A ring of tissue that contains muscles and "fibers" that adjust lens thickness to focus light on the retina, so that we can see. In addition, it produces fluid to provide nutrients and take away waste from the lens and cornea, thus helping to control eye pressure.
The ciliary body, located in a "ring" around the iris, is responsible for controlling the shape of the lens, via muscle connections to "fibers" attached to the lens, a process that controls how light focuses on the retina. In addition, it creates fluid (called aqueous humor) that provides nutrients to and takes waste away from the lens and the cornea. Glaucoma drugs target the ciliary body to lower aqueous humor production and cause a drop in the intraocular pressure.