Automonic innervation of Ocular structures

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

2. 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.
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3. Autonomic nervous system (ANS)
Ocular structures innervated by the ANS are
Iris muscles
Ciliary muscle
Smooth muscles of the eyelids
Choroidal and conjunctival blood vessels
Lacrimal gland.
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4. Sympathetic Innervation
▪Sympathetic innervation for ocular structures
originates in segments T-1 through T-3.
▪Ocular structures supplied by the sympathetic
system are the iris dilator, ciliary muscle, smooth
muscle of the lids, lacrimal gland, and choroidal
and conjunctival blood vessels.
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5. Autonomic nervous system (ANS)
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6. Autonomic nervous system (ANS)
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7. 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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8. Autonomic nervous system (ANS)
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10. Autonomic nervous system (ANS)
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11. 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

12. 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.12

13. Autonomic nervous system (ANS)
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Sympathetic
Parasympathetic

14. Neurotransmitters
Adrenergic Cholinergic
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15. DRUGS: AGONISTS AND ANTAGONISTS
Agonist: drug that replicates the action of a neurotransmitter
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Agonist
Direct
acting
Indirect
acting

16. 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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17. Direct-acting agonists
Adrenergic agonist Cholinergic agonist
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18. 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

19. Indirect-acting agonists -Adrenergic
Hydroxyamphetamine Cocaine
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20. Indirect-acting agonist - Cholinergic
Action of Acetylcholinesterase (AChe) Action of Physostigmine
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21. 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, and
tropicamide
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22. Antagonists
Adrenergic antagonist Cholinergic antagonist
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23. Pupillary Reflexes
▪LIGHT REFLEX
▪NEAR REFLEX
▪DARKNESS REFLEX
▪PSYCHOSENSORY REFLEXES
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24. Light Reflex
When light is shone in one eye both the pupils constrict
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25. Pathway of light reflex (Afferent)
The light reflex is mediated by the retinal photoreceptors and carried
out by four neurons
1. 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

26. 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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27. Pathway of light reflex
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28. 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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29. 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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30. 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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31. Pupillary Reflexes
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32. 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.32

33. 33

34. 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

35. 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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36. 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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37. 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.
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38. 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

39. ABNORMALITIES
OF
PUPILLARY REFLEXES
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40. AFFERENT PATHWAY DEFECTS
TOTAL 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

41. Amaurotic pupillary response
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42. 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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43. 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

44. 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

45. 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

46. PUPILLARY LIGHT-NEAR DISSOCIATION
Refers to any situation in which the pupillary near reaction is present
and the light reaction is absent.
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47. PUPILLARY LIGHT-NEAR DISSOCIATION
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48. PUPILLARY LIGHT-NEAR DISSOCIATION
ARGYLL 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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49. SYMPATHETIC PARESIS
HORNER‘S SYNDROME
Paresis of the oculosympathetic innervation due to a lesion in its
pathway
Clinical features-
Ptosis
Upside down ptosis
Miosis
Normal light and near pupillary reflexes
Dilation lag
Facial anhydrosis
Heterochromia irides49

50. THANK
YOU
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