Updated April 16, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

When topical or oral medications, or even laser surgery, no longer control glaucoma adequately, a type of glaucoma surgery called a trabeculectomy may be the next step. Sometimes referred to as filtration surgery, a trabeculectomy is performed by an ophthalmologist in an operating room. A trabeculectomy is the most common glaucoma surgical procedure performed when topical eye drops or glaucoma laser surgery does not reduce eye pressure enough.

How Is Trabeculectomy Surgery Performed?

During a trabeculectomy, an ophthalmologist will remove a small piece of tissue from the drainage canal in the angle of your eye, where the cornea meets the iris. The new drainage hole creates a pathway that leads out of the eye and just under the sclera, the white outer covering of the eye. The thin layer of tissue over this drainage canal creates a space where fluid can flow, forming a slight bubble or elevation underneath the upper eyelid, known as a bleb. After the fluid flows into the bleb, the fluid is re-absorbed by vessels, which allow the body to carry the fluid away.

What Happens After Trabeculectomy Surgery?

After undergoing a trabeculectomy, you may experience slight discomfort or have a sandy, gritty feeling in your eye for a short time. Your recovery period will probably be between six and eight weeks. Your surgeon will examine the bleb several times during your post-operative period and will closely monitor your eye pressure. If the pressure is not low enough, it could be that the drainage canal has scarred shut, preventing proper outflow.

In this case, sutures and stitches may be adjusted with a laser to allow for better outflow. Medications will also be adjusted during this time. The success of the surgery will depend on your own rate of healing.
A few things to keep in mind while healing:

• Your surgeon will recommend that you sleep with a special eye patch to protect the eye during the night. This is worn from one or two weeks to a month after surgery.
• You will be instructed to use antibiotic and steroid eye drops to prevent infection and speed healing for a short while after surgery.
• Avoid straining very hard after surgery, as this can increase eye pressure.
• Avoid strenuous activities for the first couple of weeks.

What Complications Are Associated with Trabeculectomy?

• Unsuccessful outcome: One complication is that surgery does not adequately lower eye pressure. A trabeculectomy has a 65% to 70% success rate. People who do not receive 100% success may still have some significant reduction in eye pressure, but just not enough to eliminate the need for topical eye drops. Trabeculectomy surgery may be repeated, but secondary surgery has a higher failure rate than primary surgery.
• Hypotony: Hypotony is a condition in which eye pressure may fall too low. Low eye pressure is unhealthy and can cause choroidal effusion or retinal detachment.
• Infection: Because the bleb is formed with thin tissue, infection is always a concern. Your doctor will prescribe antibiotic eye drops to help prevent infection. Remember to wear goggles while swimming and limit the use of contact lenses. If you experience reduced vision, eye pain, redness or discharge after having a trabeculectomy, contact your doctor immediately.

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1. American Academy of Ophthamology. Primary Open-Angle Glacoma, Limited Revision (Preferred Practice Pattern). San Francisco: American Academy of Ophthalmology, 2005.
2. Allingham RR, Damji K, Freedman S, Moroi S, Shafranov G. Filtering Surgery, Shield’s Textbook of Glaucoma, 5th Ed. Lippincott Williams and Wilkins, p.568-609, 2005.