Glaucoma is often categorised according to the appearance of the trabecular meshwork, which is the part of the eye through which fluid exits the eye. There are three types of glaucoma, which are described below.
1) Open angle glaucoma
This is the most common type of glaucoma. It usually affects both eyes and develops slowly so that loss of sight is gradual. There is no pain, redness of the eye or sudden change in vision. On examination, the trabecular meshwork appears normal but microscopically there is an obstruction within it.
2) Angle-closure glaucoma
Aqueous cannot gain access to the trabecular meshwork, usually because of blockage by iris tissue. It may present in two ways:
- There may be a gradual rise in eye pressure, which is painless and causes very gradual loss of sight.
- There may be a sudden increase in the pressure within one eye, causing the eye to become red and painful. Patients often notice blurred vision and see haloes around lights.
3) Secondary glaucoma
This type of glaucoma has an identifiable cause, being ‘secondary’ to another condition, eg inflammation inside the eye. As well as treating the glaucoma, the other condition must also be addressed.