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Definition
Glaucoma is a group of diseases which
damages the optic nerve. The optic nerve carries images from the
retina to the brain enabling us to see. In some types of glaucoma,
increased pressure inside the eye affects the delicate tissues of
the optic nerve. Glaucoma damages nerve fibers, causing blind spots
to develop. Often people don't notice these blind areas until much
optic nerve damage has already occurred. If the entire nerve is
destroyed, blindness results. It is for this reason that glaucoma is
known as “the thief of sight”.
Glaucoma is the leading cause of irreversible blindness in the world
(67 million affected), especially in older people. Early detection
and treatment by your ophthalmologist are the keys to preventing
optic nerve damage and blindness from glaucoma.
The peripheral visual field loss in
glaucoma
What Causes Glaucoma?
Mechanical compression and/or decreased blood flow of the optic
nerve associated with other factors can lead to glaucoma. Although
high eye pressure sometimes leads to glaucoma, as many as 50% of
people with glaucoma have "normal" eye pressure.
What Are The Different Types Of Glaucoma?
The main groups are:
1. Chronic glaucoma, e.g. primary open angle glaucoma (POAG)- this
is the commonest form and leads to a progressive, painless loss of
vision
2. Acute glaucoma- this causes severe pain associated with a red eye
and a sudden increase in eye pressure. It warrants emergency
treatment
3. Normal-tension or low-tension glaucoma- the optic nerve suffers
damage with the resulting visual field loss even though normal
intraocular pressures are maintained (between 10-21mmHg of
pressure). It is believed that poor blood flow to the optic nerve
causes this condition.
4. Exfoliation syndrome is a common form of open angle glaucoma that
results when there is a build-up of abnormal, flakey material on the
lens. It is commoner in the elderly and in Northern Europe. This
material and pigment from the back of the iris can block the
drainage system of the eye, causing increased eye pressure. This
form of glaucoma responds well to laser (*link to laser treatment
below please*) treatment.
5. Pigmentary glaucoma is a condition typically affecting young,
nearsighted (myopic), Caucasian males. There is a release of pigment
particles into the drainage system of the eye causing blockage,
leading to an increase in eye pressure. This form of glaucoma
responds particularly well to laser (*link*) and surgery (*link*).
6. Congenital glaucoma- present at birth and very rare.
Symptons
In most cases, damage to the optic nerve
in glaucoma can occur without any symptoms. However, the presence of
the following warning signs, indicates that you need a thorough
examination by an eye doctor:
- Family history of glaucoma
- Loss of peripheral (side) vision
- Blind spots
- Need for frequent changes in glasses
- Difficulty in adjusting to a dark
room
- Blurred vision
- Sore, reddened eyes
- Appearance of halos or rainbows
around lights
- Severe headaches, nausea and eye
pain in rare cases
The symptoms described above may not
necessarily mean that you have glaucoma. However, if you experience
one or more of these symptoms, contact your eye doctor for a
complete examination.
How Is Glaucoma Detected?
Regular eye examinations by your
ophthalmologist are the best way to detect glaucoma. Your
ophthalmologist will measure your intraocular pressure (tonometry);
inspect the drainage angle of your eye (gonioscopy); evaluate any
optic nerve damage (ophthalmoscopy); test the visual field of each
eye (perimetry). Optic nerve photography and visual field testing
are performed at regular intervals to monitor the effects glaucoma
has upon the optic nerve and the person's overall vision. The
information from these tests provides an indication of the
effectiveness of the treatment being used and whether stronger
measures may be necessary. Not all these tests are necessary for
every person, or at every visit. The object is to determine if
glaucoma damage has increased during the time between your visits.
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Tonometry
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Gonioscopy |
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Optic nerve head examination using
latest scanning laser ophthalmoscope (SLO) technology
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Perimetry- automated visual field
measurement with Humphrey Visual Field Analyzer |
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Who Is At Risk For Glaucoma?
High eye pressure is the most important risk factor, but alone does
not mean that you have glaucoma. Your ophthalmologist will put
together many kinds of information to determine your risk for
developing the disease. The most important risk factors include age,
myopia, African-Caribbean ancestry, family history of glaucoma, past
injuries to the eyes, or a history of severe anaemia or shock
requiring blood transfusions. Your ophthalmologist will consider all
these factors before deciding if you need treatment for glaucoma, or
whether you should be monitored regularly as a glaucoma suspect to
detect the early signs of damage to the optic nerve.
“Cupping”- damage to the optic
nerve head (optic disc) causing enlargement of central cup (pale
area
Treatment
The treatment for glaucoma depends upon
the nature and severity of each case. As a rule, glaucoma cannot be
cured, but it can be controlled. Eye drops, tablets, laser treatment
and surgical procedures are used to prevent or slow further damage
from occurring. With any type of glaucoma, periodic examinations are
very important to prevent vision loss. Because glaucoma can worsen
without your being aware of it, your treatment may need to be
changed over time.
Topical medication- drops
Treatment with drops to reduce eye pressure is a proven method of
preserving vision in glaucoma.
There is a wide variety of drops on the market so that a large range
of different glaucoma conditions and patient preferences can be
addressed.
The latest group of drops is the Prostaglandin analogues (e.g.
Xalatan, Travatan, Lumigan), which are very effective and taken only
once in the evening.
Side-effects from some eye drops may include a stinging sensation,
red eyes, blurred vision, headaches, reduction in pulse and heart
rate or wheezing. Side-effects from pills may include tingling of
fingers and toes, drowsiness, loss of appetite, bowel
irregularities, kidney stones, anemia or bleeding.
Laser Surgery
Laser surgery treatments may sometimes
be effective alone or as additional therapy to drops.
- Trabeculoplasty is laser treatment
to encourage drainage to reduce pressure within the eye when
treating open-angle glaucoma.
- Selective Laser Trabeculoplasty (SLT)
- this is an advanced technology and promotes drainage of fluid
without damaging the delicate tissues of the eye.
- Iridotomy is laser treatment to
create tiny holes in the iris to prevent obstruction of fluid
outflow.
- Cyclodiode laser- a very effective
and safe way of reducing eye pressure long-term in moderate to
advanced cases of glaucoma. It is performed in the operating theatre
under local anaesthetic as a day case procedure.
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The SLT Laser
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Cyclodiode laser
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Operative Surgery
This is the best way of achieving a
low eye pressure for a long time. When operative surgery (trabeculectomy
or glaucoma drainage tube insertion) is needed to control glaucoma,
your ophthalmologist will use miniature instruments under
microscopic viewing to create a new drainage channel for the aqueous
fluid to leave the eye. The new channel helps to lower the pressure
inside the eye. Complications of glaucoma surgery are rare, but as
with any surgery they can occur. Surgery will be recommended only if
your ophthalmologist feels that it is safer to operate than to allow
optic nerve damage to continue.
- The procedure can be performed
either as an in-patient or day-case procedure
- Local or general anaesthetic can
be used
- The latest anti-scarring drugs are
used to preserve the function of the new drainage channel for
longer
- You will stop using your glaucoma
drops, but will start using antibiotic and anti-inflammatory drops
for a short period of time while the healing process occurs
- Careful post-operative follow-up
with the ophthalmic surgeon will ensure that the eye pressure is
well controlled
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