Pupiliary Pathway

8/4/2019 Pupiliary Pathway

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DR R PATEL

Pupillary Pathway



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



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.



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.‖



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.



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)



Muscles of iris



Pupil

Normal size : 2-4mm

In dark adaption : 4.5-7 mm

In light adaption : 2.5-6 mm

Miosis : =/<3mm

Mydriasis : =/> 6mm



The pupil allows light to enter the posterior

segment of the eye.

The iris constricts or dilates to adjust size of the pupil.



Pupil Dilation and Constriction, Anterior View



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.



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.



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



Visual pathway

Optic nerve

Optic chiasma

Optic radiation

Lateral geniculate body

Visual area

Optic tract



Pretectal area

Accessory oculomotor nuclei

Occculomotor n.

Ciliary ganglia

Sphincter pupilCiliary muscle

Pupillary reflexes

A f h



Anatomy of theparasympathetic outflow



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)



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)



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.



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



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.



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



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



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).



Optic nerve

Optic chiasma

Optic tract

Lateral geniculatebody

Optic radiation

Visual area



The iris reflex



• 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.



• 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



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)



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



REFLEXES: Corneal Reflex

• Blinking – elicited by sensory stimulationof cornea

• A direct and consensual response

• Sensory: CNV1 (ophthalmic division oftrigeminal)

• Motor: CN VII (facial)



PUPIL



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



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



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



Why medieval Italian womenused Belladonna



Pupillary size assessment



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



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



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



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



RAPD or Marcus Gunn pupil

Examination of the pupils



Examination of the pupilsPERRL

P Pupils

E Equal

R Round

RL Reactive to Light



Horner’s Syndrome



Horner s SyndromePERRL

(Ptosis, Miosis and Anhydrosis)



• Sympathetic

Pathways to

the eye

n socor a



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



Irregular pupils

Argyl-Robertson

Possible other manifestation of CNS disease

BUT most commonly due to IntraocularCongenital AnomalyInflammation

TraumaSurgery

PERRL

Irregular Pupil after IOL



Irregular Pupil after IOLimplantation

P ill Li h R fl



Pupillary Light Reflex

PERRL



PERRL

Pupil Light ReflexesDirect Response – constriction of pupilwhen light shined into that eye

Consensual Response – constriction ofpupil of non-stimulated eye

Consensual Response of



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



Poor Pupil Reaction to Light

Diabetics

Neurologic DiseaseOptic Nerve Disease

Sign of possible serious ocular problemAcute Angle ClosureUveitis

Damage to Pupil fromSurgeryTrauma PERRL



Afferent Pupillary Defect

Swinging light test



Swinging light testAfferent Papillary Defect

R l ti Aff t P il D f t



Relative Afferent Pupil Defect

V.A. 20/20 20/20

Left RAPD

P ill APD



Pupillary exam: APD

sft.jpg

AFFERENT PUPILLARY

http://www.uak.medizin.uni-tuebingen.de/depii/groups/pupil/helmut/sft.jpg

http://www.uak.medizin.uni-tuebingen.de/depii/groups/pupil/helmut/sft.jpg



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



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



GRADING OF RAPD

1st animation



13/04/2012 77

Watch

I will describe what is happening

You describe

Where is the problem, and why?

Right optic nerve disease



13/04/2012 78



Direct reflex on right

Consensual reflex on

left

Note the pathway for light reflex



Note the pathway for light reflex

Is this light reflex normal?



Yes.

Note direct and

consensual lightreflex

I thi li ht fl l?



Afferent path on lefteye is abnormal.

Efferent vs Afferent defect



Efferent vs Afferent defect

Oculomotor Nerve CN III –



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



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

http://en.wikipedia.org/wiki/Pupil

http://en.wikipedia.org/wiki/Horner%27s_syndrome

http://en.wikipedia.org/wiki/Horner%27s_syndrome

http://en.wikipedia.org/wiki/Pupil



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



• 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



Kitaoka A, Ashida H (2003) Phenomenal characteristics of the peripheral drift illusion.VISION 15:261-262

Pupiliary Pathway

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