Glaucoma is a chronic, progressive deterioration of the optic nerve, the bundle of nerve fibers at the back of the eye that carry visual messages from the retina to the brain. Glaucoma is usually caused or worsened by pressure inside the eye (intraocular pressure) that is too high for the continued health of the optic nerve.
Managing Eye Pressure
Glaucoma treatment is aimed primarily at reducing the intraocular pressure to a safe level that will prevent or at least slow the nerve damage. Eye pressure is the major risk factor in the development of optic nerve damage from glaucoma and is the only factor that doctors can currently treat. In most cases, treatment consists of eye drops that either improve the drainage of fluid or reduce the formation of fluid inside the eye. When medication treatment has failed or is not tolerated, surgery is indicated in order to reduce the intraocular pressure.
Two Forms of Surgery
Surgical techniques include delicate laser or microscopic incisional methods. Generally, laser methods are tried before incisional surgery, although sometimes laser surgery is not appropriate for the condition or is not likely to bring the eye pressure low enough.
The microscopic incisional methods include trabeculectomy with mitomycin C or 5-fluorouracil application, glaucoma drainage device (or tube) implantation, cyclophotocoagulation, and ExPRESS microshunt implantation. In addition, there are newer, minimally invasive glaucoma surgeries such as the Trabectome or iStent that are combined with cataract surgery. These procedures are likely safer than traditional surgeries, but often do not lower the eye pressure enough for moderate to advanced glaucoma. Each surgery has its own special uses, advantages and disadvantages; the decision for which surgery to perform should involve a discussion between you and your ophthalmologist.
This article addresses the use of laser to lower eye pressure as a treatment for glaucoma and future articles will discuss various incisional surgeries.
Laser surgery is often used in open-angle glaucoma (the most common form of this eye disease) when medications do not work, are unlikely to work, or produce intolerable side effects. In some patients, laser surgery may be the first mode of therapy if eye drops are not practical or are unlikely to be used properly. For example, some patients do not want to use daily eye drops, either because they are difficult to instill in a consistent daily manner, have intolerable side effects, or are costly. For these patients, laser therapy may be their first choice. A patient and their doctor can weigh the risks, benefits, and side effects of laser treatment versus medications, and determine the best treatment to start with.
Laser trabeculoplasty is used in several types of open-angle glaucoma. It is used less commonly in angle-closure glaucoma after iridotomy has opened the drainage system or in mixed-mechanism glaucoma where both the open and closed angle forms of glaucoma co-exist.
Selective Laser Trabeculoplasty (SLT)
Selective laser trabeculoplasty (SLT) is a fairly recent advance. The laser used in this technique was especially developed for this job. The laser does not burn tissue, but rather vaporizes the pigment that may be affecting the cells in the drainage system. Since there are no burns, this laser technique can be repeated. The laser beam is aimed directly at the drainage system through a mirrored contact lens with the intent of improving the drainage of fluid out of the eye and thus lowering the pressure. While trabeculoplasty does not work in all patients, it is often used because of its relative safety. The success rate is about 60-70 percent in lowering the eye pressure by 20 percent.
What to Expect During the Procedure
Laser surgery has the advantage of being an in-office procedure with a very low risk for serious complications. Laser surgery generally does not require hospitalization or any change in daily activities. In most laser surgery, the eye is anesthetized with the same eye drops used for measuring the eye pressure. After the patient is set up in front of the laser, which looks like the typical examination microscope, a contact lens is temporarily placed on the eye. Laser surgery is not painful; however, the patient may feel an occasional pinprick type sensation. After the procedure is over, the contact lens will be removed and the surface of the eye is rinsed. Another eye drop may be given and the eye pressure will be checked again to ensure that it is not elevated. Sometimes the pressure rises transiently and rarely it may rise for a long period of time necessitating surgical intervention (which would have been necessary anyway if the laser option were not available).
Laser surgery to lower eye pressure can be very effective and safe, and has a definite place in the ophthalmologist's toolbox. In order to decide whether laser surgery is the correct treatment for you, a detailed conversation with your ophthalmologist will help you in making that decision.
Yvonne Ou, MD Assistant Clinical Professor of Ophthalmology Glaucoma and Cataract Surgery UCSF Department of Ophthalmology
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