Pupillary pathways & reactions
Dr. C.R.Thirumalachar
• Pupillary constrictor/ spincter-innervated by
parasympathetic
• Pupillary dilator – innervated by sympathetic
• Evaluation of pupil- Diagnostic clue to ocular,
neurological, medical, surgical and paediatric
diseases
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
• 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
Light Reflex
Near relex
• Accomodation reflex:
• Stimulus : Blurring of retinal images when object
is near
• Retina- Optic nerve – Optic chiasma- Optic tractOptic 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
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
Accomodation Reflex
• 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
• 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
Sympathetic Pupillary system
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
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
-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 )
• 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)
• Horner’s syndrome :
– Involvement of cervical sympathetic
– Miosis, partial ptosis, enophthalmos & anhydrosis
– Iris heterochromia
• 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
• Hemianopic pupil ( wernicke’s 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
Hutchinson’s 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)
• Stage3 : Both pupils dilate. Stage of bilateral
paralysis. To assess pupil repeatedly is
important, therefore mydriatics should be
avoided in case of head injuries
• Adie’s 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 (Adie’s syndrome)
– Seen in young women
• Pupil in 3rd nerve palsy
– Dilated
– Non reactive
– Absolute motor paralysis
– Associated with ptosis, deviation of eyeball
• Pupil in diabetes
– Constricted
– Sluggishly reactive due to
• Glycogen infiltration of spincter
• Autonomic denervation
• Arteriosclerosis of radial iris vessels
Thank You