Trabeculectomy

Definition

Trabeculectomy is a surgical procedure that removes part of the trabeculum in the eye to relieve pressure caused by glaucoma.

Purpose

Glaucoma is a disease that injures the optic nerve, causing progressive vision loss. Glaucoma is a major cause of blindness in the United States. If caught early, glaucoma-related blindness is easily prevented. However, because it does not produce symptoms until late in its cycle, periodic tests for the disease are necessary.

Glaucoma is usually associated with an increase in the pressure inside the eye, called intraocular pressure (IOP). This increase occurs in front of the iris in a fluid called the aqueous humor. Aqueous humor exits through tiny channels between the iris and the cornea, in an area called the trabeculum. When the trabeculum is blocked, pressure from the build up of aqueous humor either increases rapidly with pain and redness, or builds slowly with no symptoms until there is a significant loss of vision. Trabeculectomy is the last treatment employed for either type of glaucoma. It is used only after medications and laser trabeculoplasty have failed to alleviate IOP.

Demographics

Glaucoma can develop at any age, but people over 45 are at higher risk. African Americans are more likely to develop glaucoma, especially primary open-angle glaucoma. Other factors, such as a family history of glaucoma, greatly increase the risk of contracting the disease. Diabetes and previous eye injury also increase chances of developing glaucoma.

Description

The procedure is performed in an operating room , usually under local anesthetic. However, some ophthalmologists give patients only a topical anesthetic. A trabeculectomy involves removing a tiny piece of the eye-ball,

During a trabeculectomy, the patient's eye is held open with a speculum. The outer layer, or conjunctiva, and the white of the eye, or sclera, are cut open (A). A superficial scleral flap is created and a plug of sclera and underlying trabecular network is removed (B). This allows the fluid in the eye to circulate, relieving pressure. The scleral flap is closed and sutured (C). The conjunctiva is closed (D). (

Illustration by GGS Inc.

)

Sometimes, an additional piece is taken from the iris so that anterior chamber fluid can also flow backward into the vitreous. This procedure is called an iridectomy .

Diagnosis/Preparation

The procedure is fully explained and any alternative methods to control intraocular pressure are discussed. Antiglaucoma drugs are prescribed before surgery. Added pressure on the eye caused from coughing or sneezing should be avoided.

Several eye drops are applied immediately before surgery. The eye is sterilized, and the patient draped. A speculum is inserted to keep the eyelids apart during surgery.

Aftercare

Eye drops, and perhaps patching, will be needed until the eye is healed. Driving should be restricted until the ophthalmologist grants permission. The patient may experience blurred vision. Severe eye pain, light sensitivity, and vision loss should be reported to the physician.

Antibiotic and anti-inflammatory eye drops must be used for at least six weeks after surgery. Additional medicines may be prescribed to reduce scarring.

Risks

Infection and bleeding are risks of any surgery. Scarring can cause the drainage to stop. One-third of trabeculectomy patients will develop cataracts.

Normal results

Trabeculectomy will delay the progression of glaucoma. In many cases, people still require medication to lower IOP.

Morbidity and mortality rates

Trabeculectomy is considered a safe procedure. Infection is a complication that could lead to more serious medical problems; however, it is controllable with eye drops.

Alternatives

Physicians will first try to lower IOP with glaucoma medications. Several types of eye drops are effective for this use. Sometimes a patient must instill more than one eye drop, several times a day. Compliance is very important when using these eye drops; missed dosages will raise IOPs.

Lasers are now used to treat both closed-angle and open-angle glaucoma. Peripheral iridectomy is used for people with acute angle-closure glaucoma attacks and chronic closed-angle glaucoma. The procedure creates a hole to improve the flow of aqueous humor.

Laser trabeculoplasty uses an argon laser to create tiny burns on the trabecular meshwork, which lowers IOP. The effects, however, are not permanent, and the patient must be retreated.

Transscleral cyclophotocoagulation treats the ciliary body with a laser to decrease production of aqueous humor, which reduces IOP.

A tube shunt might be implanted to create a drainage pathway in patients who are not candidates for trabeculectomy.

Resources

BOOKS

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.

Daly, Stephen, ed. Everything You Need to Know About Medical Treatments. Springhouse, PA: Springhouse Corp., 1996.

Sardegna, Jill, et. al. The Encyclopedia of Blindness and Vision Impairment, 2nd ed. New York: Facts on File, Inc., 2002.

Vaughan, Daniel, Ed. General Ophthalmology, 13th ed. Stamford, CT: Appleton & Lange, 1993.

ORGANIZATIONS

The Glaucoma Foundation. 116 John Street, Suite 1605 New York, NY 10038. (212) 285-0080. info@glaucomafoundation.org. http://www.glaucomafoundation.org

OTHER

"Glaucoma Filtration Procedure." EyeMdLink.com . [cited May 18, 2003] http://www.eyemdlink.com/EyeProcedure.aspEyeProcedureID=44� E; .

J. Ricker Polsdorfer, M.D. Mary Bekker

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

Ophthalmologists and optometrists may detect and treat glaucoma; however, only ophthalmologists can perform surgery. Ophthalmologists who are glaucoma subspecialists may have an additional two years of fellowship training.

The outpatient surgery is performed in a hospital or surgery suite designed for ophthalmic surgery.

QUESTIONS TO ASK THE DOCTOR

• Will IOP-lowering medication be needed after the surgery?
• How long will it take to determine if the surgery was a success?
• Can cataracts be treated in conjunction with glaucoma surgery?
• When will vision return to normal?