The Cause of glaucoma

A certain level of pressure is needed within the eye for it to keep its shape. This pressure is maintained by the flow of a fluid (aqueous humour) within the eye, and should not be confused with tears. A balance between the fluid entering and leaving the eye determines the pressure in the eye (the intraocular pressure).

Most cases of glaucoma occur because the flow of fluid out of the eye becomes restricted and the pressure within the eye rises. This pressure causes damage to the optic nerve.

In some eyes with glaucoma, the pressure is not high. In these cases it is thought that a poor blood supply or a weakness in the optic nerve structure may make the nerve susceptible to damage by normal eye pressure. This is known as normal tension glaucoma.

Some eyes can have moderately raised pressure but no signs of loss of vision or optic nerve damage and this is known as ocular hypertension.