From the Guidelines
The aqueous humor plays a crucial role in maintaining the eye's shape, nourishing avascular structures, and regulating intraocular pressure. The aqueous humor is a clear fluid that fills the anterior and posterior chambers of the eye, and its functions are essential for maintaining proper eye health. According to the primary angle-closure disease preferred practice pattern 1, the aqueous humor helps to maintain intraocular pressure, which is critical for the eye's shape and structural support.
Key Functions of Aqueous Humor
- Maintains intraocular pressure, giving the eye its shape and providing structural support
- Nourishes the avascular structures of the eye, such as the cornea and lens, by delivering oxygen, glucose, amino acids, and other nutrients
- Removes metabolic waste products from the eye
- Contributes to the eye's optical properties by maintaining appropriate spacing between ocular structures and providing a clear medium for light to pass through
- Continuously produced by the ciliary body in the posterior chamber and flows through the pupil into the anterior chamber, where it drains through the trabecular meshwork into Schlemm's canal
The production and drainage of aqueous humor create a dynamic flow system that helps maintain proper eye pressure, and disruptions in this system can lead to conditions like glaucoma, where increased intraocular pressure can damage the optic nerve 1. Understanding the functions of aqueous humor is essential for managing and treating eye conditions, and maintaining proper aqueous humor production and drainage is critical for preserving vision and preventing complications.
From the Research
Function of Aqueous Humor
- Aqueous humor is an important intraocular fluid responsible for the supply of nutrients to and removal of metabolic wastes from the avascular tissues of the eye 2.
- It is also indispensable for the maintenance of the optical properties of the eye 2.
- Aqueous humor plays a crucial role in maintaining retinal function, and its circulation is mediated by aquaporin-4 in the retina 3.
- The fluid dynamics of aqueous humor are frequently associated with the potentially blinding disease called glaucoma, and understanding its formation and regulation is paramount to develop rational and target-specific drugs for the treatment of glaucoma 2.
Formation and Circulation of Aqueous Humor
- Aqueous humor is formed mostly by active transport of ions and solutes across the ciliary epithelium 2.
- Three physiological processes contribute to the formation and chemical composition of the aqueous humor: diffusion (5%), ultrafiltration (15%), and active secretion (80%) 4.
- Aqueous humor leaves the eye by passive bulk flow via two pathways: the trabecular route and the uveoscleral route 4.
- The aqueous humor flow in humans follows a circadian rhythm, being higher in the morning than at night 5.
Regulation of Aqueous Humor Dynamics
- The individual parameters of aqueous humor dynamics may influence each other to maintain intraocular pressure (IOP) homeostasis 6.
- Central corneal thickness (CCT) is known to be associated with onset and progression of glaucoma and can potentially influence the individual parameters of aqueous humor dynamics that maintain IOP 6.
- The interplay between parameters of aqueous humor dynamics suggests possible autoregulatory mechanisms in the eye 6.
- The uveoscleral outflow pathway is relatively independent of the intraocular pressure, and the proportion of aqueous humor exiting the eye via the uveoscleral pathway decreases with age 5.