Glaucoma is an eye disease that affects 2-3% of people over the age of 60. It is the second most common cause of blindness in the western world and the second leading cause of blindness worldwide after cataracts.
There may be no symptoms to glaucoma as it is often a silent disease slowly developing over time. It is often detected during a glasses assessment by a vigilant optometrist, or because a patient is aware of the risk and has chosen to have their eyes formally checked.
Early detection, through regular and complete eye exams, is the key to protecting your vision from damage caused by glaucoma.
If you have a question or would like to book an appointment, please contact our friendly specialist team on 0800 AKL EYES or email to email@example.com
Please visit the website of charitable trust Glaucoma NZ to learn more about their efforts in preventing blindness from glaucoma.
Glaucoma occurs when the intraocular pressure (IOP) within the eye is high enough to cause progressive damage to the optic nerve, resulting in vision loss.
A normal healthy optic nerve has about a million nerve fibres which come from the retina (the seeing membrane at the back of the eye). When glaucoma develops, these nerve fibres start to die off and if enough nerve tissue is lost, then the vision starts to be affected.
In the initial stages of glaucoma there is usually no noticeable change in vision but it has been estimated that during this time a patient can lose as many as half the nerve fibres in the eye and these cannot be regenerated.
Even when glaucoma deterioration does become more advanced, the loss of sight starts out in the peripheral part of vision and people are often unaware of it. Once it reaches the central vision and does become noticeable, glaucoma has already reached an advanced stage and cannot be reversed. While there is currently no cure for glaucoma, the condition can be controlled. Auckland Eye are specialists at supporting and treating those affected.
The causes of glaucoma include:
Normal eye - aqueous fluid is produced in the ciliary body, passes through the pupil and exits through the drainage angle
Closed angle glaucoma - the drainage angle is blocked and the aqueous fluid is unable to exit
There are a number of tests that can be performed to determine whether someone has glaucoma. These generally involve measuring the IOP, a test to measure peripheral (side) vision and assessments of changes in the optic nerve.
Tonometry measures the inner pressure of the eye providing an IOP reading. Anaesthetic eye drops are used to numb the eye and then the doctor or technician uses a special device (tonometer) to measure the eye’s pressure.
Gonioscopy is a painless eye test using a contact lens that checks to see if the drainage angle of the eye is normal.
This is a simple, quick and painless test to measure the thickness of the cornea. It is important to assess this as it can have a bearing on the accuracy of eye pressure measurements.
Thick Cornea + Normal eye pressure
Thin Cornea + Normal eye pressure
Average Cornea + Normal eye pressure
KEY: - = less risk, + = higher risk
4. Visual field testing
Computerised measurements of a patient’s peripheral vision are helpful to diagnose and to monitor glaucoma. During this test, the patient is asked to look straight ahead and indicate when they see a light appear in their peripheral vision. This test helps to draw a “map” of a patient’s vision and any related gaps.
5. Nerve fibre layer measurements
The thickness of the nerve fibre layer can be measured using a non-invasive imaging technique known as Optical Coherence Tomography (OCT). Like visual field testing, this can help in diagnosing glaucoma and also monitor its progression.
6. Optic nerve imaging
Obtaining baseline readings of the optic nerve, and repeating the tests regularly, is important as the doctor can then see if there are any changes over time. Photos and laser scanners are used to provide this information.
1. Primary open-angle glaucoma
This is by far the most common form of glaucoma and appears in two-thirds of all cases. In open-angle glaucoma the drainage area in the eye is open but not working properly and pressure slowly builds up, causing gradual loss of peripheral vision.
2. Normal tension glaucoma
This is where the pressure inside the eye is within the normal range but nerve damage still occurs in spite of this. This accounts for about 25% of glaucoma cases and is more common in Asian races and people who have migraine or blood circulation problems.
3. Angle closure glaucoma
This uncommon type of glaucoma is caused by a blockage in the pressure drainage system. It is the only type of glaucoma that can be painful and develops rapidly. Patients may notice a severe aching in the eye along with eye redness and blurring of vision. It can damage vision within a day or two so an urgent assessment is needed.
4. Secondary glaucoma
Secondary glaucoma can arise due to other eye problems such as inflammation, blood vessel blockages and trauma.
5. Congenital and juvenile glaucoma
Uncommon, this type of glaucoma can occur in babies, children or young adults and the treatment may be different from adult glaucoma.
Eyes should be examined regularly and people should be tested and screened for glaucoma in keeping with the following recommendations:
Anyone with risk factors should be tested every year or two after the age of 40. Community optometrists are in the best position to offer this sort of screening.
The aim of treatment is to reduce the pressure (IOP) inside the eye, which will reduce stress on the optic nerve and slow down or stop any further nerve damage. If the pressure is brought down to a satisfactory level, then the risk of visual field loss in reduced.
Glaucoma New Zealand is a non-profit organisation that provides support for New Zealanders with glaucoma. As a member you will receive regular newsletters with information about glaucoma and any new treatments that are becoming available. If you would like further information then please contact Glaucoma New Zealand:
Auckland Eye is an affiliated provider to Southern Cross Health Society for OCT measurements.
Auckland Eye - New Zealand Centre of Excellence for Eye Care