Surgeries
Glaucoma
Eye Disease
Surgery for open angle glaucoma
is considered in cases uncontrolled by medical treatment.
The most widely practiced operation is a "trabeculectomy".
The aim of this operation is to create a passage to
drain aqueous fluid from the front of the eye, through
the eye wall and into the space beneath the conjunctiva.
It can be performed both under general or local anesthetic.
The conjunctiva (the skin over the white of the eye)
under the upper eyelid is first opened and retracted
back. A small trap door is then fashioned in the sclera
(the wall of the eye) at the edge of the cornea. A hole
is then made under the trap door into the front of the
eye and a section of iris under the hole is removed.
The trap door is now sewn down, loose enough to allow
fluid out of the eye but not too loosely so that the
eye might collapse. Finally the conjunctiva sutured
back in place.
Generally it is a successful
operation, with good pressure control in up to 90% of
cases. Complications such as bleeding and excessive
drainage can lead to blurred vision, but in the majority
of cases this is transient and vision generally returns
to the level it was before surgery. Excessive scarring
under the conjunctiva can lead to drainage failure and
following surgery it may be necessary to release some
of the stitches holding the scleral trap door and/or
to use a fine needle to cut scar tissue to optimize
drainage. Drainage failure tends to be more common in
people of African origin, young patients, those who
have had previous eye surgery and those who have used
eye drops for many years. In such cases special chemicals,
called "anti-metabolites", can be used at
the time of surgery to reduce scarring.
In recent years a number of alternative
"non-penetrating" glaucoma drainage operations
have been developed such as "Deep Sclerectomy"
and "Viscocanalostomy". These techniques have
been designed to avoid making a full-thickness drainage
hole into the front of the eye in order to avoid some
of the early complications such as over-drainage and
bleeding that can occasionally occur after Trabeculectomy.
If patients are scheduled for a general anesthetic,
they must not eat or drink anything for six hours before
the operation. If they are to have only a local injection
or topical anesthesia a light meal up to four hours
before is acceptable. During the hour prior to surgery
the operated eye will be prepared for surgery and eye
drops will be administered - these are quite painless.
The operation may be carried
out under local or general anesthesia and unless there
is any specific medical reason for either one, the decision
is usually left up to the patients themselves. Most
trabeculectomy operations are now performed under local
anesthesia, thereby allowing patients to return home
soon after surgery. The administration of local anesthesia
causes little or no discomfort. Once the anesthetic
has taken affect, no pain will be felt, although there
may be a general awareness of movement of the eye.
The surgery usually takes
between 15-20 minutes.
Following the operation the operated eye has a plastic
shield placed over it before patients are accompanied
back to their cubicle/room where family or friends may
join them. Even when the operation is performed under
general anesthetic, most people find that they are ready
to leave hospital within a couple of hours of surgery,
although it is suggested that they rest quietly for
the remainder of the day. Before leaving patients are
asked to make an appointment for the first post operative
consultation and given eye drops containing cortisone
and antibiotics to administer for several weeks, whilst
the eye is healing.
Unless advised otherwise, patients
may begin eating normally at any time after the operation,
although it is sensible that the first meal is a light
one. All prescribed medications should continue to be
used after leaving the hospital.
Post-operative vision varies
from one patient to the next. Typically after trabeculectomy
some blurring of vision during the first six weeks is
not uncommon. The operated eye may appear red for the
first 3-4 weeks following surgery, but this is quite
normal and once the eye has settled down it will look
clear and healthy. There is usually little pain after
surgery although for a few weeks a gritty sensation
and bruised feeling is common. Stitches are used to
close both the scleral "trap-door" and the
conjunctiva. The deep stitches closing the "trap-door"
do not require removal unless excessive scarring causes
the drainage to fail, in which case they can be can,
lasered or removed to improve drainage. The surfaces
sutures closing the conjunctival are designed to fall
out by themselves after 4 to 6 weeks.
