The ciliary body is the structure in the eye that releases a clear liquid in the eye. This liquid is called the aqueous humor.
The ciliary body also contains the ciliary muscle. This muscle changes the shape of the lens when your eyes focus on something. This process is called accommodation.
Evans M. Anatomy of the uvea. In: Yanoff M, Duker JS, eds. Ophthalmology. 4th ed. Philadelphia, PA: Elsevier Saunders; 2013:chap 7.1.