During trabeculectomy (sometimes also called filtration surgery), a new drainage opening is created to bypass the clogged drainage channels of the trabecular meshwork. The opening is partially covered with a flap of tissue from the sclera (the white part of the eye) and the conjunctiva (the clear thin covering over the sclera). This new opening allows fluid (aqueous humor) to drain out of the eye under the conjunctiva and form a little blister, or bubble, called a bleb. The bleb is located just under the upper eyelid, where it is not visible.
Rate of Success
This procedure has been shown to reduce IOP and the need for medical treatment in 60% to 85% of patients at one year. Trabeculectomy has a little lower rate of success in the following groups:
Children who have congenital glaucoma.
People who have difficult-to-control glaucoma in which new blood vessels grow on the iris (neovascular secondary glaucoma).
People who have had previous eye surgery.
Your doctor will discuss the risk and benefits with you, and explain what rate of success is expected.
What To Expect After Surgery
The surgery is outpatient, and done under local anesthesia. A patch and shield is placed on the eye overnight, and removed the next morning. A shield is usually taped over the eye at night for the first two weeks after surgery.
Right after surgery, antibiotics may be applied to the eye. Corticosteroid drops are usually applied to the eye for about 1 to 2 months after surgery to decrease inflammation in the eye, and prevent scarring.
Activity that might jar the eye needs to be avoided after surgery. People usually need to avoid bending, lifting, or straining for one to two weeks after surgery.
The most common problem after a trabeculectomy is scarring, which can close the new drainage opening too quickly. Mitomycin-C is commonly used during surgery to prevent scarring.
Some of the problems that may develop soon after surgery include:
Blurring of vision for a few days to weeks.
Bleeding in the eye; goes away on its own.
Extremely low pressures in the eye, which may result in blurred vision, cause a more rapid progression of cataract, or swelling in the back part of the eye (choroidal effusions).
Loss of central vision despite successful surgery. This can happen in those with severe endstage glaucoma with extensive visual field loss.
Infection in the eye.
Late complications after a trabeculectomy may include:
Droopy eyelid (a very slight droop of the eyelid is common).
Failure of the trabeculectomy from excess scarring. This is the most common cause of surgical failure. The surgically-created drainage hole begins to close and the pressure rises again. This happens because the body tries to heal the new opening in the eye, as if the opening were an injury. This rapid healing occurs most often in younger people, because they have a stronger healing system. Anti-wound healing drugs, such as mitomycin-C and 5-FU, help slow down the healing of the opening. Glaucoma drops can be restarted, and if needed, glaucoma filtering surgery can be repeated.
Tube-Shunt Surgery for Glaucoma
Tube-shunt surgery involves placing a flexible plastic tube with an attached silicone drainage pouch in the eye to help drain fluid (aqueous humor) from the eye. This type of surgery is usually done after a failed trabeculectomy. If a person already has or is likely to form scar tissue in the eye, this type of surgery may be done initially.
Tube-shunt surgery is outpatient, and is done under local anesthesia.
What To Expect After Surgery
For the first night only, the eyelid is usually taped shut, and a hard covering (eye shield) is placed over the eye. Corticosteroid and antibiotic drops are usually applied to the eye for several weeks after surgery to decrease inflammation in the eye and prevent infection. The eye may be sore for several days. A shield is worn over the eye at bedtime for the first one or two weeks after surgery.
How Well It Works
Tube-shunt surgeries are successful 50% to 80% of the time, dependent on glaucoma diagnosis and amount of previous surgery. There is usually a”high-pressure” phase two to four weeks after surgery, and glaucoma medications typically have to be restarted. Often, one or two glaucoma drops may be needed long term to augment the effect of the tube shunt.
Complications of tube-shunt surgery that may develop right after surgery include:
High pressure in the eye, causing the space in the front part of the eye (anterior chamber) to collapse (malignant glaucoma).
Inflammation in the eye.
Bleeding or blood in the eye (hyphema).
Softening of the eyeball due to fluid loss (hypotony).
Movement of the tube causing it to come in contact with the clear cover of the eye (cornea), the iris, or the lens.
Late Complications of tube-shunt surgery include:
Scar tissue forming around the device. The chances of this complication can be reduced if medicines, such as steroids, are used.
Infection in the eye.
Clouding of the cornea (if the tube comes into contact with it).
Eye muscle imbalance, resulting in double vision.
Types of Tube Shunts
A Baerveldt, Molteno, or Ahmed tube shunt may be used by your doctor, depending on the type of glaucoma, and the lowering of IOP needed.