Sympathetic innervation to the eye involves a three-neuron chain. Postganglionic parasympathetic pupillary fibers travel along the short ciliary nerves to the ciliary body muscle (93% to 97% of fibers) and to the circumferential iris sphincter (3% to 7% of fibers). The fibers then travel in the superficial layer of the third cranial nerve to the cavernous sinus, follow the cranial nerve’s inferior division through the superior orbital fissure and synapse in the ciliary ganglion, which is posterior to the globe, within the muscle cone. The parasympathetic efferent pupillary pathway begins where the afferent pathway left off: the Edinger-Westphal nucleus. The efferent (motor) pupillary pathway has both parasympathetic and sympathetic nervous system actions. The consensual light reflex occurs because both the optic and tectotegmental tracts carry fibers from both eyes. They then leave the pretectal nucleus and distribute about equally to the two Edinger-Westphal nuclei via the tectotegmental tract. From there, they travel to the midbrain and synapse at the pretectal nucleus, at the level of the superior colliculus. The neural fibers separate from the tract just anterior to the lateral geniculate body. The afferent (sensory) pupillary pathway begins with the retinal photoreceptors, passes through the optic nerve and optic chiasm and travels along the posterior third of the optic tract.
Having an understanding of the neural pathways that control the normal afferent and efferent pupillary responses is foundational, so we will review this before discussing abnormalities of the pupillary response.
The pupils will offer substantial insight into one’s ocular health and the state of the visual pathways before even looking into a patient’s eyes. The keen practitioner can gain helpful information simply by assessing pupillary responses. If you continue to have this issue please contact to Healio
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