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Written by Dr Caroline MacEwen, consultant ophthalmologist
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What is glaucoma?
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| Glaucoma is a range of conditions in which the pressure inside
the eye becomes too high. It is important that the doctor checks the back of
the eye for evidence of any damage. |
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Glaucoma is not one disorder but a range of conditions in which
the pressure inside the eye becomes too high. This results in damage to the
optic nerve at the back of the eye which can lead to loss of vision if left
untreated. Glaucoma is one of the most common causes of blindness worldwide.
How does glaucoma develop?
There is a constant flow of fluid through the eye. The flow into
and out of the eye is carefully monitored in order to ensure that the eye
maintains its round shape and does not become too hard or too soft.
This fluid is called the aqueous humour. It is secreted into the
eye from an area behind the iris (the coloured part of the eye) and flows
around through the pupil and drains out of the eye through several microscopic
channels.
Glaucoma usually develops when this flow of fluid becomes
obstructed and there is a build-up of pressure within the eye.
There are two main sub-groups of glaucoma:
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primary open angle glaucoma (formerly known as chronic simple
glaucoma) is a slowly progressive condition which occurs when the tiny
microscopic drainage channels gradually become blocked.
-
primary angle closure glaucoma (also known as closed angle or
acute glaucoma) occurs much more rapidly when the flow of fluid inside the eye
cannot pass through the pupil, causing a rapid rise in pressure inside the eye.
There are other types of glaucoma which are much rarer and can
be caused by a variety of reasons:
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inflammation inside the eye (uveitis or iritis).
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the growth of new vessels inside the eye, which may occur in
connection with
diabetes or after
blood vessel blockage at the back of the eye.
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treatment with certain medicines (eg
corticosteroids).
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following an eye injury.
-
other rare abnormalities affecting the structure of the eye.
Congenital glaucoma
It is very rare for children to be born with glaucoma but it is
a recognised condition. There is a tendency for this to run in families,
although it may occur in children with no family history of glaucoma at
all.
What are the symptoms of glaucoma?
Primary open angle glaucoma
The build up in pressure in this condition is very slow.
Therefore visual loss is gradual and patients often do not notice any problem
until there is evidence of severe visual impairment.
The peripheral (or side) vision is affected first and
therefore the eyesight is not obviously affected. These peripheral areas of
visual field loss increase until eventually the central vision is damaged
leading to blindness.
Because primary open angle glaucoma is not usually recognised
until it is advanced, people are screened for the condition as part of the
optician's routine examination when eye tests are carried out.
The optician will check the pressure, examine the nerve at the
back of the eye and test the field of vision if this is indicated. As primary
open angle glaucoma is rare in people under the age of 40, these screening
tests are usually only carried out after this age.
Primary angle closure glaucoma
In this condition the pressure inside the eye rises rapidly
and the eye becomes very painful. It is usually red and the vision becomes
blurred. The patient may notice haloes around lights.
There is often significant headache and occasionally the
patient feels very unwell and may even vomit. This condition is very rare in
patients under the age of 50 and is more common in people who are
long-sighted.
Other types of glaucoma
The symptoms of other types of glaucoma vary, depending on the
underlying cause.
How does the doctor make a diagnosis?
Primary open angle glaucoma
If there is any suspicion of primary open angle glaucoma, the
patient will usually be referred to an eye specialist (ophthalmologist).
The specialist will examine the patient's eyes in order
to accurately measure the pressure inside the eye and examine the nerve at the
back of the eye for any evidence of damage. This damage is usually described as
'cupping' of the optic nerve head (or optic disc).
A detailed computerised field of vision test will also be
carried out. Further tests and examinations may be required in order to ensure
that there are no other reasons for the glaucoma.
Acute angle closure glaucoma
This condition is usually diagnosed quite readily because of
the pain, redness and reduced vision. The pupil of the eye is dilated and the
pressure inside the eye is very high. The cornea (the clear window at the front
of the eye) is usually swollen, causing the haloes round lights and blurring of
vision.
Other types of glaucoma
A full examination of the eye will take place in anyone who
has suspected glaucoma in order to ensure that there are no other eye diseases
present.
How is primary open angle glaucoma treated?
There are a number of different types of
eye drops which are
available to treat primary open angle glaucoma:
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beta-blockers
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prostaglandin analogues
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adrenaline type drops (sympathomimetics)
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carbonic anhydrase inhibitors
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miotics (parasympathomimetics).
Beta-blockers
These drops are usually used twice a day. They reduce the
amount of fluid being secreted into the eye. These drops may need to be avoided
in people with
asthma or
heart disease as they
can be absorbed into the circulation, thereby causing problems in these areas.
Timolol (Timoptol)
is an example of a beta-blocker.
Prostaglandin analogues
This drop is used once a day in the evening. It works by
increasing the drainage of fluid out of the eye. The best recognised side
effect of this drop is that it can change the colour of the eye.
Latanoprost
(Xalatan) is an example of a prostaglandin analogue.
Adrenaline-type drops (sympathomimetics)
These are used twice a day and are generally well tolerated.
They reduce the amount of fluid secreted into the eye. Patients with heart
disease may be unsuitable for this treatment.
Dipivefrine
(Propine) or
Brimonidine
(Alphagan) are examples of adrenaline-type drops
(sympathomimetics).
Carbonic anhydrase inhibitors
These drops are used twice a day if used with beta-blockers,
or three times a day if used alone. They reduce the secretion of fluid into the
eye.
Dorzolamide
(Trusopt) is an example of a carbonic anhydrase inhibitor.
Miotics (parasympathomimetics)
These drops are usually used four times a day. They increase
the drainage of fluid out of the eye. These drops cause a small pupil which may
mean that they cause a reduction in vision.
They may give rise to headache. These drops were the original
drops to be used for glaucoma but are now less commonly used because of the
other newer drops as outlined above.
Pilocarpine (eg
Pilogel) is an example of a miotic (parasympathomimetic).
Other treatments
Carbonic anhydrase inhibitor tablets
In some cases these tablets are prescribed, but this is
usually only as a temporary solution as they can have many side effects such as
general nausea, tiredness, tingling of the fingers and, occasionally, if used
for a long time, a tendency to cause kidney stones.
Acetazolamide
(Diamox) is an example.
Laser treatment
This treatment is used to increase the flow of fluid from the
eye. The effect of this treatment may be temporary and therefore may not be
suitable as a long-term solution.
Surgical treatment
Many patients have surgery to treat glaucoma. The operation
used (trabeculectomy) allows drainage of fluid from inside the eye to the
outside of the eye. This type of surgery usually results in a small
'blister' on the eye which is usually positioned under the upper
eyelid. This type of surgery may include the use of anti-metabolite medicines
in order to make the success of the operation higher, although this may
increase the potential for complications.
Complications of such surgery include transient reduction in
vision after the operation, but this usually recovers. Long-term effects of
infection must always be considered.
How is closed angle or acute angle closure glaucoma
treated?
Treatment in this condition needs to be rapid. It takes the form
of drops, medicines given intravenously and orally, laser surgery and sometimes
surgical treatment.
Systemic medicines (carbonic anhydrase inhibitors)
As the pressure is very high inside the eye, this needs to be
dropped rapidly and therefore medicines such as acetazolamide are given rapidly
into the circulation through a vein. This should reduce the pressure quite
quickly.
Laser treatment
A hole in the coloured part of the iris is essential in order
to prevent this condition happening again. This hole is usually made using a
laser. Both eyes need to be treated, as although only one eye is usually
affected, the other eye will go on to develop acute closed angle closure if
left untreated.
Surgical treatment
Sometimes all the above treatments do not allow control of the
pressure and therefore a trabeculectomy (as outlined above in primary open
angle glaucoma) may be required.
How are other types of glaucoma treated?
A combination of drops, laser treatment and/or surgery may be
required depending upon the type of glaucoma.
Managing glaucoma
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Use all medication regularly as prescribed by your
ophthalmologist.
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Ensure that all follow-up appointments are kept.
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Make sure that you are clear about what type of glaucoma it is
that you have.
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Let your family know so that they can go and be screened for
the disease.
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If you need to start any new tablets for other conditions, make
sure your doctor is aware that you are using eye drops and what they
are.
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Always include your eye drops if you are asked about the
medications that you take regularly.
Activity
If picked up early enough, the vision should remain good and
there should be no restrictions in activity. There are strict guidelines
regarding visual standards for driving and people with glaucoma are advised to
let the DVLA know about the diagnosis. They will require regular fields of
vision testing to ensure that they remain fit to drive. After surgery there may
be limitations on activities in the short term.
Possible deterioration
Glaucoma, if not treated appropriately or picked up early
enough, may lead to blindness.
What can be done to avoid glaucoma?
Primary open angle glaucoma
There are no known methods of preventing this condition, but
it is vital that people over the age of 40 have their eyes regularly examined
as treatment in the early stages may prevent visual loss. It is impossible to
regain damaged vision if the early stages are missed. People with a family
history of glaucoma (especially parents or brothers and sisters) should be
especially vigilant, but anyone over the age of 40 should have a regular
examination.
Acute angle closure glaucoma
The acute attack with pain and reduction in vision may be
preceded by similar less severe attacks in the past. There may be a history of
haloes seen round lights, particularly in the evening, which tend to settle
overnight when the affected person goes to sleep. People with such symptoms
should seek medical advice.
Other types of glaucoma
Your eye specialist (ophthalmologist) may have given warning
that you are more susceptible to glaucoma if you suffer from one of the
conditions listed above.
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Last updated 01.04.2005
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