Open-angle glaucoma

What it is

Glaucoma is an optic neuropathy in which retinal sensitivity is reduced and IOP is a risk factor. In the open angle form the obstruction is to aqueous drainage within the trabecular meshwork and its drainage into the Canal of Schlemm, while in the angle closure form the obstruction is to aqueous access. Open angle glaucoma is the common one (95%), angle closure the rare one (5%).

Glaucoma is first split by the angle and then by the cause:

• Open angle, primary: e.g. primary open angle glaucoma.
• Open angle, secondary: e.g. uveitis, steroid induced.
• Close angle, primary: e.g. primary angle closure glaucoma.
• Close angle, secondary: e.g. lens induced.

Causes and risk

Aqueous outflow is reduced by resistance of the trabecular meshwork in the open angle form, or by closure of the angle in the angle closure form. The ganglion cell layer is then lost, either from the pressure or from ischaemia. IOP is a risk factor for the whole process.