What are Glaucoma Drainage Implants?
In some patients, particularly those with certain
types of glaucoma, the standard trabeculectomy
is known to be less successful in reducing intraocular pressure. A
surgical alternative in these individuals utilizes a glaucoma
implant or glaucoma drainage device.
These implants come in different shapes and sizes
(Figure 1). With each of them, a plastic tube is inserted into the
front of the eye behind, but not touching, the cornea. The tube is
like an artificial drain, and fluid passes through it to the outer
layers of the eye. It should be noted that the glaucoma implant is
not used to improve vision, but to lower intraocular pressure. In
this respect, it is completely different from the type of implant
which is used during cataract surgery.
Figure 1: Glaucoma implants come in
many shapes and sizes. A clear thin tube is placed into the
front part of the eye, and is connected to a reservoir (white)
outside the eye.
Glaucoma implants are not new. In fact, the idea
of controlling intraocular pressure with an external tube has been
tested for almost 100 years. Some of the materials that have been
tried include horsehair, silk, and tubes of gold. The long-term
success in the early days was poor and the complication rate was
quite high. However, with improved surgical techniques and the use
of plastics, glaucoma implants are now an acceptable and promising
therapy.
The patients most likely to benefit from this
procedure are those in whom a more standard glaucoma operation, such
as the trabeculectomy, is not expected to be successful. In general,
these are patients who have previously undergone eye surgery more
than once.
Occasionally, a glaucoma implant will be
recommended as an initial surgical procedure. In these patients, the
implant is necessary because there is expected to be extensive
scarring in the outer layers of the eye. Compared to the channel
made with trabeculectomy, the tube of the glaucoma implant is less
likely to become blocked by this scar tissue.
Glaucoma implant surgery is usually performed
with local anesthesia. There is little discomfort following surgery
except for a minor irritation. Most patients do not require
overnight hospitalization. After the operation, however, some eye
drops may be prescribed to ensure healing without infection.
Immediately after the surgery, intraocular
pressure may not be lower. Depending on how surgery is performed,
glaucoma medications may be continued during this period.
Glaucoma implants are usually placed in the area
underneath the upper eyelid (Figure 2). Unless the lid is pulled
back, neither you nor your family will notice it. With the upper lid
retracted, a white patch may be noted. This is a patch that covers
the tube and prevents irritation.
Figure 2: The clear tube is seen
through the cornea. The reservoir cannot be seen because it is
covered by the eyelid and outer portions of the eye.
Since glaucoma implants are used in patients with
more complicated problems, the success rate is slightly lower than a
standard trabeculectomy. However, in many patients, these implants
may be the best remaining available option.
Remember that the goal of glaucoma implant
surgery is to lower intraocular pressure and preserve vision. It
will not restore vision that already has been lost.
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10740 N. Central Expressway, Suite 300
Dallas, TX 75231
Office: 214-360-0000
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