The drainage system
Much of the mechanical part of seeing takes place with structures in the front part of the eye, called the anterior chamber. You can think of the cornea as the crystal of a watch and the iris as the face of the watch. The space between them is filled with a watery fluid called aqueous humor. This fluid bathes and nourishes the cornea and lens, which have no blood supply of their own.
The aqueous fluid is pumped into the eye from the ciliary body just behind the iris where it is produced. The fluid circulates around the lens, through the anterior chamber and drains out through the trabecular meshwork, the tiny sponge-like filtering system located where the cornea and iris meet.
After passing through the trabecular meshwork, the aqueous humor passes through the Schlemm’s canal, a minute duct that runs in a circle just beneath the border of your iris and the white of your eye (the sclera)., and is absorbed into the bloodstream.
The health of the eye depends on a continuous process of production, flow, and drainage of this aqueous fluid.
Potential problems in the optical stage – drainage
This fluid inside the eye plays another important role, one critical to glaucoma: the fluid provides the necessary pressure inside the eye, known as intraocular pressure (IOP), to maintain the shape of the eye. If too much fluid is produced or the drainage system does not adequately remove the used fluid, pressure builds up in the eye and the eye expands, much like a balloon. When the eye expands with the increasing pressure, it gives way at its most vulnerable point, which is where the optic nerve exits the eye.
The optic nerve is thin and vulnerable where it leaves the retina, and so the result of the increased intraocular pressure can be damage and then death to the axons of the nerve cells.