Ciliary muscle

Origin: Scleral spur

Insertion: Outer layers of choroid and ciliary processes;

Nerve: Oculomotor nerve (parasympathetics)

Action: Accommodation

Description:
The Ciliary muscle (m. ciliaris; Bowman's muscle) consists of unstriped fibers: it forms a grayish, semitransparent, circular band, about 3 mm. broad, on the outer surface of the fore-part of the choroid. It is thickest in front, and consists mainly of two sets of fibers, meridional and circular. Longitudinal and radial fibers are also described.

The meridional fibers (Brücke's muscle), much the more numerous, arise from the posterior margin of the scleral spur; they run backward, and are attached to the ciliary processes and orbiculus ciliaris. One bundle, according to Waldeyer, is inserted into the sclera (the longitunal fibers).

The circular fibers (Müller's muscle, Rouget's muscle) are internal to the meridional ones, and in a meridional section appear as a triangular zone behind the filtration angle and close to the circumference of the iris. They are well-developed in hypermetropic, but are rudimentary or absent in myopic eyes.

The radial fibers are situated at the middle of the ciliary muscle, crossing from medial to lateral.

The Ciliaris muscle is the chief agent in accommodation, i. e., in adjusting the eye to the vision of near objects. When it contracts it draws forward the ciliary processes, relaxes the suspensory ligament of the lens, and thus allows the lens to become more convex.