The lens is a flexible structure about the size and shape of an aspirin tablet. Like the cornea, the lens is transparent because it contains no blood vessels and is relatively dehydrated. The muscles of the ciliary body make constant adjustments in the shape of the lens. The adjustments produce a sharp visual image at all times as the eye shifts focus between nearby and distant objects. Both the cornea and lens are kept nourished and lubricated by a clear, watery fluid produced continuously by the ciliary body called aqueous humor.
Aqueous humor fills the area between the lens and cornea.
Fluid that has already nourished both these parts of the eye flows into a drainage system at a spongy, circular groove where the cornea and the sclera meet. It then travels through the veins of the eyeball into the veins of the neck.