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Glaucoma
Written by Dr Caroline MacEwen, consultant ophthalmologist
What is glaucoma?
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:
There are other types of glaucoma which are much rarer and can be caused by a variety of reasons:
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?
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
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
How does the doctor make a diagnosis?
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.
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.
The symptoms of other types of glaucoma vary, depending on the underlying cause.
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