Glaucoma Surgery

By Marilyn Haddrill; contributions and
review by Charles Slonim, MD

All glaucoma surgery procedures (whether laser or non-laser) are designed to accomplish one of two basic results: decrease the production of intraocular fluid (aqueous humor) or increase the outflow (drainage) of this same fluid. Occasionally, a procedure will accomplish both.

Currently the goal of glaucoma surgery and other glaucoma treatment is to reduce or stabilize intraocular pressure (IOP). When this goal is accomplished, damage to ocular structures — especially the optic nerve — may be prevented.

No matter the treatment, early diagnosis is the best way to prevent vision loss from glaucoma. See your eye care practitioner routinely for a complete eye examination, including a check of your IOP. People at high risk for glaucoma due to elevated intraocular pressure, family history, ethnic background, age or optic nerve appearance may need more frequent visits to the eye doctor.

When Is Glaucoma Surgery Needed?

Depending on the type of glaucoma you have, different treatment options may be considered. Non-surgical options include the use of topical eye medications (glaucoma eye drops) or oral medications (pills).

Most cases of glaucoma can be controlled with one or more drugs. But some people may require surgery to reduce their IOP further to a safe level by improving the outflow or drainage of fluids. Occasionally, surgery can eliminate the need for glaucoma eye drops. However, you may need to continue with eye drops even after having glaucoma surgery.

Some recent studies indicate that a laser procedure known as selective laser trabeculoplasty (SLT) may be equally as effective as glaucoma eye drops for lowering internal eye pressure. This laser surgery might be considered a primary treatment, particularly for people who find it difficult to comply with the strict, regular schedule needed for administering eye drops.*

Another procedure called a trabeculectomy creates an artificial drainage area. This method is used in cases of advanced glaucoma where optic nerve damage has occurred and the IOP continues to soar. A third common option is a shunt, a device that a surgeon implants in your eye to improve fluid drainage.

Laser surgery for glaucoma may be required to open drainage channels, which helps reduce high internal eye pressure.

Laser Trabeculoplasty

To increase outflow of internal eye fluid, an ophthalmologist performs laser trabeculoplasty with a laser that creates tiny holes in the filtration angle of the eye, where the cornea and iris meet.

A newer procedure, selective laser trabeculoplasty, creates minimal heat damage to adjacent tissue, which generally means the procedure can be repeated safely. Laser trabeculoplasties are usually performed as an adjunct to a patient's ongoing eye drop therapy. Studies are now investigating whether SLT could be used routinely as a first-line therapy for treatment of open-angle glaucoma and other types of glaucoma, even before eye drops are used.

Trabeculectomy, Trabeculotomy and Goniotomy

Your eye doctor may recommend that a surgical incision be made into the eye's drainage system to create new channels for more normal flow of fluid. To accomplish this goal, a trabeculectomy involves partial removal of the eye's drainage system.

Trabeculectomy is the most common surgical non-laser procedure performed for glaucoma when the IOP is no longer controlled by eye drops, pills or laser trabeculoplasties.

A trabeculectomy creates a "controlled" leak of fluid (aqueous humor) from the eye, which percolates under the conjunctiva. A small conjunctival "bleb" (bubble) appears at the junction of the cornea and the sclera (limbus) where this surgically produced valve is made.

A trabeculotomy is the same as a trabeculectomy, except that incisions are made without removal of tissue.

A goniotomy typically is used for infants and small children, when a special lens is needed for viewing the inner eye structures to create openings in the trabecular meshwork to allow drainage of fluids.

Iridotomy and Iridectomy

In an iridotomy, a laser is used to create a hole in the iris to enhance the drainage passages blocked by a portion of the iris.

An iridectomy involves surgically removing a small piece of the iris that will allow a better flow of fluid in eyes with narrow-angle glaucoma.

Shunts and Implants for Glaucoma

Shunts or implants are small plastic devices that are surgically attached to the eye's surface. These devices have a tiny tube that is inserted into the eye through the hole that is made during a trabeculectomy. This allows a direct passageway for the aqueous to escape from the eye, with fluid dispersed through the implant. In this way, the aqueous fluid is diverted to bypass the eye's damaged filtration drainage canals.

Shunts typically are made of materials such as silicone or polypropylene. Some shunts are hollow tubes that improve drainage, while others have valves to shut off drainage.

Complications of these implants can include creating a pressure that is too low for the eye to function (hypotony). Implants also may be positioned too close to the front of the eye's surface, causing decomposition of the cornea. Tubes also may begin to erode through the eye tissues where they have been placed.

The SOLX DeepLight Glaucoma Treatment System combines a titanium sapphire laser with a gold shunt (shown at far left next to a quarter and at right inserted into an eye). At lower left and right are photos of a patient's trabecular meshwork before and after treatment.

Shunts with recent FDA approval or that are in clinical trials now are more sophisticated and less likely to cause complications, helping to expand safer options for glaucoma surgery. Examples include:

• Ex-PRESS Mini Glaucoma Shunt. This glaucoma treatment device, approved by the FDA in March 2002, shunts the aqueous out of the eye to a specific drainage area to potentially lower IOP. The system also has European approval (CE mark).
   
  The Ex-PRESS Mini Glaucoma Shunt was developed by Optonol, with U.S. headquarters in Kansas City. About the size of a grain of rice, the miniature shunt device is implanted between the anterior chamber where the aqueous humor is located and the outside of the sclera or white part of the eye, under the eye's surface membrane (conjunctiva). The aqueous bypasses the normal filtration angle of the eye that has been damaged by glaucoma. The aqueous then drains into a space under the conjunctiva.
• DeepLight Glaucoma Treatment System. SOLX (Boston) currently is undergoing FDA clinical trials with its DeepLight Glaucoma Treatment System that already has European approval (CE mark). The system involves combining titanium sapphire laser energy to open up the filtration angle of the eye (fluid drainage system) with the insertion of a hollow gold micro-shunt. The shunt creates an artificial channel to enable fluid drainage and relieve eye pressure. The laser or the shunt also can be used separately.
   
  The SOLX laser system, which received FDA approval in September 2008, is similar to selective laser trabeculoplasty (SLT), in that only pigmented cells are targeted, sparing adjacent tissue from potential heat damage. The DeepLight Gold Micro-Shunt operates differently from other types of glaucoma implants, because drainage is confined to the eye's interior with the idea of reducing surgical complications.

Nonpenetrating Glaucoma Surgery (NPGS)

Various innovative surgical techniques alter the eye's drainage channels, improving the flow of fluids with only minimal penetration into the eye. These surgical methods involve superficial incisions that do not penetrate the eye as deeply as, for example, a trabeculectomy. Proponents say fewer complications are likely to result from these less invasive procedures.

A deep sclerectomy involves a minimally invasive incision into the white of the eye (sclera), a portion of which is removed to create a drainage space for relief of eye pressure.

A new surgical method known as viscocanalostomy creates an opening for insertion of a highly pliable, gel-like material known as viscoelastic, which helps provide enough space for adequate drainage and eye pressure relief.

The Future of Glaucoma Treatment

Glaucoma specialists have differing viewpoints about the use of drug, laser and surgical intervention to control high IOP.

Some glaucoma specialists, for example, say that long-term costs of drug treatments involving eye drops can be an economic burden that may be offset with the use of laser treatments.

Others argue that treatments such as eye drops are far less invasive, are generally effective and have fewer risks of complications than laser or non-laser surgical approaches. Study results comparing long-term effectiveness of different treatments also vary.

*"Medications or Laser: Which One Is Best for Your Patient?" presentation by Barbara A. Smit, MD, PhD, Spokane Eye Clinic in Spokane, Wash., at the 2007 American Society of Cataract and Refractive Surgery conference in San Diego.

Judith Lee, Gretchyn Bailey and Dr. Vance Thompson also contributed to this article.

[Page updated January 2009]