Primary open angle glaucoma (POAG) is characterised by an open and normal appearing anterior chamber angle, with no other underlying disease. POAG is the most common form of glaucoma. It may be associated with raised intraocular pressure (IOP) but this is not always present. Some patients with POAG have normal pressure glaucoma.
The defining feature of primary open angle glaucoma is that there is no underlying disease attributable to the raised intraocular pressure. If there is an identifiable underlying cause for the raised intraocular pressure, this is termed secondary glaucoma.
Another form of glaucoma where the intraocular pressure is within normal limits is known as normal tension glaucoma.
In primary open angle glaucoma, there is damage of the optic nerve head due to loss of primary ganglion cell axons.
The risk factors for primary open angle glaucoma include:
Aqueous humour is produced by the ciliary epithelium in the posterior chamber of the eye. It passes through the pupil into the anterior chamber and drains in the anterior chamber angle, also known as the iridocorneal angle.
There are two main drainage pathways for aqueous humour: