autonomic innervation of ocular strucures and pupillary reflexes

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Autonomic Innervation of ocular structures and Pupillary Reflexes Dhanyasree Nair M Optom

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Page 1: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic Innervation of ocular

structures and Pupillary Reflexes

Dhanyasree NairM Optom

Page 2: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic nervous system (ANS)

▪ A type of motor nervous system

▪ Innervates smooth muscles, glands, and the heart and consists of

▪ Sympathetic system - prepares the body to face an emergency

▪ Parasympathetic system - restores the resting state.2

Page 3: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic nervous system (ANS)

Ocular structures innervated by the ANS are Iris musclesCiliary muscle Smooth muscles of the eyelidsChoroidal and conjunctival blood vessels Lacrimal gland.

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Page 4: Autonomic innervation of ocular strucures and Pupillary reflexes

Sympathetic Innervation

▪ Sympathetic innervation for ocular structures originates in segments T-1 through T-3.

▪ Ocular structures supplied by the sympatheticsystem are the iris dilator, ciliary muscle, smoothmuscle of the lids, lacrimal gland, and choroidaland conjunctival blood vessels.

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Page 5: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic nervous system (ANS)

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SYMPATHETIC

Page 6: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic nervous system (ANS)

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SYMPATHETIC

Page 7: Autonomic innervation of ocular strucures and Pupillary reflexes

Parasympathetic Innervation

▪ Parasympathetic innervation of ocular structures originates in the midbrain and pons.

▪ Ocular structures supplied by the parasympathetic system are the iris sphincter, ciliary muscle, lacrimal gland, and blood vessels.

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Page 8: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic nervous system (ANS)

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PARASYMPATHETIC

Page 9: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic nervous system (ANS)

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PARASYMPATHETIC

Page 10: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic nervous system (ANS)

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Page 11: Autonomic innervation of ocular strucures and Pupillary reflexes

Neurotransmitters When an action potential reaches the terminal end of an axon, a

neurotransmitter is released

The neurotransmitter activates either the next fiber in the pathway or the target structure, the effector.

The neurotransmitter binds to effector sites on the muscle and initiates a contraction.

After contraction, it is released from the muscle and is either inactivated or taken back up by the nerve ending, thus preventing muscle spasm

Page 12: Autonomic innervation of ocular strucures and Pupillary reflexes

Neurotransmitters

In the sympathetic pathway the neurotransmitter released by the preganglionic fiber is acetylcholine, and the neurotransmitter released by the postganglionic fiber is norepinephrine.

In the parasympathetic system both preganglionic and postganglionic fibers secrete acetylcholine.

Fibers that release acetylcholine are called cholinergic, and fibers that release norepinephrine are called adrenergic.

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Page 13: Autonomic innervation of ocular strucures and Pupillary reflexes

Autonomic nervous system (ANS)

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Sympathetic

Parasympathetic

Page 14: Autonomic innervation of ocular strucures and Pupillary reflexes

Neurotransmitters

Adrenergic Cholinergic

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Page 15: Autonomic innervation of ocular strucures and Pupillary reflexes

DRUGS: AGONISTS AND ANTAGONISTS

Agonist: drug that replicates the action of a neurotransmitter

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Agonist

Direct acting

Indirect acting

Page 16: Autonomic innervation of ocular strucures and Pupillary reflexes

Direct-acting agonist : structurally similar to the transmitter and duplicates the action of the neurotransmitter by acting on the receptor sites of the effector.

Adrenergic agonists, eg: Epinephrine and phenylephrine

Cholinergic agonists, eg: Pilocarpine

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Page 17: Autonomic innervation of ocular strucures and Pupillary reflexes

Direct-acting agonists

Adrenergic agonist Cholinergic agonist

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Page 18: Autonomic innervation of ocular strucures and Pupillary reflexes

Indirect-acting agonist: Excites the nerve fiber

release of transmitter prevents the reuptake of

neurotransmitter

Adrenergic indirect-acting agonists, eg: Hydroxyamphetamine, Cocaine

Cholinergic indirect-acting agonists, eg: Physostigmine

Page 19: Autonomic innervation of ocular strucures and Pupillary reflexes

Indirect-acting agonists -Adrenergic

Hydroxyamphetamine Cocaine

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Page 20: Autonomic innervation of ocular strucures and Pupillary reflexes

Indirect-acting agonist - Cholinergic

Action of Acetylcholinesterase (AChe) Action of Physostigmine

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Page 21: Autonomic innervation of ocular strucures and Pupillary reflexes

Antagonists: Either block the receptor sites or block the release of the neurotransmitter, thus preventing action of the effector.

Adrenergic antagonists, eg: Dapiprazole

Cholinergic antagonists , eg: Atropine, cyclopentolate, andtropicamide 21

Page 22: Autonomic innervation of ocular strucures and Pupillary reflexes

Antagonists

Adrenergic antagonist Cholinergic antagonist

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Page 23: Autonomic innervation of ocular strucures and Pupillary reflexes

Pupillary Reflexes

▪ LIGHT REFLEX

▪ NEAR REFLEX

▪ DARKNESS REFLEX

▪ PSYCHOSENSORY REFLEXES

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Page 24: Autonomic innervation of ocular strucures and Pupillary reflexes

Light Reflex

When light is shone in one eye both the pupils constrict

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Page 25: Autonomic innervation of ocular strucures and Pupillary reflexes

Pathway of light reflex (Afferent) The light reflex is mediated by the retinal photoreceptors and carried out by four neurons1. First (sensory) connects each retina with both pretectal nuclei in

the midbrain at the level of the superior colliculi.

- Impulses originating from the nasal retina are conducted by fibres which decussate in the chiasm and pass up the opposite optic tract to terminate in the contralateral pretectal nucleus.

- Impulses originating in the temporal retina are conducted by uncrossed fibres (ipsilateral optic tract) which terminate in the ipsilateral pretectal nucleus.25

Page 26: Autonomic innervation of ocular strucures and Pupillary reflexes

Pathway of light reflex (Afferent)

2. Second (internuncial) connects each pretectal nucleus to both Edinger-Westphal nuclei.

-Thus a uniocular light stimulus evokes bilateral and symmetrical pupillary constriction.

-Damage to internuncial neurons is responsible for light-near dissociation in neurosyphilis and pinealomas.

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Page 27: Autonomic innervation of ocular strucures and Pupillary reflexes

Pathway of light reflex

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Page 28: Autonomic innervation of ocular strucures and Pupillary reflexes

Pathway of light reflex (Efferent)

3. Third (pre-ganglionic motor) connects the Edinger-Westphal nucleus to the ciliary ganglion.

-The parasympathetic fibres pass through the oculomotor nerve, enter its inferior division(the nerve supplying the inferior oblique) and reach the ciliary ganglion.

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Page 29: Autonomic innervation of ocular strucures and Pupillary reflexes

Pathway of light reflex (Efferent)

4. Fourth (post-ganglionic motor) leaves the ciliary ganglion and passes in the short ciliary nerves to innervate the sphincter pupillae.

-The ciliary ganglion is located within the muscle cone, just behind the globe.

-Only the parasympathetic fibers synapse in the ciliary ganglion.

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Page 30: Autonomic innervation of ocular strucures and Pupillary reflexes

Near Reflex

Occurs on looking at near objects

Consists of two components – a) Convergence reflex : comprises convergence of visual axes and

associated constriction of the pupils

b) Accommodation reflex : Includes increased accommodation and associated pupillary constriction

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Page 31: Autonomic innervation of ocular strucures and Pupillary reflexes

Pupillary Reflexes

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Page 32: Autonomic innervation of ocular strucures and Pupillary reflexes

Pathway of convergence reflex

Simultaneous contraction of both medial recti

Afferent fibres from the recti muscles travel along the third nerve

Reach the Mesencephalic root of the fifth nerve

Travel to the Edinger-Westphal nucleus via the convergence centre (Perlia’s nucleus)

From Edinger-Westphal nucleus, pathway same as that of light reflex.

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Page 33: Autonomic innervation of ocular strucures and Pupillary reflexes

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Page 34: Autonomic innervation of ocular strucures and Pupillary reflexes

Pathway of accommodation reflex

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Retina

Via Optic nerve, Chaisma Optic Tract

Lateral Geniculate Body

Striate Cortex

Para Striate Cortex

Via Occipitomesencephalic

Tract and Pontine center

EW Nucleus

Via III n. to Sphincter Pupillae

Page 35: Autonomic innervation of ocular strucures and Pupillary reflexes

Darkness Reflex

Light to dark Pupil dilates

Has 2 causes: -Abolition of light reflex relaxation of sphincter pupillae

-Contraction of dilator pupillae

Pathway same as that of light reflex

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Page 36: Autonomic innervation of ocular strucures and Pupillary reflexes

Darkness Reflex

Light to dark Pupil dilates

Has 2 causes: -Abolition of light reflex relaxation of sphincter pupillae

-Contraction of dilator pupillae

Pathway same as that of light reflex

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Page 37: Autonomic innervation of ocular strucures and Pupillary reflexes

Psychosensory reflexes Dilatation of pupil in response to sensory and psychic stimuli.

▪ Absent in a newborn, but appear in the first few days of life and well developed by the age of six months.

▪ Mechanism of psychosensory reflexes is at the cortical level and pupillary dilatation in these results from two components :

-sympathetic discharge to the dilator pupillae

-inhibition of the parasympathetic discharge to the sphincter pupillae.37

Page 38: Autonomic innervation of ocular strucures and Pupillary reflexes

Psychosensory reflexes Lid-closure reflex

May occur in 3 forms – ▪ Following a blink, either voluntary or spontaneous, both pupils

constrict. It is assumed to be a type of darkness reflex.

▪ Constriction occurs if the lid is held open while trying to close it. It is also referred to as lid-closure reflex.

▪ Pupillary dilatation associated with lid-closure on touching the cornea (oculopupillary reflex). It is assumed to be a type of psychosensory reflex.38

Page 39: Autonomic innervation of ocular strucures and Pupillary reflexes

ABNORMALITIES OF

PUPILLARY REFLEXES

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Page 40: Autonomic innervation of ocular strucures and Pupillary reflexes

AFFERENT PATHWAY DEFECTSTOTAL AFFERENT PATHWAY DEFECT (TAPD) OR AMAUROTIC PUPIL

Caused by a complete optic nerve or retinal lesion leading to total blindness on the affected side.

Characterized by the following : Involved eye is completely blind (i.e no light perception)

Absence of direct light reflex on the affected side and absence of consensual light reflex on the normal side.

When the normal eye is stimulated, both pupils react normally.40

Page 41: Autonomic innervation of ocular strucures and Pupillary reflexes

Amaurotic pupillary response

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Page 42: Autonomic innervation of ocular strucures and Pupillary reflexes

RELATIVE AFFERENT PATHWAY DEFECT (RAPD) OR MARCUS GUNN PUPIL

Caused by an incomplete optic nerve lesion or a severe retinal disease.

Paradoxical response of a pupil to light

Tested by ‘swinging flashlight test’

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Page 43: Autonomic innervation of ocular strucures and Pupillary reflexes

EFFERENT PUPILLARY DEFECTS

Characterized by

Absence of both direct and consensual light reflex on the affected side (say right eye)

Presence of both direct and consensual light reflex on the normal side (i.e left eye).

▪ On the affected side, near reflex is also absent and pupils remains fixed and dilated.43

Page 44: Autonomic innervation of ocular strucures and Pupillary reflexes

EFFERENT PUPILLARY DEFECTS

Common causes are Brainstem lesions

Fascicular third nerve lesions

Lesions of the ciliary ganglion

Secondary iris damage

Inadvertent exposure to mydriatic drugs44

Page 45: Autonomic innervation of ocular strucures and Pupillary reflexes

EFFERENT PUPILLARY DEFECTS TONIC PUPIL

Caused by damage to ciliary ganglion or short ciliary nerves

Clinical features- Affected pupil is larger Reaction to light is absent Near reflex is slow Accommodative paresis

Eg: Adie‘s Tonic pupil (due to denervation of postganglionic supply of sphincter pupillae and ciliary muscle of unknown aetiology)45

Page 46: Autonomic innervation of ocular strucures and Pupillary reflexes

PUPILLARY LIGHT-NEAR DISSOCIATIONRefers to any situation in which the pupillary near reaction is present and the light reaction is absent.

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Page 47: Autonomic innervation of ocular strucures and Pupillary reflexes

PUPILLARY LIGHT-NEAR DISSOCIATION

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Page 48: Autonomic innervation of ocular strucures and Pupillary reflexes

PUPILLARY LIGHT-NEAR DISSOCIATIONARGYLL ROBERTSON PUPIL ( ARP )

Most important cause of pupillary light-near dissociation Caused by neurosyphilis in the region of tectum Clinical features-

------Bilateral, miotic pupil with irregular margins and are asymmetrical.

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Page 49: Autonomic innervation of ocular strucures and Pupillary reflexes

SYMPATHETIC PARESISHORNER‘S SYNDROME

Paresis of the oculosympathetic innervation due to a lesion in its pathwayClinical features- Ptosis Upside down ptosis Miosis Normal light and near pupillary reflexes Dilation lag Facial anhydrosis Heterochromia irides49

Page 50: Autonomic innervation of ocular strucures and Pupillary reflexes

THANK YOU

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