Glaucoma is a disease that results from an excessive amount of fluid pressure within the eye. This can be caused by excessive fluid production or decreased fluid drainage. If the pressure gets too high, it can cause nerve damage and loss of eyesight. Most often, glaucoma can be treated with medicines. Glaucoma surgery becomes necessary when the pressure inside the eye cannot be controlled with medicines, alone.
All glaucoma treatments can be understood in terms of the balance between fluid coming into the eye and fluid going out of the eye. As an example, think of a bucket of water with a hole in the bottom. If you pour water into the bucket at the same rate that water is draining out of the hole, the water level will stay the same. You can decrease the water level by either pouring the water in more slowly, or by increasing the size of the hole in the bucket. In the eyeball, you can lower the pressure by either decreasing the amount of fluid going into the eye or by increasing the amount of fluid going out of the eye.
Fluid is produced inside the eye in structures called the ciliary processes. Surgery designed to decrease fluid production destroys some of these processes. This can be accomplished in different ways. In a technique called cyclocryosurgery, a metal probe, frozen with liquid nitrogen, is placed on the outside of the eye in the location of these ciliary processes. The cold destroys their ability to produce fluid. This same effect can be achieved by using a laser from the inside of the eye, treating the ciliary processes directly.
Most glaucoma surgery, however, is directed toward increasing the amount of fluid draining out of the eye. Fluid escapes the eye through a structure called the trabecular meshwork. A trabeculectomy is an operation in which an opening is made in the trabecular meshwork. More fluid can then drain out of the eye. The fluid is either channeled directly out of the eye or under a flap (trap door) in the wall of the eye. The fluid filters out of the eye and under the mucous membrane that covers the eye. In addition to traditional methods of surgery, lasers can now be used to make these openings from within the eye.
Laser trabeculoplasty is a common laser operation to lower the pressure in the eye. In this procedure, the laser is used to make small burns in the trabecular meshwork, allowing more fluid to drain from the eye.
In a more unusual type of glaucoma, called angle closure glaucoma, the laser is used to actually redirect the flow of the fluid inside the eye. A hole is made in the iris (iridotomy), allowing the fluid a more direct pathway to the trabecular meshwork.
Glaucoma operations are done when other methods of controlling glaucoma have failed. These operations have some risks associated with them, but the risk is usually less than the potential risk of losing vision from uncontrolled glaucoma.
PLEASE NOTE: The information contained on this system is not intended to supplant individual professional consultation, but is offered as a community education service. Advice on individual problems should be obtained directly from a professional.
Copyright, 1994. Richard E. Gans, M.D.
Last Modified: August 23, 1996