Pupillary pathways

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Pupillary pathways reactions

• Dr. C.R.Thirumalachar

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• Pupillary constrictor/ spincter-innervated by
  parasympathetic
• Pupillary dilator innervated by sympathetic
• Evaluation of pupil- Diagnostic clue to ocular,
  neurological, medical, surgical and paediatric
  diseases

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Light reflex Direct Consensual Afferent
pathway

• Initiated by retinal photoreceptors
• Transmitted along optic nerve
• Undergo a hemidecussation at the optic chiasma
  (nasal fibres cross over)
• Proceeds along optic tract
• Short of lateral geniculate body- enters midbrain
  via sup. Brachium of sup. Colliculus
• Synapses at pre- tectal nucleus
• Ends in both Edinger westpal nucleui

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• A second decussation occurs around aqueduct of
  sylvius
• Decussation at chiasma midbrain level between
  pretectal nucleus Edinger Westpal nucleus
  accounts for consensual light reflex
• E.W. nucleus (pupillo motor constrictor centre)
• Efferent fibres tract along 3rd nerve-nerve to
  inf. Obl.
• Enter the ciliary ganglion through its short
  motor root
• Synapse relay at ciliary ganglion
• Post ganglionic fibres reach ciliary muscle and
  iris spincter through short ciliary nerves

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Light Reflex
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Near relex

• Accomodation reflex
• Stimulus Blurring of retinal images when object
  is near
• Retina- Optic nerve Optic chiasma- Optic tract-
  Optic radiations- Lat geniculate body- visual
  cortex cortical association areas- occipito
  mesencephalic tract- mid brain- E.W. nucleus- 3rd
  nerve- accessory ciliary ganglion along short
  ciliary nerves- ciliary muscle and pupil
  constrictor

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Near reflex- convergence relex

• Co contraction of both medial recti
• Proprioceptive impulses originate and travel
  along 5th nerve
• Reach mesencephalic root of 5th nerve
• Transmitted to EWP nucleus in midbrain via
  convergence centre (Perlias N)
• From EWP efferent pathway same as accomodation
  reflex

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Accomodation Reflex
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• Dilator pathway
• Hypothalamic dilator centre - part of sympathetic
  system
• Descends through brainstem to the spinal cord
• C8- T2 segments of spinal cord cilio spinal
  centre of Budge

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• Emerge out of spinal cord enter paravertebral
  symp chain synapses sup cervical ganglion
• Symp plexus around carotid artery
• Enter cranial cavity along internal carotid
  artery
• Trigeminal ganglion ophthalmic division
  nasociliary nerve- long ciliary nerves- ciliary
  muscle and dilator pupillae

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Sympathetic Pupillary system
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Abnormal pupillary reactions

• RAPD
• RAPD seen in optic nerve retinal diseases with
  extensive retinal damage , gross macular lesions.
• Accurate quantification of RAPD (using neutral
  density filters) is accomplished by
  determination of the log unit difference needed
  to balance the pupil reaction between the 2 eyes

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• Marcus Gunn Pupil
• -When the contralateral/normal eye is
  covered, pupil on the affected side dilates
• -When the affected eye is covered pupil of
  the normal eye remains unaffected.
• Light is thrown on ipsilateral side(affected
  side)Ipsilateral direct reflex contralateral
  consensual reflex- sluggish and ill sustained.
• Light thrown on contralateral side (normal side)
  direct consensual (affected side) is normal
  well sustained

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• -If light is kept persistently on affected side,
  pupil may show initial sluggish contraction but
  contraction is ill sustained gradually shows
  paradoxical dilatation
• -Indicates conduction defect along efferent
  pathway (Optic nerve, Optic chiasma, part of
  optic tract, dorsal mid brain )

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• Argyll Robertson pupil(ARP)
• Occurs in neurosyphilis, Tabesdorsalis,G.P.I.
• Pupil is usually constricted ( involvement of
  descending sympathetic dilator fibres)
• Light reflex is absent
• Accomodation reflex , near reflex retained
• Site of lesion Pretectal nucleus. (dorsal mid
  brain)

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• Horners syndrome
• Involvement of cervical sympathetic
• Miosis, partial ptosis, enophthalmos anhydrosis
• Iris heterochromia

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• Pourfour de Petit Syndrome
• This syndrome is the clinical opposite of Horner
  syndrome. It represents oculosympathetic
  overactivity
• unilateral mydriasis, lid retraction, apparent
  exophthalmos, and conjunctival blanching
• Seen after trauma, brachial plexus anesthetic
  block or other injury, and parotidectomy

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• Hemianopic pupil ( wernickes pupil )
• Seen in optic tract lesions with hemianopia
• Stimulating the blind half of retina pupil shows
  no reaction
• Stimulating seeing half of retina pupil shows
  reaction
• Difficult to elicit due to scattering
  diffusion of light
• Use a narrow streak of light

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Hutchinsons pupil

• Useful in assessment of head injuries
• Stage1 Ipsilateral pupil (on the side of head
  injury shows contraction due to irritation,
  Contralateral (normal) pupil normal
• Stage2 Ipsilateral pupil shows dilatation due
  to paralysis , contralateral pupil constricts
  (irritation spreads to normal side)

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• Stage3 Both pupils dilate. Stage of bilateral
  paralysis. To assess pupil repeatedly is
  important, therefore mydriatics should be avoided
  in case of head injuries

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• Adies tonic pupil Characterised by
• large unilaterally dilated pupil
• Absent / poor light response
• In near response , there is slow / tonic
  contraction of the iris
• May be associated with loss of deep tendon
  reflexes (Adies syndrome)
• Seen in young women

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• Pupil in 3rd nerve palsy
• Dilated
• Non reactive
• Absolute motor paralysis
• Associated with ptosis, deviation of eyeball

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• Pupil in diabetes
• Constricted
• Sluggishly reactive due to
• Glycogen infiltration of spincter
• Autonomic denervation
• Arteriosclerosis of radial iris vessels

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• Thank You