PUPIL - ANATOMY, PHYSIOLOGY AND REFLEXES

The anatomy and physiology of the human pupil and the pupillary reflexes.

1. PRESENTER- DR. DAISY VISHWAKARMA, 2 nd YR PG STUDENT DEPTT. OF OPHTHALMOLOGY, A.M.C.H. PUPIL - ANATOMY, PHYSIOLOGY & REFLEXES

2. PUPIL Aperture at centre of iris P ierces the iris diaphragm slightly below and nasal to its centre, but lying on the optical axis behind the cornea

3. Function Regulates the amount of light reaching the retina To some extent, controls the amount of chromatic & spherical aberration in retinal images

4. ANATOMY of PUPIL

5. Anatomy Number : one Location : almost in centre of iris Shape : circular Colour : greyish -black

6. Size : 3-4 mm Between 1.5 and 8 mm depending upon illumination Variation with age : small at extremes of age Physiological changes : dilate – emotional stress; constrict – sleep Isocoria : both of equal size; slight ( 1/10 th of 1 mm. ) anisocoria maybe found Anatomy

7. Anatomy Muscles : Size of pupil is regulated by two muscles of iris

8. Development Formed by complete absorption of the central part of pupillary membrane Pupillary membrane is formed by the mesodermal tissue surrounding the margin of the optic cup and tunica vasculosa lentis .

9. Peripheral part of PM vascularised Central part of PM completely absorbed forming the PUPIL Development

10. PHYSIOLOGY Of PUPIL

11. Pupillary Pathways

12. Pathway of Light Reflex

13. Afferent Pathway

14. Efferent Pathway

15. Pathway of Convergence Reflex

16. Pathway of Accommodation Reflex

17. Pathway of Accommodation Reflex

18. Pathway of Sympathetic Discharge

19. PUPILLARY REFLEXES

20. PUPILLARY REFLEXES

21. LIGHT REFLEX

22. NEAR REFLEX TRIAD OF SYNKINETIC NEAR REFLEX COMPLEX

23. DARKNESS REFLEX Abolition of light reflex – relaxation of sphincter pupillae Contraction of dilator pupillae – supplied by sympathetic nervous system

24. Dilatation of pupil in response to sensory & psychic stimuli Fully developed by 6 months of age Pathways – unknown Two components – Sympathetic discharge to dilator pupillae muscle Inhibition of parasympathetic discharge to sphincter pupillae muscle PSYCHOSENSORY REFLEX

25. Constriction of pupil associated with blinking – type of darkness reflex Homolateral pupillary constriction associated with closure of lid – attempt at near gaze Pupillary dilatation associated with lid-closure on touching the cornea ( oculopupillary reflex) – type of psychosensory reflex LID CLOSURE REFLEX

26. MORPHOLOGICAL ABNORMALITIES OF PUPIL

27. SHAPE

28. COLOUR

29. SIZE ISOCORIA ANISOCORIA MIOSIS MYDRIASIS

30. ANISOCORIA

31. ANISOCORIA Difference of pupil size >2mm. – Pathological Sign of Autonomic dysfunction NOT caused by an Optic N. / afferent pupillary dysfunction ANISOCORIA SAME IN BRIGHT / DIM ILLUMINATION – physiological anisocoria ANISOCORIA INCREASES IN BRIGHT ILLUMINATION – Larger pupil in abnormal – parasympathetic palsy ANISOCORIA INCREASES IN DIM ILLUMINATION – smaller pupil is abnormal – sympathetic palsy.

32. ABNORMALITIES OF PUPILLARY REFLEXES

33. Abnormalities of Pupillary Reflexes

34. Total Afferent Pathway Defect (TAPD) Amaurotic Pupil Complete optic nerve / retinal lesion PL – ve eye STIMULATING NORMAL EYE – Both pupils react normally STIMULATING AFFECTED EYE – No direct light reflex on affected side No consensual light reflex on normal side Diffuse illumination – equal size pupils Near reflex – normal in both eyes

35. Amaurotic Pupil (TAPD)

36. Relative Afferent Pupillary Defect Marcus-Gunn Pupil Incomplete optic nerve lesion/ severe retinal disease Detected by Swinging Flashlight Test

37. Marcus-Gunn Pupil (RAPD)

38. CAUSES

39. Wernicke’s Hemianopic Pupil Optic tract lesion LIGHT REFLEX ABSENT on stimulating – Affected side – temporal half of retina Opposite side – nasal half of retina LIGHT REFLEX PRESENT on stimulating – Affected side – nasal half of retina Opposite side – temporal half of retina

40. Efferent Pathway Defects Brainstem lesions Fascicular Third Cranial Nerve lesions – compressive third nerve lesions Lesions of Ciliary Ganglion / Short Ciliary Nerves Iris damage Mydriatic Drug COMMON CAUSES STIMULATING AFFECTED EYE – Direct light reflex & near reflex absent Consensual reflex present STIMULATING NORMAL EYE – Direct light reflex & near reflex present Consensual reflex absent

41. Tonic Pupil Lesion of Ciliary Ganglion / Short Ciliary Nerves AFFECTED PUPIL Is larger Reaction to light – absent Near Reflex – very slow & tonic Accommodative paresis Cholinergic supersensitivity of denervated muscle (constricts with 0.125% pilocarpine )

42. Adie’s Tonic Pupil Idiopathic tonic pupil with benign areflexia Denervation of postganglionic supply of sphincter pupillae & ciliary muscles of unknown etiology 80% U/L Affects healthy young women > men Absent knee jerk

43. Pupillary Light-Near Dissociation CAUSES B/L TAPD Lesions in midbrain TNP with aberrant regeneration of medial rectus innervation into sphincter innervation pathway Ciliary ganglion/ short ciliary nerve lesions with aberrant regeneration of accomodation

44. Argyll Robertson Pupil Dorsal midbrain lesion Cause – Neurosyphilis Usually B/L & assymetrica l involvement Vision is good Pupils – small & irregular Light Reflex absent Near Reflex present Cocaine Test- mydriasis

45. Oculosympathetic paresis Horner’s Syndrome

46. Horner’s Syndrome

47. Paralysis Of Accommodation

48. Paralysis Of Convergence

49. Pupils in Trauma Uncal herniation with IIIrd CN entrapment in a comatose pt. Hutchinson’s Pupil

50. Pupils in Trauma

51. PHARMACOLOGY OF PUPIL

52. Drugs acting on Pupil

53. Miotics

54. Mydriatics

55. Pharmacological Tests Miotic pupil dilatation – central & preganglionic Horner’s syndrome No dilatation – post- ganglionic Horner’s syndrome Cocaine (4%) Test Hydroxyamphetamine (1%) Test No dilatation to 4% cocaine – Horner’s syndrome Apraclonidine (0.5%) Test Dilatation to apraclonidine – Horner’s syndrome Phenylephrine (1%) Test Dilatation to phenylephrine – only post- ganglionic Horner’s syndrome

56. Pilocarpine Test

57. Conclusion The pupil is a very important structure in the human eye. It regulates the amount of light entering the eye. It improves the optical quality of the image formed on the retina by reducing the optical aberrations. It increases the depth of focus. It also allows flow of aqueous humour from posterior to anterior chamber. Knowledge of the normal & abnormal functioning of the pupils is very essential to diagnose several ocular, neurological & systemic disorders.