The anterior segment, which lies between the cornea and lens, is filled with a clear, watery fluid called the , or simply aqueous. After passing through the cornea, light enters the aqueous humor where it is refracted again towards the center of the eye. This refraction is due to the difference in density between the cornea and aqueous humor.
Aqueous flow from the posterior chamber to the anterior chamber.
The aqueous humor supplies nutrients and oxygen to, and carries metabolic waste and carbon dioxide away from, the lens and the cornea. The aqueous humor is the sole source of nutrients and oxygen for the lens, as well as the endothelium layer of the cornea. Therefore, proper flow is critical for the health of these structures.
The aqueous humor is continually being produced by the ciliary body in the posterior chamber and drained out of the eye through the trabecular meshwork and canal of Schlemm in the anterior chamber. About 1 to 2.5 microliters of aqueous humor are formed and drained each minute.
For ocular pressure to remain constant, the rate of drainage must also be 1 to 2.5 microliters per minute. This balanced formation and drainage system normally maintains a constant intraocular pressure.