The aqueous is the clear fluid that gives the eye its pressure. Aqueous is produced in the ciliary body, flows through the pupil, across the front of the iris to the “angle” of the eye where it then drains through the trabecular meshwork to Schlemm’s canal.
If there is too much aqueous produced, or not enough aqueous draining through the trabecular meshwork, the fluid pressure in the eye will increase, causing open-angle glaucoma.
The angle is simply the opening to the trabecular meshwork between the iris and the cornea. In this diagram, the angle is “open”, meaning that the space is wide. If this space is narrow, obstructing the flow of aqueous to the trabecular meshwork, it is called narrow angle glaucoma.
Treatment for open angle glaucoma can either decrease the production of the aqueous (eye drops) or increase the outflow through the trabecular meshwork (eye drops and/or laser).