The ciliary body is made up of two components – the ciliary processes and the ciliary muscle. The ciliary muscle and the ciliary processes are part of the choroid and uveal system, a muscular tissue filled with blood vessels that lines the inner part of the eye starting at the back of the retina moving anteriorly towards the cornea to include the ciliary muscle and the iris. The uveal system is highlighted in pink in the picture below. (Note: there is no depiction of Mary Ann Croft’s vitreous zonule in the picture below, which should attach to the bottom of the ciliary body and then reattach to the choroid 4-5 mm posterior to the ciliary body, since Mary Ann had not yet discovered the vitreous zonule when this picture was created).
The ciliary processes are composed of loose soft tissue that is layered in folds somewhat like petals on a flower. The ciliary processes are attached to the ciliary muscle and move in lock-sync with the ciliary muscle during accommodation. The ciliary processes produce aqueous which is designed to keep the eye round by applying pressure to its exterior surfaces, especially in the anterior chamber, and also to provide nourishment for the cornea. As mentioned, the aqueous drains through the trabecular meshwork at the juncture of the iris and the cornea in the anterior chamber, and eventually into channels outside of the eye. All of the anterior, equatorial, and posterior zonules attach to or within the ciliary processes. The ciliary muscle is technically a “smooth” muscle (an involuntary non-striated muscle such as found in the heart, the intestines or the urinary bladder), that operates independently of conscious neurological stimulus. However, in many respects the ciliary muscle acts like a “skeletal” striated muscle in that it can be controlled voluntarily whenever a person wants to accommodate.
Almost all scientists and ophthalmologists believe that the motion of the ciliary muscle and the attachment points of the zonules on or in the ciliary processes are the primary drivers of accommodation. However, how the ciliary muscle actually executes the accommodative process is still a subject of significant debate.