What is glaucoma

What is Glaucoma?

Glaucoma is a group of related eye conditions that cause damage to the optic nerve. Located at the back of the eye, the delicate optic nerve transmits visual impulses from the eye to the brain. Injury or damage to the optic nerve can lead to loss of vision or even complete blindness. The loss of vision is usually gradual and may not be noticed immediately because it first affects peripheral or side vision.

Because vision loss from glaucoma is permanent, the need for it to be detected and treated as early as possible is critical. If not treated, glaucoma will cause progressive vision loss, normally in these stages:

  • Blind spots in your peripheral vision
  • Loss of peripheral vision (tunnel vision)
  • Complete blindness.

Glaucoma differs from macular degeneration which is characterised by progressive loss of central (straight ahead) vision, and cataracts, in which vision loss results from the lens of the eye becoming cloudy.

More about signs and Symptoms

Prof Helen Danesh Meyer explains basic facts about glaucoma

Top 10 Basic facts about Glaucoma that everyone should know from our virtual GNZ Glaucoma Patient Symposium 2020

Glaucoma is More Than Tunnel Vision

Depictions of what vision is like with glaucoma usually show a couple of children or scenery with darkness surrounding it, otherwise known as “tunnel vision.” But it’s not entirely accurate and until an individual reaches end-stage glaucoma the vision “loss” for the vast majority of glaucoma is just subtle peripheral blur. Well before dimming or darkness manifests you would not notice your sight loss in everyday life. Coupled with the fact that glaucoma is often an asymmetric disease (one eye is more affected than the other) means that the better eye covers for the worse eye.

In the example below, the children running onto the street may be completely missing from view in the later stages of glaucoma but the blurring of the black car on the right is probably more accurate. As a direct result, reaction times will be affected when driving and become slower.

Normal Vision
Early Stage Glaucoma
Later Stage Glaucoma

Uderstanding Glaucoma

Whats causes glaucoma?

Glaucoma is caused when pressure builds up inside the eye, damaging the optic nerve that connects the eye to the brain. Early diagnosis and treatment are critical to minimise or prevent loss of vision.

The level of elevated eye pressure that causes progressive damage to the optic nerve will vary between individuals. Some people can have high eye pressure without glaucoma (known as ocular hypertension) while other people can have normal eye pressure with glaucoma (known as normal tension glaucoma).

The eye is constantly producing a clear liquid called aqueous humour which it secretes into itself. This fluid nourishes the eye and holds the eye in shape. The fluid is then drained out through an area called the anterior chamber angle or drainage angle. If there is damage to the drainage angle, the rate at which the eye produces the aqueous humor then becomes greater than the rate the eye can drain it – causing high IOP in the eye.

This increased pressure starts to damage the optic nerve which is made up of approximately one million nerve fibres that connect the back of the eye to the brain. Damage to the cells of the optic nerve results in irreversible damage to your eyesight.

Different types of glaucoma

There are different types of glaucoma, with a range of characteristics and causes. Some of these include:

Dr Jesse Gale – Glaucoma With Normal Pressure

While most kinds of glaucoma involve elevated eye pressure, Normal-tension glaucoma (NTG), also known as low tension or normal-pressure glaucoma, is a form of glaucoma in which damage occurs to the optic nerve without eye pressure exceeding the normal range.

Primary Glaucoma

Either primary open angle glaucoma (POAG) or primary angle closure glaucoma (PACG)

Find out more

Secondary  Glaucoma

Including pigmentary, neovascular, uveitic glaucoma, trauma-related

Find out more

Developmental Glaucoma

Glaucoma in babies and children.

Find out more


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