Glaucoma Surgery
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
cycloablation, a metal probe, frozen with liquid nitrogen, or a diode laser probe is
placed on the outside of the eye in the location of these ciliary processes. The cold or
laser 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.
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