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.
When Is Glaucoma Surgery Needed?
Most cases of glaucoma can be controlled with one or more drugs, but in some cases surgery may be either preferred or more effective. Sometimes, surgery can eliminate the need for glaucoma eye drops. But this is not always the case.
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.
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.
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
Glaucoma shunts and stents are small devices that are surgically inserted into the eye to increase outflow of intraocular fluid and reduce high eye pressure. The devices create an alternative passageway for the aqueous to escape from the eye, bypassing the eye's damaged or clogged filtration drainage canals.
Shunts and implants that have gained FDA approval for glaucoma surgery in the U.S. or that currently are in clinical trials include:
Ex-Press Glaucoma Filtration Device.
Offered by Alcon, this is a miniature, stainless steel shunt for glaucoma surgery that has been FDA-approved since 2002. About the size of a grain of rice, the Ex-Press shunt is implanted under a small flap created in the sclera and allows the aqueous to bypass the damaged trabecular meshwork and exit the eye more freely to lower IOP.
iStent Trabecular Micro-Bypass. This shunt system from Glaukos Corp. is available in Europe for the treatment of open-angle glaucoma. The device also is commercially available in the United States and Canada for use in conjunction with cataract surgery for the reduction of IOP in patients with mild to moderate open-angle glaucoma. Made of surgical-grade titanium, the stent is placed in an internal area of the eye known as Schlemm's canal to re-establish a more normal flow of fluids within the eye. A next-generation version, called iStent Inject is currently being studied for use both in conjunction with cataract surgery and as a solo procedure.
CyPass Micro-Stent. The FDA approved the CyPass Micro-Stent (Alcon) in 2016. The device was designed to be inserted in the eye during routine cataract surgery for cataract patients who also have open angle glaucoma. Alcon voluntarily withdrew the CyPass Micro-Stent from the market in August 2018 after a five-year safety study showed potential corneal complications from the joint procedure compared with cataract surgery alone.
This tiny implant, by Ivantis, is roughly the size of an eyelash and is being tested in the U.S. for the treatment of primary open-angle glaucoma. The Hydrus procedure is less invasive than traditional glaucoma surgery and can be performed during cataract surgery using the same microsurgical incisions, according to the company.
Xen Gel Stent.
The Xen Glaucoma Treatment System (Allergan) lowers IOP by creating a subconjunctival drainage pathway. This collagen-derived, gelatin implant was FDA approved in November 2016. The procedure is usually coupled with cataract surgery, but it can also be performed as a stand-alone procedure.
This glaucoma drainage microshunt by Santen is made from a thermoplastic polymer called SIBS. The device is approved for use in Europe but is still awaiting FDA approval for use in the United States.
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.
Amy Hellem also contributed to this article.
Notes and References
One-year study results show reduced medication use, IOP after microstent placement. Ocular Surgery News. November 2012. Comparison of trabeculectomy and Ex-PRESS implantation in fellow eyes of the same patient: a prospective, randomised study. Eye. February 2012. "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.
Page updated September 2018