There are 2 main types of glaucoma.
Primary Open Angle Glaucoma
This is the most common form of glaucoma, in which the angle is open but the drainage channels become blocked over many years, leading to a gradual increase in eye pressure and gradual visual field loss. People with open angle glaucoma are usually unaware they have the condition as there are no symptoms such as pain, and loss of visual field is often not apparent until the disease has advanced. It is therefore vital that open angle glaucoma is detected as early as possible.
Open angle glaucoma cannot be cured, but once diagnosed can be treated and managed to maintain good vision. The most common treatment is using eye drops to lower the eye pressure. Occasionally, surgery or laser treatment is required.
Closed Angle Glaucoma
This occurs when the angle closes or narrows, preventing aqueous from getting to the drainage channels. The eye pressure therefore increases very quickly, causing symptoms such as severe pain around the eyes, headaches, nausea and haloes around lights. Closed angle glaucoma is an emergency and requires immediate treatment to lower the eye pressure. This is usually done by laser.
How is glaucoma detected?
Glaucoma can be detected during routine eye examinations at our practices.
There are various tests that can help us detect glaucoma:
The optometrist will carry out the tests that are appropriate for an individual patient.
Healthy optic nerve
The optic nerve in glaucoma
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1-Ophthalmoscopy
The optic nerve is examined by shining a bright light in the eye, or by using digital imaging. Any abnormalities can then be assessed and monitored. Observation of any changes to the optic nerve is probably the most important factor in detecting glaucoma.
2-Tonometry
Measuring the eye pressure – the surface of the eye is numbed then the pressure is measured using a probe. The device used to measure eye pressure is called a tonometer. This is a more accurate method of measuring eye pressure than the ‘puff of air’ test that some people are familiar with.
A high eye pressure increases the risk of developing glaucoma, although it is possible to either have glaucoma with normal pressures, or to have high pressures and not develop glaucoma.
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Measuring eye pressure
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3- Visual Fields
Measuring the visual fields assesses the function of the optic nerve; damage to the optic nerve due to glaucoma leads to a loss of visual field.
Our most sensitive visual field testing equipment – the Humphrey Visual Field Analyser, can detect even very early changes in the visual field. Visual field loss in glaucoma is progressive and if untreated will worsen, leading to eventual ‘tunnel vision’.
The normal visual field [enlarge]
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The visual field in advanced glaucoma [enlarge]
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4. Pachymetry
We have recently acquired a pachymeter at both practices.
This instrument allows us to more accurately measure the pressure inside the eye by taking into account corneal thickness, thereby giving us a truer indication of a patients’ risk of developing glaucoma.
Who is at risk of developing glaucoma?
Glaucoma is a major cause of irreversible blindness, affecting 2 in 100 people over the age of 40. Some groups are more at risk
than others of developing the disease.
Age
Glaucoma is much more common with increasing age. It is uncommon before the age of 40, but the risk of developing the disease increases after this.
Therefore we routinely carry out glaucoma checks on all patients over 40, and advise eye examinations every 2 years.
Family History
Having a first-degree relative (parent, sibling or child) with glaucoma increases the risk of developing the disease. Therefore eye examinations for this group of people are available on the NHS and are recommended every year.
Ethnic Background
Glaucoma is more common, and can develop sooner, in those people of Afro-Caribbean origin.
Short sight/ Diabetes
Those with high myopia or those who are diabetic may be at increased risk of developing glaucoma. |
