Which structure is responsible for producing aqueous humor?

The ciliary body is responsible for producing aqueous humor, which is a clear fluid that fills the anterior chamber of the eye. This structure is located behind the iris and is composed of both ciliary muscle and ciliary processes. The ciliary processes, in particular, secrete the aqueous humor into the anterior chamber, playing a crucial role in maintaining intraocular pressure and providing nutrients to the avascular structures of the eye, such as the lens and cornea.

In contrast, the iris is primarily responsible for regulating the amount of light entering the eye by controlling the size of the pupil. Although the cornea is essential for focusing light and is involved in the eye's optical properties, it does not produce aqueous humor. Similarly, the lens focuses light onto the retina but also does not have a role in the production of this fluid. Therefore, the ciliary body distinctly stands out as the correct answer for its role in aqueous humor production.