2020–2021 BCSC Basic and Clinical Science Course™
2 Fundamentals and Principles of Ophthalmology
Part I: Anatomy
Chapter 1: Orbit and Ocular Adnexa
The ciliary ganglion is located approximately 1 cm in front of the annulus of Zinn, on the lateral side of the ophthalmic artery, between the optic nerve and the lateral rectus muscle (Fig 1-10). It receives 3 roots:
A long (10–12-mm) sensory root arises from the nasociliary branch of CN V1 and contains sensory fibers from the cornea, the iris, and the ciliary body.
A short motor root arises from the inferior division of CN III. It carries preganglionic parasympathetic fibers from the Edinger-Westphal nucleus. The fibers of the motor root synapse in the ganglion, and the postganglionic fibers carry parasympathetic axons to supply the iris sphincter.
A sympathetic root carries postganglionic fibers originating from the superior cervical ganglion, from which they course superiorly with the internal carotid artery. In the cavernous sinus, the sympathetic fibers leave the carotid artery to temporarily join the abducens nerve before entering the orbit either with the nasociliary branch of CN V1 or as an individual root. The sympathetic root enters the orbit through the superior orbital fissure within the tendinous ring, passes through the ciliary ganglion without synapse, and innervates blood vessels of the eye, as well as the dilator muscle of the pupil. Fibers destined for the Müller muscle travel along the frontal and lacrimal branches of CN V1.
Branches of the Ciliary Ganglion
Only the parasympathetic fibers synapse in the ciliary ganglion. The sympathetic fibers are postganglionic from the superior cervical ganglion and pass through it without synapsing. Sensory fibers from cell bodies in the trigeminal ganglion carry sensation from the eye, orbit, and face. Together, the nonsynapsing sympathetic fibers; the sensory fibers; and the myelinated, fast-conducting postganglionic parasympathetic fibers form the short ciliary nerves (see also Chapter 3, Fig 3-18).
Figure 1-10 Ciliary ganglion. Schematic of the lateral orbit with ciliary ganglion. Note the 3 roots: (1) sensory root, which carries sensation from the globe to the trigeminal ganglion via the nasociliary nerve; (2) sympathetic root carrying postganglionic sympathetic fibers from the superior cervical ganglion and carotid plexus; (3) motor root carrying preganglionic parasympathetic fibers from the inferior division of the oculomotor nerve.
(Modified with permission from Levin LA, Nilsson SFE, Ver Hoeve J, Wu SM. Adler’s Physiology of the Eye. 11th ed. Philadelphia: Elsevier/Saunders; 2011:364.)
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.