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The Pupillary Pathways ophthalmology.ppt
- 1. Pupillary pathways &reactions Dr. C.R.Thirumalachar
- 2. • Pupillary constrictor/spincter-innervated by parasympathetic • Pupillary dilator – innervated by sympathetic • Evaluation of pupil- Diagnostic clue to ocular, neurological, medical, surgical and paediatric diseases
- 3. 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
- 4. • A seconddecussation 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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- 6. Near relex • Accomodationreflex: • 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
- 7. Near reflex- convergencerelex • 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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- 9. • 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
- 10. • Emerge outof 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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- 12. 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
- 13. Marcus Gunn Pupil -Whenthe 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
- 14. -If light iskept 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 )
- 15. • Argyll Robertsonpupil(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)
- 16. • Horner’s syndrome: – Involvement of cervical sympathetic – Miosis, partial ptosis, enophthalmos & anhydrosis – Iris heterochromia
- 17. • Pourfour dePetit 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
- 18. • 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
- 19. Hutchinson’s pupil • Usefulin 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)
- 20. • Stage3 :Both pupils dilate. Stage of bilateral paralysis. To assess pupil repeatedly is important, therefore mydriatics should be avoided in case of head injuries
- 21. • Adie’s tonicpupil: 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
- 22. • Pupil in3rd nerve palsy – Dilated – Non reactive – Absolute motor paralysis – Associated with ptosis, deviation of eyeball
- 23. • Pupil indiabetes – Constricted – Sluggishly reactive due to • Glycogen infiltration of spincter • Autonomic denervation • Arteriosclerosis of radial iris vessels
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