Surgery for glaucoma can be used as the initial treatment in some cases of glaucoma or it can be used after medical and/or laser treatment has turned out to be ineffective or inadequate. There are various types of surgical procedures that can be performed, all of which aim to lower intraocular pressure (IOP) by creating an alternative pathway for fluid drainage out of the eye.

Trabeculectomy

This procedure can be performed for practically all types of glaucoma, adult or pediatric, open angle or angle closure, primary or secondary. A tunnel-like pathway is created out of the eye’s own tissue. This new drainage pathway starts in the anterior chamber and ends under the conjunctiva, the transparent “skin” covering the sclera, forming a fluid pocket called a bleb. This allows fluid to exit the anterior chamber, bypassing the diseased or blocked anterior chamber angle, and be absorbed from the bleb.

The benefit of trabeculectomy is superior IOP control that is rarely achieved by medications or laser. Improved IOP control means lower IOP and a more stable IOP (fewer fluctuations). This leads to more effective prevention of further optic nerve damage. Usually, the need for IOP-lowering medications can be reduced or eliminated after the surgery.

Even the most perfectly performed trabeculectomy will fail if the eye does not receive proper post-operative care. The first 6-8 weeks after surgery are extremely critical and it is important to not miss any follow up visits and to take all post-operative medications (usually eye drops) as prescribed.

Because a trabeculectomy creates an unnatural pathway in the eye, the body’s natural healing response is to try to close the newly created pathway. Scar-preventing medications that were initially developed for preventing tumor cell growth (cancer) are often applied during the operation to reduce the healing response around the pathway. Sometimes, the eye doctor may also need to inject these medications under the conjunctiva several times during the first few weeks after surgery.

A trabeculectomy does not always last as long as we hope. It often happens that, as the years pass, the healing response of the body slowly takes over and the trabeculectomy loses its function causing the IOP to increase. When this happens medications may need to be added or the original surgical site may need to be opened either in the doctor’s office or in the operating room. Sometimes, another glaucoma surgery may be needed. This can be a new trabeculectomy or a different type of procedure.

The common complications of trabeculectomy already mentioned above are early failure and late failure. Other complications include development of a cataract or accelerated progression of an existing cataract, excessive fluid flow out of the eye (an extremely low IOP can be just as unsafe as a high IOP), and late infection of the surgical site called blebitis that, if untreated, can lead to a severe internal eye infection called endophthalmitis. Patients who have had a trabeculectomy have about a 5% risk of having blebitis at some point during their lifetime so they must consult their eye doctor immediately if they develop a red eye. As with surgery in any other part of the body, surgical infection or severe bleeding during the surgery can also occur.

Trabeculectomy may be combined with cataract surgery for glaucoma patients who also have a significant cataract.

Glaucoma implant surgery

In certain cases, simple glaucoma surgery (trabeculectomy) may be highly likely to fail. In these cases, a device that shunts fluid from inside the eye to the space under the conjunctiva may need to be implanted into the eye. These are called glaucoma implants or glaucoma drainage devices (GDDs) and there are several different types available. Because of the expense of the devices and the complications that they can cause, they are usually reserved for special and difficult cases.

Childhood glaucoma procedures

Because of the early developmental stage of children’s eyes, there are glaucoma surgical procedures that can be performed in children that are not possible in adult eyes. These include goniotomy, trabeculotomy, and combined trabeculectomy-trabeculotomy. In general, these procedures are more successful at lowering IOP than the usual trabeculectomy in children. As much as possible, these childhood glaucoma procedures are preferred over the usual trabeculectomy. However, the choice of procedure ultimately depends on the condition of the eye because some conditions can make certain procedures impossible or too risky. Childhood glaucoma procedures are best performed by a glaucoma specialist with experience in treating children.

References:

1. Ritch R, Shields MB, Krupin T (Eds). The Glaucomas, 2^nd Edition. St. Louis, Missouri, USA, 1996, Mosby-Year Book, Inc.
2. Epstein DL, Allingham RR, Schuman JS (Eds). Chandler and Grant’s Glaucoma, 4^th Edition. Baltimore, Maryland, USA, 1997, Williams & Wilkins.
3. South East Asian Glaucoma Interest Group. Asia-Pacific Glaucoma Guidelines. Sydney, Australia, 2003-2004, SEAGIG.
4. European Glaucoma Society. Terminology and Guidelines for Glaucoma 2^nd Ed. Savona, Italy, 2003, EGS.