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(Saturday, 23rd Aug, 2014)
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Glaucoma

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What is glaucoma?

One of the most common causes of blindness worldwide, glaucoma is not in fact a single disorder of the eyes, but a range of conditions which causes the pressure inside the eye to become too high. If left untreated it can lead to damage of the optic nerve and a resulting loss of vision.

What causes it?

The eye is a very delicate organ which maintains its distinctive round shape as a result of the constant flow of fluid through it. This fluid, known as the aqueous humour, is secreted into the eye from an area behind the coloured part (the iris) and flows through the pupil before draining out of the eye through several microscopic channels.

Glaucoma develops when the flow of this essential fluid - which maintains the round shape of the eye and ensures that it does not become too hard or too soft - becomes obstructed and there is a build-up of pressure within the eye itself.

How quickly can it develop?

Two main types of glaucoma are seen at Irish ophthalmic clinics and these are: primary open angle glaucoma, also known as chronic simple glaucoma, and primary angle closure glaucoma, also known as acute glaucoma.

The first of these conditions - primary open angle glaucoma - is a slow, progressive condition, which can lead to blindness if left untreated. It occurs when the microscopic channels, which drain the aqueous humour out of the eye gradually become blocked.

Primary angle closure glaucoma, or acute glaucoma, occurs much more rapidly and can be both a frightening and distressing experience. It occurs when the flow of fluid inside the eye cannot pass through the pupil and this leads to a rapid rise in pressure within the eye.

Are there other types of glaucoma?

There are a number of other types of glaucoma besides the two mentioned above. Fortunately, they are much rarer conditions and are caused by a variety of reasons. They are:

  • A condition known as Uveitis or Iritis, which is caused by inflammation inside the eye.
  • Treatment with certain types of drugs, particularly steroids.
  • Glaucoma can develop as a result of a severe injury to the eye.
  • The growth of new blood vessels within the eye, which is caused by diabetic retinopathy.
  • It can develop from other rare abnormalities which affect the basic structure of the eye.

What are the symptoms of glaucoma?

Because primary open angle glaucoma is a slow, progressive condition, the patient may not notice any problem until the visual impairment has reached an advanced stage. The peripheral (or side) field of vision is the first to be affected in cases of primary open angle glaucoma, so there is no marked deterioration in the eyesight. It is only when the disease progresses to a stage where it damages the central vision, causing partial or total blindness, that treatment is usually sought.

To avoid this scenario, all patients over the age of 40 who undergo regular eye tests will be screened for primary open angle glaucoma. The pressure within the eye is checked, as is the nerve at the back of the eye and the field of vision. This underlines the importance of regular eye check-ups for the over-40 age group who are most susceptible to primary open angle glaucoma.

Acute glaucoma is characterised by the sudden development of very painful, red eyes with a blurring of vision. The patient may notice haloes around lights and will usually feel very unwell, perhaps suffering from a severe headache and vomiting. It is rarely seen in the under-50 age group and is more common in long-sighted people.

How is glaucoma diagnosed?

Making a diagnosis of acute glaucoma is a relatively simple process, as the patient will be suffering from a lot of pain and will have very red eyes and reduced vision. The pupil of the eye will normally be dilated and the clear window at the front of the eye (called the cornea) will usually be swollen, which causes the patient to see haloes around lights and to have blurred vision.

Because of the slow, progressive nature of primary open angle glaucoma, a diagnosis is more difficult. Any patient who is suspected of suffering from this condition will be referred to an eye specialist for a thorough examination. The pressure inside the eye will be checked as will the optic nerve behind the eye. Any damage to the optic nerve is usually referred to as "cupping" of the optic disc.

In addition to the above checks, a complete field of vision test will also be carried out.

Is there any treatment for glaucoma?

For primary open angle glaucoma, there are a number of different types of eye drops available. Some of these drops are not suitable for patients with heart conditions, and all of them must be prescribed by a qualified eye specialist. Ophthalmic patients should never share eye drops.

In some cases of glaucoma, surgery may be recommended. The surgical procedure used is called Trabeculectomy, and it allows fluid to drain from inside the eye to the outside. The only evidence that surgery has been performed on a patient is usually the formation of a small "blister" on the upper eyelid.

There are no major complications with surgery, except perhaps a temporary reduction in vision. However, a small number of patients suffer from recurring eye infections as a result of surgery.

In cases where there is severe blockage of the microscopic vessels leading from the eye, laser treatment may be used as a temporary measure to increase the flow of fluid from the eye.

Acute glaucoma is an emergency and requires urgent treatment by an ophthalmologist (a doctor who specialises in eyes). The need for treatment is urgent because of the potentially dangerous build-up of pressure in the eye. Treatment can take the form of eye drops, drugs given either intravenously or orally, laser surgery and sometimes a surgical procedure. An eye specialist will decide which particular course of action is most suitable, following detailed examination of a patient with acute glaucoma.

Can glaucoma be prevented?

The simple answer is no. Since glaucoma usually affects people in the 40+ age group, it is very important for everyone aged 40 and over to have a thorough eye examination every year. This will prevent the development of primary open angle glaucoma, as the onset of the condition will be identified at a routine eye check-up.

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