http://upload.wikimedia.org/wikipedia/commons/1/1e/Schematic_diagram_of_the_human_eye_en.svg

The fluid produced by the ciliary process in the eye and occupying the anterior and posterior chambers. It provides nourishment for the lens and cornea and maintains the ocular pressure, and hence the optical integrity of the eyeball. [TFD][VHOG]

FMA says A+P chambers, and MA states A chamber. ZFA states A chamber and tha it is produced primarily by dorsal ciliary epithelial cells.To be investigated across taxa.

uberon

(...) we reach the inescapable conclusion that the last common ancestor of jawless and jawed vertebrates already possessed an eye that was comparable to that of extant lampreys and gnathostomes. Accordingly, a vertebrate camera-like eye must have been present by the time that lampreys and gnathostomes diverged, around 500 Mya (reference 1); Although the eye varies greatly in adaptative details among vertebrates, its basic structure is the same in all. The human eye is representative of the design typical for a tetrapod. (...) A watery aqueous humor fills the spaces in the eye in front of the lens (...) (reference 2).[well established][VHOG]

UBERON:0001796

• ciliary epithelium