Glaucoma Surgery - Glaucoma: Eye Care

Content provided by the Faculty of the Harvard Medical School

Glaucoma surgery

If the maximum tolerated medication cannot control your eye pressure, your ophthalmologist may recommend glaucoma surgery. The doctor will discuss the reasons for recommending surgery, as well as its risks and benefits.

Surgeons can choose from several procedures for treating glaucoma, including laser surgery as well as conventional surgery. Some people do not respond to laser surgery. Still, most ophthalmologists will recommend trying laser surgery first because conventional surgery carries additional risks of hemorrhage, infection, and other potential problems.

Laser trabeculoplasty. This surgery improves drainage of fluid in open-angle glaucoma (see Figure 7). The ophthalmologist usually performs the procedure in his or her clinic, using a high-energy laser beam to burn tiny holes onto the surface of the eye's trabecular meshwork. The doctor makes about 50 burns over half of the trabecular surface, which allows fluid to flow more freely through the mesh and out of the eye.

Figure 7: Laser trabeculopasty for glaucoma If glaucoma cannot be controlled with drugs that reduce the intraocular pressure, a doctor may recommend laser trabeculoplasty. In this procedure, the surgeon uses a high-energy beam of light to produce small burns on the trabecular meshwork while viewing the eye through a prism. The procedure improves the flow of aqueous humor out from the eye. A slit-lamp microscope and a contact lens allow the ophthalmologist to get a detailed view of the angle where the iris, cornea, and sclera meet, and to focus the laser on the tissue.

Before the procedure, the ophthalmologist numbs the eye with drops that allow a special contact lens with mirrors to be placed on the eye. As you sit in a comfortable position at the slit lamp, the doctor applies the contact lens as your eye fixates on a target. You may see flashes of green or red light as the doctor focuses and fires the laser; there is no pain. The treatment takes less than half an hour. The doctor then checks the pressure in your eye before allowing you to go home. Prescription eye drops help reduce inflammation during your recovery. You will also use your regular glaucoma medicines and schedule several follow-up visits so the doctor can monitor your pressure. You may experience blurred vision and sensitivity to light for a day or two after the operation, but you should not feel any discomfort.

While trabeculoplasty is often helpful, the benefits may not be permanent. If it is only partly successful, the doctor may need to perform the procedure again on the other half of the trabecular surface. As the treatment effect wanes, within two to three years, you may need more medicines or one of the following forms of conventional surgery.

Selective laser trabeculoplasty. A procedure called selective laser trabeculoplasty (SLT), approved by the FDA in March 2001, offers an alternative to regular laser trabeculoplasty for open-angle glaucoma. The procedure uses a neodymium: YAG laser, which is thought to cause less damage to the trabecular meshwork than a regular argon laser. Studies have shown that SLT is effective and may be repeated safely many times. For now, this technology is considered an alternative to traditional laser trabeculoplasty, or may be used as a second procedure for those who've been treated already with laser trabeculoplasty.

Laser iridotomy. For treating acute closed-angle glaucoma, the doctor may suggest this technique even before prescribing medication. Using a laser, the surgeon creates a small opening in the outer edge of the iris to improve drainage of the aqueous humor from the posterior chamber to the anterior chamber (see Figure 8). The ophthalmologist can create this opening without making an actual incision in the eye, an advance over the older, prelaser procedure that required cutting out part of the iris by hand. Laser iridotomy often cures closed-angle glaucoma, making drug treatment unnecessary. In certain cases, however, topical medication or conventional surgery may be warranted.

Figure 8: Laser iridotomy for glaucoma The early stages of closed-angle glaucoma may be relieved by a laser iridotomy. The surgeon uses a laser to make a small opening in the edge of the iris to increase drainage of the aqueous humor from the posterior to the anterior chamber.

Conventional incisional surgery. Ophthalmologists use conventional surgery when medication or laser surgery is unsuccessful in treating chronic glaucoma or when acute closed-angle glaucoma has gone untreated and caused permanent damage. Conventional incisional surgery, also called filtering surgery, creates a new drainage system when the trabecular meshwork is either scarred or nonfunctional. In the most common procedure, the trabeculectomy, the surgeon opens a flap of tissue to form a new passageway so that fluid can drain from the anterior chamber of the eye to a space created beneath the conjunctival tissue under the upper lid. In another technique, used on scarred tissue, the surgeon implants a special plastic or silicone valve to provide drainage for fluid. The FDA has approved a number of drainage devices, and while they differ slightly in design, all appear to be effective.

Filtering surgery is successful in 80%–90% of patients, and the other 10%–20% can usually undergo further surgery, which typically leads to adequate improvement of pressure. Most patients can eliminate or reduce their use of glaucoma medication after surgery.

Filtering surgery is an involved procedure, so ask your ophthalmologist to refer you to an eye surgeon who has extensive experience and skill. The goal of this surgery is the development of a filtering bleb, an elevation of the conjunctiva of the eye. Filtering blebs may fail to form, may leak, and may be susceptible to infection. The surgery may also lead to blurred or decreased vision or the development of cataract.

Cyclodestructive surgery. When other methods of glaucoma control fail, a group of procedures collectively called cyclodestructive surgery may be useful. These surgeries share the common goal of destroying part of the ciliary body in order to decrease fluid production. Cyclodestructive surgeries were first done with diathermy (electric cautery) or cryotherapy (freezing), but now lasers are also used. In this procedure, the surgeon applies a probe, usually on the surface of the eye, and then uses a laser to destroy the secreting cells of the ciliary body. The overall success rate in controlling intraocular pressure is 60%–80%, and the risk of serious complications is relatively low. But many patients require more than a single treatment. The reason this therapy is not used sooner in glaucoma management is that even if pressure control is achieved, cyclodestructive surgery may cause inflammation that can interfere with vision and possibly produce cataract.

Last updated:	June 19, 2007