There are four main types of glaucoma.
A rare but serious developmental abnormality of the eye causing glaucoma.
There are several possible causes including inflammation, trauma, surgery and syndromes such as pigment dispersion and pseudo-exfoliation.These cause raised IOP and glaucoma.
Pigment dispersion syndrome (PDS) is when pigment is released from the iris into the anterior chamber (fluid filled chamber at the front of the eye) which may then lead to a blockage of the drainage canals, a rise in eye pressure and damage to the optic nerve. This is known as pigment dispersion glaucoma.
Pseudo-exfoliation (PXF) is a rare condition caused by a build-up of abnormal protein which may block the outflow of fluid, cause raised eye pressure and may lead to optic nerve damage.
Primary open-angle glaucoma (POAG)
This is the most common form of glaucoma. Ten percent of over 75 year olds will have some form of POAG. The drainage angle of the eye is damaged, preventing the correct amount of fluid from draining away, leading to a raised IOP and damage the optic nerve.
It tends to run in families, with raised intra-ocular pressure the biggest risk factor in POAG. However, glaucoma can occur in patients with “normal” intra-ocular pressure (normal tension glaucoma).
Other risk factors include age, corneal thickness, ethnicity, myopia (shortsightedness) and diabetes.
Primary angle-closure glaucoma (PACG)
This is a much rarer condition in the UK, which occurs when the drainage angle between the iris and cornea, through which fluid passes is unusually narrow and can becomes close off. When this occurs, the inner eye pressure rises sharply, causing pain, nausea, blurred vision and redness in the eye.
It also tends to run in families, with hyperopic (long-sighted) eyes more at risk. Women are three times more likely to suffer from closed angle attacks.