Structure and Roots of the Ciliary Ganglion - Ciliary ganglion is located just behind the eye in the posterior orbit and is 1-2 mm in diameter. - Contains approximately 2,500 neurons in humans. - Contains postganglionic parasympathetic neurons. - Supplies the pupillary sphincter muscle and the ciliary muscle. - Three types of axons enter the ciliary ganglion: sensory root, sympathetic root, and parasympathetic root. - Sensory root branches from the nasociliary nerve and supplies the cornea, ciliary body, and iris. - Sympathetic root originates from the internal carotid plexus and provides sympathetic supply to the blood vessels of the eye. - Parasympathetic root branches from the inferior division of the oculomotor nerve and carries preganglionic parasympathetic axons from the Edinger-Westphal nucleus. - Axons synapse onto postganglionic parasympathetic neurons within the ganglion. - Short ciliary nerves exit from the anterior surface of the ciliary ganglion and contain sensory, postganglionic sympathetic, and postganglionic parasympathetic axons to the eye.

Clinical Significance and Diseases - Diseases of the ciliary ganglion can produce a tonic pupil. - Tonic pupil does not react to light and has an abnormally slow and prolonged response to attempted near vision. - Adie syndrome is a common disease that affects the ciliary ganglion and causes tonic pupil plus absent deep tendon reflexes. - Other diseases and conditions can denervate the ciliary ganglion and produce a tonic pupil. - Trauma to the orbit can damage the short ciliary nerves.

Physiology and Tonic Pupil - Tonic pupil explained by Irene Loewenfeld's theory. - Ciliary ganglion contains more nerve fibers directed to the ciliary muscle than the pupillary sphincter muscle. - Pathological destruction of nerve cells in the ciliary ganglion leads to aberrant nerve regeneration. - Tonic constriction of the pupil with attempted near vision due to abnormal innervation of the ciliary muscle. - Denervation supersensitivity causes the iris to become supersensitive to acetylcholine and constrict with weak cholinergic substances.

Light-near Dissociation - Pupil does not react to light, but reacts to accommodation. - Light-near dissociation occurs in some neurological disorders. - Adie syndrome causes light-near dissociation and tonically dilated pupil. - Brainstem damage can also cause light-near dissociation. - Argyll Robertson pupil and Parinaud syndrome are brainstem causes of light-near dissociation.

Additional Information - Plan of oculomotor nerve. - Connections of the right sympathetic chain with thoracic, abdominal, and pelvic plexuses. - Diagram of efferent sympathetic nervous system. - Irene Loewenfeld is credited as the first physiologist to make the distinction of light-near dissociation.

References and External Links: - Perez and Keyser (1986) conducted cell body counts in human ciliary ganglia. - Kawasaki (1999) discussed physiology, assessment, and disorders of the pupil. - Thompson and Kardon (2006) wrote about Irene E. Loewenfeld, a physiologist of the pupil. - Thompson (1977) made new observations on Adie syndrome. - Various references with relevant information on the topic. - Anatomy figure: 29:03-04 at Human Anatomy Online, SUNY Downstate Medical Center - A deeper dissection of the right orbit from a superior approach.