A comprehensive list of abbreviations used in this article can be found in table 1.Įdinger-Westphal centrally projecting cells Unless otherwise stated, primary references reflect studies conducted in the primate model. Our discussion of these topics is concentrated on primates, including humans, but includes data from other species where it suggests alternative connections that have yet to be investigated in primates, or where primate data is unavailable. ![]() The information presented below focuses not only on the autonomic innervation of the eye, but also the central autonomic pathways controlling pupillary reflexes, accommodation, ocular blood flow, and intraocular pressure. Abbreviations: ACh – Acetylcholine ATP – Adenosine triphosphate CG – Ciliary ganglion EWpg – Edinger-Westphal nucleus, preganglionic IML – Intermediolateral nucleus (cell column) NA – Noradrenaline nNOS – neuronal nitric oxide synthase NPY – Neuropeptide Y PPG – Pterygopalatine ganglion SCG – Superior cervical ganglion SSN – Superior salivatory nucleus VIP – Vasoactive intestinal peptide. Neurotransmitters and neuropeptides that are generally present in postganglionic neurons are identified. For example, both iris and ciliary muscle contraction can influence aqueous humor outflow, while alterations in choroidal blood flow will cause changes in IOP.Ī schematic diagram showing the parasympathetic and sympathetic innervation of the eye. However, as discussed below, these functional subdivisions are somewhat arbitrary since they are often interrelated and do not operate in isolation. Autonomic regulation of ciliary body blood vessels and the ciliary epithelium are important determinants of aqueous humor formation, while regulation of the trabecular meshwork and episcleral blood vessels are important determinants of aqueous humor outflow – these structures are innervated by postganglionic fibers from the pterygopalatine (parasympathetic) and superior cervical (sympathetic) ganglia ( Figure 1). In birds, the ciliary ganglion also contributes to the parasympathetic innervation of the choroid, and there may be a small contribution from this ganglion in mammals 3) intra-ocular pressure (IOP), which is regulated primarily through changes in aqueous humor formation and outflow. In mammals, these vascular beds are innervated by postganglionic fibers from the pterygopalatine (parasympathetic) and superior cervical (sympathetic) ganglia. These include: 1) pupil diameter and ocular accommodation, which are controlled by the intrinsic muscles of the eye located in the iris and ciliary body respectively – these structures are innervated by postganglionic fibers from the ciliary (parasympathetic) and superior cervical (sympathetic) ganglia 2) Ocular blood flow, which is controlled via innervation of the vasculature within the optic nerve, the retina, choroid, ciliary body, and iris. ![]() The ocular projections of the autonomic nervous system influence numerous functions of the eye. In addition to these classical autonomic pathways, trigeminal sensory fibers exert local, intrinsic influences on many of these regions of the eye, as well as on some neurons within the ciliary and pterygopalatine ganglia. These tissues are all innervated by fibers from the pterygopalatine and superior cervical ganglia. Autonomic regulation of ciliary body blood vessels and the ciliary epithelium is an important determinant of aqueous humor formation autonomic regulation of the trabecular meshwork and episcleral blood vessels is an important determinant of aqueous humor outflow. Intraocular pressure is regulated primarily through the balance of aqueous humor formation and outflow. In mammals, this vasculature is innervated by vasodilatory fibers from the pterygopalatine ganglion, and by vasoconstrictive fibers from the superior cervical ganglion. ![]() Ocular blood flow is controlled both via direct autonomic influences on the vasculature of the optic nerve, choroid, ciliary body, and iris, as well as via indirect influences on retinal blood flow. Superior cervical ganglion neurons project to the dilator pupillae muscle of the iris to control pupil dilation. Ciliary ganglion neurons project to the ciliary body and the sphincter pupillae muscle of the iris to control ocular accommodation and pupil constriction, respectively. It does this by way of parasympathetic innervation from postganglionic fibers that originate from neurons in the ciliary and pterygopalatine ganglia, and by way of sympathetic innervation from postganglionic fibers that originate from neurons in the superior cervical ganglion. The autonomic nervous system influences numerous ocular functions.
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