Pupillary pathways & reactions

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 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

5. Light Reflex

6. 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- occipitomesencephalic tract- mid brain- E.W. nucleus- 3rd nerve- accessory ciliary ganglion along short ciliary nerves- ciliary muscle and pupil constrictor

7. 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

8. Accomodation Reflex

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 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

11. Sympathetic Pupillary system

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 -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

14. -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 )

15. 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)

16. Horner’s syndrome : • Involvement of cervical sympathetic • Miosis, partial ptosis, enophthalmos & anhydrosis • Iris heterochromia

17. 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

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 • 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)

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 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

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

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

24. Thank You