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Glaucoma

Glaucoma refers to a number of conditions where the pressure in the eye is higher than normal. There are two main types, acute and chronic. Acute glaucoma is rare and involves a sudden rise in pressure associated with an inflamed eye, excruciating pain and blurred vision. Chronic glaucoma is much more common and not associated with pain. Glaucoma is rare under the age of 60.  Here, we will concentrate on chronic glaucoma..

Chronic glaucoma

Chronic glaucoma is a condition where the optic nerve (the cable that connects the eye to the brain) starts to degenerate. This is usually (but not always) associated with a higher than normal pressure in the eye.  If the optic nerve is thought of as a cable containing a million wires carrying the information from the retina, in glaucoma the wires start to die off in a specific pattern. Over a period of time this results in subtle changes in the visual field of the eye. Gradually tunnel vision develops and in extreme cases the vision in that eye is lost altogether. Once lost, the vision cannot be recovered and the eye remains blind. Glaucoma usually affects both eyes though not always to the same degree

Cause

GlaucomaThe eye maintained at a pressure by constant production of fluid (aqueous). This fluid circulates within the eye and than drains out through channels in the eye. It’s thought that these channels become silted up making it harder for the fluid to drain out. As a result the pressure in the eye rises. The rise is usually relatively small and does not cause pain. However over a long period of time this raised pressure can damage the nerve. Because there is no pain and the vision not noticeably affected, people with early glaucoma have no idea they have the disease. A person is more at risk from glaucoma as they get older and especially if a close relative has the disease.

Diagnosing glaucoma can be difficult. Three things are taken into account, the pressure of the eye, changes in the visual field and the appearance of the optic nerve. If all three are abnormal then the diagnosis is easy to make. Sometimes it is more difficult.

Ocular hypertension, normal pressure glaucoma and glaucoma suspects

Not everyone with high pressure develops glaucoma. If the pressure is much higher than normal they are quite likely to develop the disease, but not always. This state is called ocular hypertension (it is not related to blood pressure). If it is felt that the pressure may cause glaucoma in the future these people are started on treatment as a precaution, even though technically they don’t have glaucoma.

Some people develop damage to their optic nerve and visual field even if their pressure is normal. Their eyes have some particular sensitivity even to normal levels of pressure as they age. This is called normal pressure glaucoma.

The optic nerve can look like it has damage from glaucoma but in actual fact be perfectly healthy. Just to cause more confusion, the nerve can look healthy yet actually at the early stages of being affected by the pressure.

In very early glaucoma the visual fields tests may not be sensitive enough to pick up the very subtle visual field changes.

Where the diagnosis in uncertain, a person would be known as a glaucoma suspect. A surprising number of people fall into this grey area.  If the risk of developing glaucoma is felt to be low, they are often simply monitored. If the risk is felt to be higher they may be started on treatment as a precaution.

Diagnosis

Opticians will test all people over a certain age for glaucoma. Eye pressure is checked (air puff test) as are the visual fields together with the appearance of the optic nerves. If that person is thought to be at risk of glaucoma, they are referred to an ophthalmologist for a more detailed assessment. At the eye clinic more detailed tests are performed and all these are weighed up to assess a particular person’s risk of having (or developing) glaucoma. Those at very low risk will be discharged back to their optician. Those at higher risk will be monitored. Those at very high risk, or who are thought to have the disease will be started on treatment.

It is therefore important that all people get their eyes checked as they get older so the optician can test for glaucoma. This is especially so if there is someone in the family with the disease. Derby offers a full glaucoma assessment and treatment service. 

Treatment

For the vast majority of people requiring treatment, this will be in the form of drops. The drops reduce the pressure of the eye. Once the pressure is adequately lowered, the risk of the disease either developing or getting worse is much less. Modern anti-glaucoma drops are very effective but have to be used forever. They are not like an antibiotic where a course of treatment cures the disease. A person on treatment for glaucoma will be monitored for the rest of their life. They have their eye pressures, visual fields and optic nerves assessed on a regular basis, Pressure and optic nerve checks are performed about twice a year with a visual field test every one or two years. Uncontrolled glaucoma can be a blinding condition. It is very important that the drops are used and the condition monitored regularly.
If the condition is thought to be deteriorating, different drops are prescribed. In most cases this is all that is required. Occasionally for various reasons the drops stop working and these people end up having surgery for glaucoma. It is very rare for someone with controlled glaucoma to go blind from this condition.

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