Autonomic Innervation of Ocular Structures PDF

Autonomic Innervation of Ocular Structures Karen Gil MD, MHSN Autonomic Nervous System ANS innervates – Smooth muscles – Glands – Heart Consist of – Sympathetic system When stimulated prepares the body for an emergency – Parasympathetic system Maintains and restores the resting state Autonomic Nervo...

Autonomic Innervation of Ocular Structures Karen Gil MD, MHSN Autonomic Nervous System ANS innervates – Smooth muscles – Glands – Heart Consist of – Sympathetic system When stimulated prepares the body for an emergency – Parasympathetic system Maintains and restores the resting state Autonomic Nervous System Ocular structures innervated by the ANS – Supplied by the sympathetic system Iris dilatator Ciliary muscle Smooth muscles of the eyelids Choroidal and conjunctival blood vessels Lacrimal gland – Supplied by the parasympathetic system Iris sphincter Ciliary muscle Lacrimal gland Choroidal and conjunctival Blood vessels Autonomic Pathway Sympathetic innervation for ocular structures originates – Segments T-1 through T-3 Parasympathetic pathway for ocular structures origins – Midbrain and Pons origination Sympathetic Pathway to Ocular Structures Sympathetic fibers are controlled by the hypothalamus stimulus begins here Terminates in the lateral column of the cervical spinal cord The fiber from the preganglionic neuron leaves the spinal cord in one of the first three thoracic nerves Via the ventral root and enters the sympathetic ganglion chain Preganglionic fibers ascend in the sympathetic chain to synapse in the superior cervical ganglion e ↓ before synapse - – Located near the 2nd and 3th cervical vertebrae Sympathetic Pathway to Ocular Structures after synapse Postganglionic fibers leave the ganglion - 1. 2. 3. – 4. 5. Form the carotid plexus around the internal carotid artery Enter the skull though the carotid canal Network of sympathetic fibers for orbital structures leaves the plexus in the cavernous sinus and take multiple pathways to the target structures Some of this sympathetic fibers travel with the ophthalmic division of the trigeminal nerve Once in the orbit follow the nasociliary nerve Then travel with the long ciliary nerves to innervate the iris dilator and the ciliary muscle Mydriasis Relaxation ciliary muscle (inhibitory effect) branches in elong cil.. a Sympathetic Pathway to Ocular Structures Postganglionic Nerve Fibers Other fibers from the carotid plexus follow also the nasociliary nerve and branch to the ciliary ganglion as the sympathetic root These fibers pass though the ganglion without synapsing Enter the globe as the short ciliary nerves to innervate the choroidal blood vessels – vasoconstriction Sympathetic Pathway to Ocular Structures Postganglionic Nerve Fibers Other fibers from the carotid plexus join the oculomotor nerve Travel with it into the orbit to innervate the smooth muscle of the upper eyelid (Muller muscle) – Widening of the palpebral fissure Sympathetic Pathway to Ocular Structures Postganglionic Nerve Fibers Sympathetic stimulation – activates the iris dilator – pupillary dilatation – increasing retinal illumination – Causes vasoconstriction of the choroidal and conjunctival vessels – Causes widening of the palpebral fissure by stimulating the smooth muscle of the eyelid – Causes a small inhibitory effect on the ciliary muscle (relaxation) Distant vision Sympathetic innervation Parasympathetic Pathway to Ocular Structures Preganglionic Neuron Fibers in the parasympathetic pathway to the intrinsic ocular structures is located in the midbrain – In the parasympathetic accessory third-nerve nucleus (EdingerWestphal nucleus) diginationa & will follow oculomotor newe (CN3) E paper Fibers here parasymp > Parasympathetic Pathway to Ocular Structures Preganglionic Nerve Fibers Leave the nucleus Edinger-Westphal nucleus with the motor fivers of the oculomotor nerve Follow the inferior division of the nerve into the orbit Parasympathetic fibers leave the inferior division and enter the ciliary ganglion as the parasympathetic root Parasympathetic Pathway to Ocular Structures Ciliary ganglion parasympathetic fibres synapse – Small, flat structure, 2x1mm – Located within the muscle cone between the lateral rectus muscle and the optic nerve, 1cm anterior to the optic canal – Three roots are located at the posterior edge of the ganglion 1. 2. 3. Parasympathetic root (only fibers that synapse in the ciliary ganglion) Sensory root pass w/o synapsis only signal Sympathetic root , here Parasympathetic Pathway to Ocular Structures Sensory root sensory innervation – Carries sensory fibers from the globe signal ex : ~ if you touch cornea sends Anterior edge of the ciliary ganglion – Short ciliary nerves carry – Sensory fibers – Sympathetic fibers – parasympathetic fibers to brain Parasympathetic Pathway to Ocular Structures Postganglionic paraympathetic fibers Are myelinated enter the globe in the short ciliary nerves Travel to the anterior segment to innervate – Ciliary muscle Zohular fibes gets loose -> Contraction - accommodation – Sphincter muscle Miosis lens expand - accommodation Parasympathetic Pathway to Ocular Structures Parasympathetic stimulation causes – Pupillary constriction decreasing retinal illumination sympathetic - – Contraction of the ciliary muscle Enabling the eye to focus on near objects in accommodation Psympathetic Parasympathetic innervation * Clinical Applications Iris equilibrium – Parasympathetic and sympathetic nerves are in balance in normal awake individuals – Size of the pupil changes constantly and rhythmically because of this balance – Physiologic pupillary unrest is called hippus of opening – During sleep pupils are small small & close Sympathetic system shuts down and parasympathetic system predominates iris parasymp & Symp are fighting "each.. other Autonomic innervation of the Lacrimal Gland ↳ produces tear film-parasympathetic Efferent autonomic pathway – Parasympathetic innervating fibers originate in the Pons in an area designated as the lacrimal nucleus ( within the nucleus for CN VII) – Preganglionic fibers exit the pons with the motor fibers of the facial nerve – Enter the internal auditory canal – Pass through the geniculate ganglion of the facial nerve (without synapsing) only passes the – Leave the ganglion as the greater petrosal nerve (exit the petrous portion of the continues pterygopalatine ganglion temporal bone) phosamena CN7R Autonomic innervation of the Lacrimal Gland Greater petrosal nerve is joined by the deep petrosal nerve (composed of sympathetic postganglionic fibers from the carotid plexus) Greater petrosal and deep petrosal nerves form the vidian nerve change to Autonomic innervation of the Lacrimal Gland Vidian nerve enters the pterygopalatine ganglion or sphenopalatine ganglion(lies in the upper portion of the pterygopalatine fossa) – where parasympathetic fibers synapse It’s a parasympathetic ganglion Autonomic innervation of the Lacrimal Gland Postganglionic autonomic fibers Leave the ganglion join the maxillary branch of the trigeminal nerve Pass into the zygomatic nerve and then form a communicating branch to the lacrimal nerve Autonomic Innervation of the Lacrimal Gland Parasympathetic fibers innervate the lacrimal gland increase secretion – lacrimation Sympathetic fibers innervate blood vessels of the gland (vasoconstriction) – might indirectly cause decreased production of lacrimal gland secretion by restricting blood flow Parasympathetic innervation parasymp synapselele. A Ej Potential test - Sympathetic innervation ?: synapse & superior cervical ganglion y Clinical Application Irritation of any branch of the trigeminal nerve activates a reflex afferent pathway increasing lacrimation Corneal reflex – Corneal touch initiates the three-part reflex Miosis, lacrimation and protective blink – Pain sensation travels to the trigeminal ganglion and then to the pons as the trigeminal nerve – Communication form the trigeminal nucleus to the Edinger-Westphal nucleus causes activation of the sphincter muscle – cause miosis – Communication to the facial nerve nucleus activates the motor pathway to the orbicularis muscle – causing blink – Communication to the lacrimal nucleus and the parasympathetic pathway to the lacrimal gland – increase lacrimation I 60-80 nerves & cornea highly innervated Corneal reflex ~ touch carea Miosis 2) facial nuclei - 2 Orbicularis - 3) lacrimal mulei ~ produce lacimation Crasodilation) - happen & same time close eye Disruption in the Sympathetic Pathway Causes miosis Tone of the dilatator muscle is not present and there is no counteracting pull against the sphincter muscle (parasympathetic)- smaller pupil Anisocoria – difference in pupil size – – – – – Present normal room light More pronounce on dim light Normal eye with the larger pupil Pupil responds briskly to light With slow and incomplete dilatation in the dark Disruption in the Sympathetic Pathway Benign anisocoria lack of sympathetic – – – – 20 % of the population has it Physiologic anisocoria More apparent in dim light Difference between pupils usually less than 1mm – Asymmetric balance between sympathetic and parasympathetic innervation to the iris innervation Disruption in the Sympathetic Pathway Horner’s syndrome 1. Ptosis (loss ofMullers the innervation to the smooth muscle) 2. miosis parasympathetic activated glands 3. facial anhidrosis by – Damage can occur face/side anywhere along the dry sympathetic pathway muscle facial are innevated symp. ~ no sweat on 2 ofthat ~ more wrinkles or Spinal cord Preganglionic path Postganglionic path skin Disruption in the Sympathetic Pathway Horner’s syndrome – Spinal cord lesion have central neuron involvement can cause other problems like vertigo * for Hoener's – Preganglionic fibers leave the dorsal column of the spinal cord, pass into the chest, course over the apex of the lung and loop around the subclavian artery to reach the superior ganglion most common Causes – surgery , thoracic injury, metastatic lung tumors (Pancoast tumor) ↳ most common Disruption in the Sympathetic Pathway Horner’s syndrome – Postganglionic fibers enter the skull through the carotid plexus Damage by fracture of the skull base or an injury to the internal carotid artery Painful Horner’s syndrome is classical on carotid artery dissection Horner’s in combined with 6th nerve paresis (abducens nerve) & – Iack of innervation to lateral rectal muscle indicates cavernous sinus involvement (rule out mass) adduction movement ↑ lateral rectus Disruption in the Sympathetic Pathway Iris heterochromia in Horner’s pupil – Development and maintenance of iris melanocyte pigmentation needs normal sympathetic innervation – Congenital Horner’s syndrome develops abnormal pigmentation – Heterochromia is present – Rarely seen in acquired disease Figure 13.17 Left Horner syndrome due to cervical spinal cord trauma. A. In room light, the left pupil is miotic, and there is left upper lid ptosis. The left iris is lighter in color than the right (acquired heterochromia) Accommodation – Convergence Reaction Its not a reflex, is a silkiness of actions – Convergence – Accommodation – Miosis Near object along the midline – Medial rectus muscle contract to move the image to the fovea – Ciliary muscle contract to keep the near object in focus – Sphincter muscle constricts to decrease the size of the pupil Accommodation – Convergence Reaction Afferent pathway for this reaction follows the visual pathway to the striate cortex Striate cortex sent the information to the frontal eye fields which communicate with the oculomotor nucleus and the Edinger-Westphal nucleus though a pathway through the internal capsule Accommodation – Convergence Reaction Efferent pathway – Via the oculomotor nerve innervates the medial rectus muscle – Parasympathetic pathway innervates the ciliary muscle an iris sphincter miosis and accommodation Pupillary Light Pathway Shining a bright light into a normal eye will initiate pupillary constriction Afferent fibers that carry this information are called pupillary fibers Pupillary light pathway parallels the visual pathway as far as the posterior optic tract with the nasal fibers crossing in the chiasm Pupillary Light Pathway Pupillary fibers exit the posterior third of the optic tract and travel within the brachium of the superior colliculus to an area of the midbrain known as the pretectal nucleus (located at the superior colliculus) – Fibers synapse and leave to the two Edinger-Westphal nuclei – Fibers that cross to the opposite Edinger-Westphal nucleus travel in the posterior commissure Consensual pupillary response Pupillary Light Pathway Third nerve leaves the midbrain Pupillomotor fibers lie in the superior portion, but as they leave the cavernous sinus and enter the orbit move into an inferior portion and travel in the inferior division of the oculomotor nerve Pupillary Light Pathway While parasympathetic system is activated Inhibition of dilator muscle occurs – Miosis When the light stimuli is removed – Edinger-Westphal neurons stop firing – Preganglionic sympathetic fibers are no longer inhibited – firing rate increase- dilator muscle increases Pupillary Light Response Assessment of the pupillary pathway – Direct and consensual response are tested Bright light is direct into the eye both responses occur (constriction of the ipsilateral and contralateral iris) Consensual response occur because of the two crossings of the fibers in the pathway Disruption in the Afferent Pupillary Pathway Disruption to the afferent pupillary pathway affect both direct and consensual responses Example – disruption right afferent pathway – Light directed to the right eye will cause a poor response in both eyes – Response will be normal if the light is directed to the left eye Damage to the complete afferent pathway of one eye – No direct and consensual response when light is directed into the affected eye Disruption in the Afferent Pupillary Pathway More often only some fibers are damaged – Abnormal pupillary responses might be recognized only when compared with the normal pupillary responses – Term as relative afferent pupillary defect (RAPD) Disruption can occur anywhere – Retina, optic nerve, optic chiasm, optic tract or midbrain Swinging-flashlight test used to determine presence of a RAPD Swinging-Flashlight Test Patient is asked to fixate on a distant object Practitioner swings a light form eye to eye Several times, rhythmically for an equal time each pupil (2-3 seconds) Normal response- little or not change in pupil size will be noted, the eye will not recover from the consensual response before it is subjected to the direct light beam Symmetric response characterized by equal pupillary constriction in both eyes Swinging-Flashlight Test Abnormal response – Larger pupils when the light is directed into the affected eye than when the light is directed into the normal eye Most common site of damage in a RAPD is the optic nerve – optic neuritis 90 % Afferent pupillary defect in cataract – Dense cataract were the light not penetrate to stimulate the retina Disruption within the Central Nervous System Lesion on the midbrain – Injury to the dorsal tegmentum that interrupts the fibers from the pretectal nucleus to the parasympathetic third nerve nucleus – One side affected, affecting all fibers into the Edinger-Westphal nucleus causes Argyll Robertson pupil – Pupil that shows a poor direct and consensual response but does constrict with near response ‘light near dissociation’ (fibers pass more ventral) Disruption within the Central Nervous System Argyll Robertson syndrome present – Miosis in darkness with the affected pupil smaller than a normal individual – 80 to 90 % is bilateral, can be affected unequally – Complete Argyll Robertson syndrome causes Diabetic neuropathy Alcoholic neuropathy Neurosyphilis Argyll Robertson pupils in tabes dorsalis (absent deep tendon reflexes, loss of vibratory sense and proprioception in the lower extremities, and Charcot joints). The pupils are small (A) and poorly reactive to light (B) but constrict during near viewing (C). Disruption in the Efferent Pathway Eye shows poor direct and consensual pupillary responses and a poor near response Pupil appears large on clinical presentation Other ocular structures can be involved if oculomotor nucleus is involved (superior, medial or inferior rectus, inferior oblique or elevator muscle) Damage to the ciliary ganglion or the short ciliary nerves results in a tonic pupil – – – Poor pupillary light response and loss of accommodation Near response retained but is delayed and slow Pupils re-dilates sluggishly Disruption in the Efferent Pathway Adie’s Tonic Pupil – No cause apparent to a tonic pupil – Characteristic patient Woman 20 – 40 y/o 90 % with diminish tendon reflexes Probably associated with autoimmune diseases – Probable degenerative processes occurring in the ciliary ganglion and in the dorsal column of the spinal cord – Cause unknown Disruption in the Efferent Pathway Adie’s Tonic Pupil – Examined with biomicroscope – Segmental constriction affecting only a section of the iris may be evident – Eventually with the years become smaller and does not dilate in dark – larger pupil in light and smaller in dark – Pilocarpine (0.625 or 0.125 %) solution still cause significant miosis – Differential diagnoses for fixed dilated pupil Drug induced mydriasis Chemical induced Drops OTC Figure 13.13 Idiopathic right tonic pupil. The right pupil is midposition and larger than the left ( A ), poorly reactive to light, but reactive during near viewing (the examiner's thumb) ( B ). The patient complained of blurry vision in the right eye while attempting to read, consistent with accommodation paresis. After instillation of 0.125% pilocarpine eye drops at 0 and 5 minutes into both conjunctivae, 30 minutes later the right pupil constricted while the left did not (( C ) compared with ( A )), indicating denervation hypersensitivity on the right.