The Aqueous Humor is the fluid that exists between the cornea and the lens of the eye. It provides the pressure necessary to inflate the cornea, and the nutrients necessary for both the cornea and lens health. The flow of Aqueous humor is regulated by the ciliary muscle, a relaxed ciliary muscle opens up Schlemm's canal for drainage, while the fluid is produced by the ciliary body that contains the ciliary muscle and is influenced by the same nerves that affect the ciliary muscle. Increased Aqueous Humor pressure is a risk factor for glaucoma. The cornea is partially supported by the pressure of the aqueous humor, and may have it's shape influenced by that pressure.
EM tends to focus on the axial length component of refractive state but the lens and the cornea, both influenced by aqueous humor are also major contributors to refractive state, and could be important factors in myopia recovery.