against taking blood thinners at least a week before the procedure.

Trabeculectomy is usually done in a hospital or an eye clinic with a dedicated surgery room. Local or general anaesthesia is administered starting with an eye drop then an injection directly into the eyes. A drug called mitomycin C is applied on the eye’s surface to prevent scarring that can make the procedure less successful.

The surgeon then creates an opening by making a flap on the conjunctiva to access the sclera. A part of the trabecular meshwork is removed to create another opening in the eye’s front chamber. A part of the iris may also be removed to avoid plugging up the hole. All the flaps are put back and sewn with nylon sutures. The fluid that accumulates in the new opening is then absorbed into the bloodstream.

The procedure normally takes an hour and the patient can go home following a couple of hours of recovery. However, certain cases may require the patient to stay in the hospital overnight for close monitoring.

Possible Risks and Complications

Discomfort, swelling, droopy eyelids, and pain are fairly common immediately and within a few days or weeks after filtration glaucoma surgery, but their intensity should gradually disappear. In rare cases, more serious complications can occur. These include:

  • Bleeding inside the eye
  • Infection
  • Permanent scarring
  • Blurry or variable vision


  • Cassel, Gary H., M.D., Michael D. Billig, O.D., and Harry G. Randall, M.D. The Eye Book: A Complete Guide to Eye Disorders and Health. Baltimore, MD: Johns Hopkins University Press, 1998.

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