Primary open angle glaucoma (or chronic glaucoma)

This is the most common form of glaucoma. It is also known as chronic open angle glaucoma, chronic meaning long lasting or continuous.


The damage is usually caused by too much pressure within the eye (the intraocular pressure or IOP). The reason for the rise in pressure is probably because the drainage of fluid out of the eye isn’t working as well as it should. The increased pressure damages the optic nerve (the nerve of sight) by reducing the amount of blood that can get through the tiny blood vessels that supply the nerve and also by squashing the nerve itself.


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 has been done to their field of vision. This is because the characteristic damage occurs in the off centre parts of the field of vision. Both eyes work together and one eye 'fills in' for the other, so that blank patches are not noticed.


The eye specialist will carry out a range of tests in order to see how much damage has been done. These will include a visual examination of the nerve of sight where it leaves the eye (the optic disc), a check of the pressure in the eye (the intraocular pressure) and a test to map out any blank patches that may be found in the field of vision (these are the three screening tests for glaucoma). Other tests may include measuring the central corneal thickness and looking at the drainage angle in the eye (gonioscopy), to confirm the diagnosis. It is important for an accurate measurement to be made of your IOP and also to check the front parts of the eye to make sure that tthere is no physical obstruction of the drainage parts of the eye (the open angle).


Primary open angle glaucoma is usually treated with eye drops to reduce the pressure in the eye. Because you can never get back the vision that you have lost, it is very important to take your eye drops every day according to the instructions you will have been given. Every missed drop means a greater chance of a loss of vision. If the eye drops can’t control the pressure enough to stop the losses in your field of vision then different drops, laser or surgery might be recommended. Glaucoma is a lifelong condition – there is no cure, but treatment is very effective.

For someone diagnosed with early stage primary open angle glaucoma today, there is very little risk of losing useful vision providing you take your drops regularly and don’t miss your follow up appointments.

Don't forget that there is an important inherited risk for glaucoma. Tell close blood relatives so that they can be checked.

Order a copy of the Primary open angle leaflet, or download it from the site.