Primary Glaucoma

Open-angle glaucoma is a slow-developing disease that causes damage to the optic nerve.

It is often symptomless, especially in the early stage.

Primary open-angle glaucoma (POAG), also known as ‘chronic open-angle glaucoma’ or just ‘open-angle glaucoma’.
It is the most common form of glaucoma.
It is estimated that approximately 2% of people aged 40+ have open-angle glaucoma and this rises to almost 10% in people over 80.

To understand primary open angle glaucoma, it’s useful to understand what glaucoma is and how drainage in the eye works.

Your eye pressure is controlled by watery fluid called aqueous humour, or just ‘aqueous’. Aqueous is made in a ring of tissue that sits behind the iris called the ciliary body. It then flows through the pupil and drains away through tiny channels called the trabecular meshwork.

The trabecular meshwork is found in the angle between the cornea and the iris (often called the drainage angle). In a normal eye, there is a balance between inflow and outflow of fluid, but in some eyes this balance is disturbed, and this causes the eye pressure to rise.

In most cases of POAG, the problem occurs due to the fluid outflow not working as well as it should. The eye can’t get rid of the fluid fast enough and the build-up results in increased eye pressure. The increase in pressure damages the optic nerve by reducing the amount of blood that can get through the tiny blood vessels and by pressing on the nerve itself.

Glaucoma cannot be cured, but it can be managed effectively. Sight loss resulting from glaucoma cannot be reversed, but with effective medical treatment, the damage can be minimised and disease progression slowed.

Open angle glaucoma is usually treated with eye drops that reduce the intraocular pressure. It is important to take your eye drops as instructed by your eye care professional.

Find out more about glaucoma eye drops

Who is at risk of primary open angle glaucoma

Anyone can develop primary open angle glaucoma but there are several risk factors that make the onset of glaucoma more likely. These include.

Age – Primary open angle glaucoma becomes more common with age. It’s uncommon below the age of 40 but the number of people with glaucoma rises from about two in 100 over the age of 40 to more than one in 10 for those aged 80+.

Ethnicity – People of African -Caribbean origin have about four times increased risk of primary open angle glaucoma when compared to those of a European origin.

Family history – There is at least a four times increased risk of developing glaucoma if you have a close blood relative with the condition (mother, father, sister, brother, child). If you have glaucoma, you should tell your relatives about the condition and encourage them to be tested regularly from age of 25

Other risk factors include myopia (short sight) and corneal thickness.

Glaucoma and your risk factors

Symptoms of primary open angle glaucoma (POAG)

POAG gives no warning symptoms in its early stages. There is no pain and in many cases, a person with this condition is completely unaware of the damage that is being done to their optic nerve.

This is because the typical damage occurs in the off-centre (peripheral) parts of the vision.

Both eyes work together and one eye ‘fills in’ for the other so that blank patches in your vision are not noticed.

Signs and Symptoms of Glaucoma

Treating primary open angle glaucoma

The aim of treatment is to reduce the pressure within the eye. This reduces pressure on the optic nerve and helps to stop further damage. Treatment is usually by eye drops. These help by reducing the fluid produced by the eye, increasing the drainage of fluid from the eye or both.

Laser is another common treatment and may be offered instead of, or in addition to eye drops.

If eye drops/ laser do not lower the eye pressure enough, surgical options are available.


“Glaucoma is the leading cause of preventable blindness in New Zealand, and about 50% of people with glaucoma don’t realise they have it.”

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How to get help

Resources to support and guide those navigating their way through glaucoma.

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Acute Angle Closure Glaucoma (AACG)
All About Eye Drops
Testing For Glaucoma


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