Aqueous humor and eye chambers

The aqueous humor (Latin: humor aquosus) is a fluid filling the anterior and posterior chambers of the eye and produced by the ciliary processes. The aqueous humor is loaded with nutrients. The aqueous humor supplies the cornea and lens, supports the eyeball, and maintain the intraocular pressure.

Structure of the aqueous humor

The aqueous humor originates from the plasma in the ciliary processes and is constantly secreted in the posterior chamber. The fluid flows between the zonular fibers, around the equator of the lens, then through the pupil and the iris into the anterior chamber. Within the anterior chamber, the aqueous humor circulates and then leaves the chamber through the iridocorneal angle in two possible ways. The first and main route is via the canal of Schlemm, while the other route - through the ciliary muscle, an alternative uveoscleral pathway.

A small amount of the aqueous humor possibly drains through the anterior surface of the ciliary body and then into the vorticose veins via the extracellular spaces and the suprachoroidal space. Some humor can also be absorbed into the choroidal veins and in the vorticose veins. A healthy human eye has 200 milliliters of aqueous humor.

Production of the aqueous humor occurs due to active transport by the unpigmented cells of the ciliary epithelium. The aqueous humor consists mainly of water. The aqueous humor is similar to plasma, but they differ in the concentration of electrolytes and other solutes. The humor has a very low concentration of proteins due to the blood-aqueous barrier.

Function of the aqueous humor

The aqueous humor supplies the cornea and lens with nutrients. It contains glucose, amino acids and has a high concentration of ascorbic acid. Apart from being the nutrient supplier, the aqueous humor also supports the eyeball and takes part in keeping its shape.

The aqueous humor is affecting and maintaining the intraocular pressure. The intraocular pressure under normal circumstances is 10-20 mm Hg. The pressure usually stays within the reference values but can slightly vary during each heartbeat and respiration. The rate of formation of aqueous humor, the rate of drainage of aqueous humor via the trabecular network, and the pressure in the episcleral veins are all responsible for keeping the intraocular pressure within the norm.

The chambers of the eye

As the aqueous humor passes through the anterior and posterior chambers, let's talk about them here.

Anterior chamber

The anterior chamber is a small space found behind the cornea and anterior to the iris, a part of the ciliary body, and a small area of the anterior surface of the lens. As mentioned before, the aqueous humor fills the anterior chamber. Chamber's volume is 0,2 milliliters. There is a corner between the cornea, sclera, ciliary body, and iris at the periphery margin of the chamber. The corner is called the angle. Within the angle is the trabecular meshwork for the drainage of the aqueous humor.

Posterior chamber

The posterior chamber is a small, 0,6 ml space between the iris in the front, the ciliary processes surrounding it, and the lens behind it. The posterior chamber also is filled with the aqueous humor and via the pupil has interaction with the anterior chamber.