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DR R PATEL
Pupillary Pathway
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The iris (the coloured part of the eye) is a musclewhich controls the size of the pupil.
The pupil changes size according to the amount oflight available. When it is dark the pupil opens up wide(dilates) to let as much light as possible into the eye so
you can see more clearly.A nother amazing fact
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In bright light In dim light
•Radial muscles of the
iris relax.
•Circular muscles of the
iris contract.
•Less light enters the
eye through thecontracted pupil.
•Radial muscles of the
iris contract.
•Circular muscles of the
iris relax.
•More light enters the
eye through the dilatedpupil.
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Pupil
• Circular hole in the middle of the iris.
• Acts like the shutter of a camera:
– In darkness the iris dilator muscle causes the pupil
to ―dilate‖ and allowing more light to reach the retina. – In brightness, the iris sphincter muscle (which
encircles the pupil) constricts, causing the pupil to―constrict‖ and allowing less light to reach the retina.
• Constriction also occurs during accommodation- the ―near reflex.‖
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Dr. Azza Zaki
Intra-Ocular Muscles
The muscles of the iris:
1- sphincter pupillae: circular in shape and are arranged aroundthe margin of the pupil.
Action: constrict the pupil in the presence of bright light.&during accomodation.
Nerve supply : parasympathetic
fibers from the oculomotor nerve(short ciliary branches of ciliary
ganglion.
2- dilator pupillae:
Radial fibers
Action:
Dilate the pupil in the presence
of light of low intensity & excessive
sympathetic stimuli as in fear.
Nerve supply : sympathetic fibers along long ciliary nerve.
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Muscles of iris Dilator muscles Origin: iris root Insertion :2 mm from pupillary
margin Orientation :radial
NS : – myoepithelial cellsinnervated by sympathetics fromsuperior cervical ganglia (V1 via thelong ciliary nerve)
Iris sphincter Orientation :circumferential around
the pupil Lies withen 2-3 mm of pupil margin NS : – smooth muscle innervated
by postganglionic parasympathetic
fibers from the ciliary ganglia (CN 3via the short ciliary nerves)
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Muscles of iris
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Pupil
Normal size : 2-4mm
In dark adaption : 4.5-7 mm
In light adaption : 2.5-6 mm
Miosis : =/<3mm
Mydriasis : =/> 6mm
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The pupil allows light to enter the posterior
segment of the eye.
The iris constricts or dilates to adjust size of the pupil.
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Pupil Dilation and Constriction, Anterior View
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Light reflexFirst (sensory) connects each retina with both pre-tectal nuclei in the midbrain at the level ofthe 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 pre-tectalnucleus.
Impulses originating in the temporal retina are conducted by uncrossed fibres (ipsilateraloptic tract) which terminate in the ipsilateral pre-tectal nucleus.
Second (internuncial) connects each pre-tectal nucleus to both Edinger-Westphalnuclei.
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.
Third (pre-ganglionic motor) connects the Edinger-Westphal nucleus to the ciliaryganglion.
The parasympathetic fibres pass through the oculomotor nerve, enter its inferior divisionand reach the ciliary ganglion via the nerve to the inferior oblique muscle
.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. It should be noted that, although the ciliary ganglion serves as a conduit for other nerve
fibres, only the parasympathetic fibres synapse there.
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Points of Interest
Within the second order neuron there
are 30 near response fibers for every lightresponse fiber. This allows for light - neardissociation.
The third order neuron runs withcranial nerve III from the brain stem to theciliary ganglion. Superficially located priorto the cavernous sinus.
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4-neuron pathway:
i.Retinal ganglion cells optic nerve optic chiasm optic tract synapse inpretectalnuclei of dorsal
midbrain ii.Pretectalnuclei Edinger-Westphalnuclei(bilateral innervation!)
iii.Parasympathetic fibrestravel along CN3 -
Ipsilateral ciliaryganglionwithin orbit iv.Postganglionic
parasympathetic fibres- pupillary sphincter muscles
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Visual pathway
Optic nerve
Optic chiasma
Optic radiation
Lateral geniculate body
Visual area
Optic tract
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Pretectal area
Accessory oculomotor nuclei
Occculomotor n.
Ciliary ganglia
Sphincter pupilCiliary muscle
Pupillary reflexes
A f h
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Anatomy of theparasympathetic outflow
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Parasympathetic pathway
• First Order – Retina to Pretectal Nucleus inB/S
(at level of Superior colliculus)
• Second Order – Pretectal nucleus to E/Wnucleus
(bilateral innervation!)
• Third Order – E/W nucleus to CiliaryGanglion
• Fourth Order – Ciliary Ganglion to Sphincter
pupillae (via short ciliary
nerves)
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Sympathetic Pathway
First Order – PosteriorHypothalamus to
Ciliospinalcentre of Budge (C8-T2)
(Uncrossed
in Brainstem) Second Order –
Ciliospinal centre of Budgeto
SuperiorCervical Ganaglion
Third Order – SuperiorCervical Ganglion to
dilatorpupillae muscle. (Close to
ICA and
joins V1 intracranially)
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Sympathetic Pathway The sympathetic supply involves three
neurons
First (central) starts in the posteriorhypothalamus and descends, uncrossed,down the brainstem to terminate in theciliospinal centre of Budge, in theintermedio-lateral horn of the spinal cord,
located between C8 and T2.
Second (pre-ganglionic) passes from theciliospinal centre to the superior cervicalganglion in the neck. During its long course, itis closely related to the apical pleura where itmay be damaged by bronchogenic carcinoma(Pancoast tumour) or during surgery on the
neck.
Third (post-ganglionic) ascends along theinternal carotid artery to enter the cavernoussinus where it joins the ophthalmic division ofthe trigeminal nerve. The sympathetic fibresreach the ciliary body and the dilator pupillaemuscle via the nasociliary nerve and the
long ciliary nerves.
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Points of Interest
Second order neuron runs along the surface ofthe lung, can be affected
by a Pancoast tumor
Third order neuronruns with the carotidartery then with theophthalmic division ofcranial nerve V
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Near reflex
• Near reflex occurs on looking at a near
object.
• It consists of two components:
• (a) convergence reflex, i.e., contractionof pupil on convergence; &
• (b) accommodation reflex, i.e.,contraction of pupil associated withaccommodation.
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Pathway of convergence reflex
Its afferent pathway is still notelucidated.
Afferent path from themedial recti travel centrally via the CN3 to the mesencephalicnucleus of the fifth nerve, to a presumptive convergencecentre in the tectal or pretectal region.
From this the impulse is relayed tothe Edinger-Westphal nucleusand the subsequent efferentpathway of near reflex is along the3rd nerve.
Efferent path fibres relayin the accessory ganglion beforereaching the sphincter pupillae.
P th f d ti
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Pathway of accommodation
reflex • Afferent path impulses extend from the
retina the optic nerve, chiasma, optictract, lateral geniculate body, opticradiations, striate cortex (17) . parastriatecortex (19)
• From the parastriate cortex pontine centre occipito-mesencephalic tract Edinger-Westphal nucleus (bilateral innervation!)
• Efferent path Edinger-Westphalnucleus the efferent impulses travel along the 3rd nerve and reach the
• sphincter pupillae (miosis)• ciliary muscle(accomodation) after relaying
in the accessory and ciliary ganglions
• medial rectus (convergence of the eyes).
• Change in the lens (thickening) that occursduring accommodation. The pull of the ciliarymuscle relaxes the zonular fibers and allows
the lens to become more convex
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The occulomotor nerve (cranial nerve III) controls some muscles on the outside ofthe eye (extrinsic) and some muscles on the inside of the eye (intrinsic).
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Optic nerve
Optic chiasma
Optic tract
Lateral geniculatebody
Optic radiation
Visual area
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The iris reflex
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• In bright light, light enters eye, absorbed byphotoreceptor cells in retina
• Nerve impulses in neurones in optic nerve• Impulses visual cortex vision• Some impulses midbrain coordinating centre• impulses along parasympathetic nerve (oculomotor
nerve) to circular muscles contraction• No impulses along sympathetic nerve relaxation of
radial muscles• stretch back to full length by antagonistic
contraction of circular muscles.
Function: • To reduce the amount of light entering the eye in
bright light to prevent damage to the retina and toavoid producing an over-exposed image.
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• In dim light nerve impulses along the sympatheticnerve contraction of radial muscles to widen iris
• No impulses along parasympathetic nerve relaxation of
circular muscles which are stretched back to their fulllength by the action of the antagonistic radial muscles
• Function• To let more light in to provide sufficient stimulation of
the retina to produce a clear image.
• Red eye reduction
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REFLEXES: Accomodation
• Pupils constrict when adjusting foraccommodation – vision for near objects
• Involves: – Pupillary miosis (sphincter pupillae) – Convergence (medial rectus muscle) – Accomodation (ciliary muscle)
• Near: Pupil is constricted, lens is fat
Far: Pupil is dilated, lens is thin• All 3 have a common efferent pathway – III(oculomotor)
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ACCOMODATION VS. LIGHT
• Accommodation pathway: visual cortex toCNIII nucleus
• Absent light, Intact accommodation
– Midbrain lesion (i.e., Argyll Robertson,syphilis)
– Cilliary ganglion lesion (i.e. Adie’s pupil)
• Failure of accommodation alone – Midbrain lesion (occasional)
– Cortical blindness
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REFLEXES: Corneal Reflex
• Blinking – elicited by sensory stimulationof cornea
• A direct and consensual response
• Sensory: CNV1 (ophthalmic division oftrigeminal)
• Motor: CN VII (facial)
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PUPIL
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Points to be noted in pupil
1. Number-normally there is one pupil.More than one pupil is called polycoria.
2. Location- normally almost central,
slightly nasal. Eccentric pupil is calledcorrectopia.
3. Size of pupils
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Pupillary size
• Size- 3-4 mm normal, depending on illumination• Causes of abnormally small pupil - miosis
Local miotic Drugs (parasympathomimetic)Systemic morphine
Iridocyclitis- narrow, irregular, non-reacting pupilMorphineHorner’s syndrome Head injury (pontine hemorrhage)
Senile miotic pupilEffect of strong lightDuring sleep
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Dilated pupil
Causes of abnormally dilated pupil - mydriasis Sympathomimetic drugs- adrenaline, phenilephrine
Parasympatholytic drugs- atropine, homatropine, cyclopentolate,tropicamide
Acute congestive glaucoma (vertically oval, immobile pupil)
Absolute glaucoma
Optic atrophy
Retinal detachment
Internal ophthalmoplegia
3rd nerve paralysis
Belladonna poisoning
Wh di l It li
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Why medieval Italian womenused Belladonna
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Pupillary size assessment
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Testing Pupillary Reactions
• Pupillary Reflexes : Light reflex- direct / Consensual
• Near reflex- a) convergence reflex b)
accommodation reflex• Testing light near dissociation
• Testing RAPD: 1.Swinging flash light test
2.Kestenbaums number 3 Pulfrichphenomenon 4. testing edge-light pupil cycletime 5.pharmacology testing
Test Pupillary Reactions to Light
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Dim the room lights as necessary.
Ask the patient to look into the distance.
Shine a bright light obliquely into each pupil in turn.
Look for both the direct (same eye) and consensual (othereye) reactions.
Record pupil size in mm and any asymmetry or irregularity.
If abnormal, proceed with the test for accommodation.
Test Pupillary Reactions to Light
Test Pupillary Reactions to
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1:Hold your finger about 10cm from thepatient's nose.
2 :Ask them to alternate looking into thedistance and at your finger.
3 :Observe the pupillary response in eacheye.
Test Pupillary Reactions toAccommodation
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Swinging flash light test
Patient is made to sit in a room with diffusebackground illumination
Direct torch into one pupil and noteconstriction
Quickly move to contra-lateral pupil note thereaction Repeat this to and fro swinging, rhythmically,
several times while observing response Normally both pupils constrict equally In presence of rapid afferent pupillary defect
(RAPD) or Marcus Gunn pupil, the affectedpupil shows a reduced amplitude ofconstriction and accelerated dilatation
(recovery) as compared to contralateral eye
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RAPD or Marcus Gunn pupil
Examination of the pupils
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Examination of the pupilsPERRL
P Pupils
E Equal
R Round
RL Reactive to Light
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Horner’s Syndrome
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Horner s SyndromePERRL
(Ptosis, Miosis and Anhydrosis)
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• Sympathetic
Pathways to
the eye
n socor a
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n socor a(unequal pupils)
Horner’s Syndrome
Third Cranial Nerve Palsy
Damage to the Iris and Pupil
Eye Trauma
Surgical Trauma
PERRL
Irregular pupils
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Irregular pupils
Argyl-Robertson
Possible other manifestation of CNS disease
BUT most commonly due to IntraocularCongenital AnomalyInflammation
TraumaSurgery
PERRL
Irregular Pupil after IOL
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Irregular Pupil after IOLimplantation
P ill Li h R fl
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Pupillary Light Reflex
PERRL
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PERRL
Pupil Light ReflexesDirect Response – constriction of pupilwhen light shined into that eye
Consensual Response – constriction ofpupil of non-stimulated eye
Consensual Response of
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Consensual Response ofPupils to Light
In normal subject Both Pupils willconstrict equally to light shined in one eye
Basis for Swinging Flashlight test
Marcus Gunn (Sign of possible opticnerve disease)
Poor Pupil Reaction to Light
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Poor Pupil Reaction to Light
Diabetics
Neurologic DiseaseOptic Nerve Disease
Sign of possible serious ocular problemAcute Angle ClosureUveitis
Damage to Pupil fromSurgeryTrauma PERRL
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Afferent Pupillary Defect
Swinging light test
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Swinging light testAfferent Papillary Defect
R l ti Aff t P il D f t
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Relative Afferent Pupil Defect
V.A. 20/20 20/20
Left RAPD
P ill APD
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Pupillary exam: APD
sft.jpg
AFFERENT PUPILLARY
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AFFERENT PUPILLARYDEFECT
• Total loss of the AFFERENT reflexpathway
– Blind eye, i.e. severe retinal damage or optic
nerve pathology
• For a LEFT APD
– Light into left eye: no direct light reflex (L)
– Light into left eye: no consensual reflex (R) – Light into right eye: normal direct and
consensual reflex
RELATIVE AFFERENT
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RELATIVE AFFERENTPUPILLARY DEFECT
• Incomplete damage to AFFERENTpathway
– Partial retina or optic nerve damage
• For LEFT RAPD – Light into left eye: left and right pupil constrict
– Light into right eye: both pupils constrict
further – Back to left eye: both pupils dilate, but not
completely
– Light away: both pupils dilate completely
GRADING OF RAPD
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GRADING OF RAPD
1st animation
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13/04/2012 77
Watch
I will describe what is happening
You describe
Where is the problem, and why?
Right optic nerve disease
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13/04/2012 78
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Direct reflex on right
Consensual reflex on
left
Note the pathway for light reflex
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Note the pathway for light reflex
Is this light reflex normal?
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Is this light reflex normal?
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Yes.
Note direct and
consensual lightreflex
I thi li ht fl l?
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Is this light reflex normal?
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Afferent path on lefteye is abnormal.
Efferent vs Afferent defect
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Efferent vs Afferent defect
Oculomotor Nerve CN III –
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Edinger - Westphal Nucleus• Location?
• Midbrain
• What is different about the things this nucleus, versus the oculomotor, projectsto?
• 1. Parasympathetic innervation – Synapse in ciliary ganglion, which leave as the short ciliary
– Note: The long ciliary nerve carries sensory fibers from the cornea (V1)and sympathetics to dilate the iris• 2. Smooth Muscles innervation
• Projects to?• Ciliary ganglion Ciliary Muscle
• Function = ?• Accomadation for near vision
• Sphincter pupillae• Function = ?• Constriction
– Both these are parasympathetic (constriction) and smooth muscle.
Ciliospinal reflex
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p
The ciliospinal reflex (pupillary-skin reflex)consists of dilation of the ipsilateral pupil inresponse to pain applied to the neck, face,and upper trunk.
If the right side of the neck is subjected to apainful stimulus, the right pupil dilates(increases in size 1-2mm from baseline).
This reflex is absent in Horner's syndrome
and lesions involving the cervical sympatheticfibers.Mediated by inhibitition of EW nucleus
Vis al Ac it
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Visual Acuity
• Newborn – 20/200, sees best in 2-75 cm range
• 3 months
– 20/60• 6 months
– 20/20
• 2 years – Acute near vision-fine motor skills develop
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• Toxic pupil –inneuromuscular blockde
• Adie’s tonic pupil– due tociliary gangilion block
• Paralytic pupil-inCN3nerve palsy
• Argyll Robertson pupil—pretectal nucleus lesion
• Marcus Gunn pupil—opticnerve involvement
Rotating Snake Illusion Effect: Illusory motion
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Kitaoka A, Ashida H (2003) Phenomenal characteristics of the peripheral drift illusion.VISION 15:261-262
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