Glaucoma is an eye condition that causes damage to the optic nerve, which transmits images to the brain. The eye needs a certain amount of pressure to maintain shape and size. However, increased fluid can put pressure on the optic nerve and cause damage.

If glaucoma is not treated, damage can progress, causing a loss of peripheral (or ‘side’) vision and may eventually lead to complete sight loss.

The eye produces a watery fluid called aqueous humour. Normally the fluid produced is balanced by fluid draining out, but if too much fluid is produced or if the drainage channels become blocked, then your eye pressure will rise. Too much pressure can damage the optic nerve.

image simulating a person's vision with Glaucoma


Glaucoma has no symptoms in the early stages so you may not notice any pain or noticeable change in your vision. In fact, 40% of your optic nerve can be damaged before you notice any loss of vision. That is why it is so important to have regular eye exams. A routine eye exam could pick up glaucoma before you notice any changes to your vision, and treatment may prevent any deterioration.

Glaucoma cannot be cured, and the damage caused is irreversible. Progression of the disease can be managed, and further deterioration of sight can be prevented if the condition is caught early.
Symptoms can include a reduction in contrast between objects and their background, night vision problems, and a loss of side vision. Glaucoma initially damages the peripheral (side) vision, eventually leading to tunnel vision. Central vision may not be affected until a later stage.


Types of glaucoma

Primary Open Angle Glaucoma

This is the most common form of glaucoma. The pressure in the eye rises slowly, without pain to warn of a problem, while the optic nerve is being damaged.

Normal Tension Glaucoma

In glaucoma, the eye pressure is not always high. Glaucoma can develop where eye pressure is within the normal range but the optic nerve becomes damaged. This is known as normal or low tension glaucoma. In fact, about 20% of all glaucoma patients have this form of the disease.

Angle Closure Glaucoma

This is a relatively uncommon type of glaucoma, which causes pain, blurring of vision and a red eye. Sometimes people may notice halos around street lights. This condition tends to occur over 24-48 hours, due to a very rapid rise in the eye pressure. Early treatment can reverse the problem and prevent long-term visual damage.

Secondary glaucoma occurs when another eye condition causes an increase in eye pressure. Babies can also have a rare eye condition called developmental or congenital glaucoma, which is caused by a malformation in the eye.