Highlights

• Aqueous humor is secreted by the nonpigmented ciliary epithelium (NPE) from a substrate of blood plasma.

• Aqueous humor is distinct from plasma, as it has low protein content and a high concentration of ascorbate.

• Ascorbate has antioxidant properties, and its high concentration in the aqueous protects intraocular structures by blocking ultraviolet (UV) light.

• The blood–aqueous barrier is composed of the tight junctions of the NPE, the iris vasculature, and the inner wall endothelium of the Schlemm canal.

• Disruption of the blood–aqueous barrier allows mixing of blood contents with ocular fluids, producing a plasmoid aqueous, as occurs in anterior uveitis.

Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.