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PUPIL - ANATOMY, PHYSIOLOGY AND REFLEXES
1. The pupil is a circular opening located in the center of the iris that regulates the amount of light entering the eye. 2. Pupil size and reaction are controlled by two sets of muscles - the sphincter pupillae constricts the pupil in response to light, and the dilator pupillae dilates the pupil under sympathetic stimulation. 3. Abnormalities in pupil size, shape, reaction to light and near response can indicate underlying pathologies affecting the complex neurological pathways and muscles that control the pupil. Assessment of pupillary reflexes is important for localizing lesions in the afferent visual pathways or efferent autonomic pathways.
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PUPIL - ANATOMY, PHYSIOLOGY AND REFLEXES
- 1. PRESENTER- DR. DAISYVISHWAKARMA, 2nd YR PG STUDENT DEPTT. OF OPHTHALMOLOGY, A.M.C.H.
- 2. PUPIL • Aperture atcentre of iris • Pierces the iris diaphragm slightly below and nasal to its centre, but lying on the optical axis behind the cornea
- 3. Function • Regulates theamount of light reaching the retina • To some extent, controls the amount of chromatic & spherical aberration in retinal images
- 4.
- 5. Anatomy Number : one Location: almost in centre of iris Shape : circular Colour : greyish- black
- 6. Size : 3-4mm 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 ( 1/10th of 1 mm. ) anisocoria maybe Anatomy
- 7. Anatomy Muscles : Size ofpupil is regulated by two muscles o iris
- 8. Development Formed by completeabsorption 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 ofPM vascularised Central part of PM completely absorbed forming the PUPIL Development
- 10.
- 11. Pupillary Pathways PATHWAY OFLIGHT REFLEX PATHWAY OF CONVERGENCE REFLEX PATHWAY OF ACCOMMODATION REFLEX PATHWAY OF SYMPATHETIC DISCHARGE
- 12. Pathway of LightReflex
- 13. Afferent Pathway Optic tract NasalFibers decussate in optic chiasm Travels centrally along the optic nerve Ganglion cells (1st ON) Rods and cones & Melanopsin Retinal Ganglion cells
- 14. The Accessory motornuclei of EW nucleus (2nd ON) New internuncial relay fibers partially cross over Pretectal Nucleus Midbrain from Lateral side of Superior colliculus
- 15. Efferent Pathway Located inferiorlyas it enters the orbit Passes laterally to petroclinoid ligament and dorsum sellae Lie on the superficial dorsomedial aspect as it leaves the brain stem (3rd ON) The axons of the EW nucleus extend into the IIIrd CN.
- 16. Inferior division of IIIrd CN Ciliary Ganglion (4th ON) ViaShort Ciliary N. Sphincter Pupillae
- 17. Pathway of ConvergenceReflex
- 18. Fibers from Medial Rectus viaIIIrd CN Mesencephalic nuc. of V CN Convergence Center in Tectal or Pre Tectal Region EW Nucleus Efferent fibers travel along IIIrd CN Relay in Accessory Ganglion Sphincter Pupillae
- 19. Pathway of AccommodationReflex
- 20. Pathway of AccommodationReflex Retina Via Optic nerve, Chiasma & Optic Tract Lateral Geniculate Body Striate Cortex From Para striate cortex Via Occipito- mesencephalic tract & pontine centre EW Nucleus Via III CN to Sphincter Pupillae
- 21. Pathway of SympatheticDischarge Posterior Hypothalamus 1st O.N within brainstem (uncrossed) Cilio-spinal Centre of Budge (C8-T2) 2nd O.N enter cervical sympathetic plexus Superior cervical sympathetic ganglion 3rd O.N – along I.C.A joins 5th CN Long Ciliary N. Ciliary body & Dilator pupillae
- 22.
- 23. PUPILLARY REFLEXES LIGHT REFLEX NEARREFLEX OTHER REFLEXES • DARKNESS REFLEX • PSYCHOSENSORY REFLEX • LID CLOSURE REFLEX
- 24.
- 25. NEAR REFLEX CONVERG ENCE OF VISUAL AXES CONSTRIC TIONOF PUPILS INCREASED ACCOMMODA TION TRIAD OF SYNKINETIC NEAR REFLEX COMPLEX
- 26. DARKNESS REFLEX Abolition oflight reflex – relaxation of sphincter pupillae Contraction of dilator pupillae – supplied by sympathetic nervous system
- 27. Dilatation of pupilin 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
- 28. Constriction of pupilassociated 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
- 29.
- 30.
- 31. D - shapedin Iridodialysis Festooned on dilatation in Posterior synaechia Pear shaped in Adherent Oval shaped in Glaucoma •SHAPE
- 32. Jet black pupil Aphakia Greyishwhite Cataract White reflex (leukocoria) Yellow reflex Endophthalmitis •COLOU R
- 33.
- 34. ANISOCORIAPHYSIOLOGI C Anisocoria• Mostly <0.4 mm. difference • Light & Darkness reflex normal • Topical Cocaine- equal dilatation • No associated symptoms MIOSIS Of One Pupil • Local miotics • Systemic morphine • Iridocyclitis • Horner’s syndrome • Pontine hemorrhage • Strong light • sleep MYDRIASIS Of One Pupil • Local mydriatics • Sphincter damage (glaucoma) • Internal ophthalmople gia • 3rd CN palsy • Belladona poisoning
- 35. ANISOCORIA Difference of pupilsize >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 –
- 36.
- 37. Abnormalities of Pupillary Reflexes AFFERENT PATHWAY DEFECTS TOTALAFFERENT PATHWAY DEFECT RELATIVE AFFERENT PATHWAY DEFECT WERNICKE’S HEMIANOPIC PUPIL EFFERENT PATHWAY DEFECTS TONIC PUPIL OCULOMOTOR NERVE PALSY PHARMACOLOGIC MYDRIASIS PUPILLARY LIGHT-NEAR DISSOCIATION ARGYLL ROBERTSON PUPIL SYMPATHETIC PARESIS HORNER’S SYNDROME
- 38. Total Afferent PathwayDefect (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
- 39.
- 40. • Weak initialconstriction & greater redilatationGrade I • Initial stall & greater redilatationGrade II • Immediate pupil dilatationGrade III • Immediate pupil dilatation following prolonged illumination of good eye for 6 sec Grade IV • Immediate pupil dilatation with no secondary constrictionGrade V Relative Afferent Pupillary Defect Marcus-Gunn Pupil Incomplete optic nerve lesion/ severe retinal disease Detected by Swinging Flashlight Test
- 41.
- 42. CAUS ES OPTIC NERVE DISORDERS • Opticneuritis • Ischemic optic neuropathies • Glaucoma • Traumatic optic neuropathy • Optic N compression • Optic atrophy • Surgical damage to N. RETINAL CAUSES • Ischemic retinal disease (CRVO, CRAO, BRAO) • Ischemic ocular disease • Retinal detachment • Severe macular degeneration • Severe retinal/ choroidal tumours • Retinitis – CMV, herpes simplex
- 43. Wernicke’s Hemianopic Pupil Optictract 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
- 44. Efferent Pathway Defects Brainstemlesions 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
- 45. Tonic Pupil Lesion ofCiliary 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)
- 46. Adie’s Tonic Pupil Idiopathictonic 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
- 47. Pupillary Light-Near Dissociation CAUSES B/LTAPD 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
- 48. Argyll Robertson Pupil Dorsalmidbrain lesion Cause – Neurosyphilis Usually B/L & assymetrical involvement Vision is good Pupils – small & irregular Light Reflex absent Near Reflex present
- 49. CENTRAL Horner’s Synd • Lesion located b/w hypothalam usto Ciliospinal centre of Budge (C8- T2) PREGANGLI ONIC Horner’s Synd • Lesion located b/w C8 - T2 to superior cervical ganglion POSTGANGLI ONIC Horner’s Synd • Lesion located b/w superior cervical ganglion to innervation of dilator pupillae Oculosympathetic paresis Horner’s Syndrome
- 50. Horner’s Syndrome PTOSIS INFERIOR PTOSIS MIOSIS PUPILLARYREACTIONS NORMAL DILATION LAG FACIAL ANHYDRIOSIS HETEROCHROMIA IRIDES
- 51. Paralysis Of Accommodation Cyclople gicdrugs Internal Ophthal mo- plegia Complet e 3Rd CN palsy
- 52. Paralysis Of Convergence HeadInjury Encephalitis Disseminated sclerosis Tumours WEBINO
- 53. Pupils in Trauma Uncalherniation with IIIrd CN entrapment in a comatose pt. Hutchinson’s Pupil • I/L pupil constricts due to irritation, C/L pupil remains normal Stage I • I/L pupil dilates due to paralysis, C/L pupil constricts due to irritation Stage II • Both pupils dilate due to paralysis Stage III
- 54. Pupils in Trauma •Pin-point pupil with retained light reflex PONS • Mildly dilated, not reacting to light MIDBRAIN • Horner’s SyndromeHYPOTHALAMUS • Widely dilated, immobile pupilCNS ANOXIA
- 55.
- 56. Drugs acting onPupil Miotics • Parasympathomim etic drugs • Sympatholytic drugs Mydriatics • Sympathomime tic drugs • Parasympathol ytic drugs
- 57. Miotics Parasympathomimetics/Cyclotonics (sphincter stimulators) • Directacting ( cholinergic agonists ) • PILOCARPINE • Indirect acting ( cholinesterase inhibitors ) • Reversible – PHYSOSTIGMINE • Irreversible – ECOTHIOPHATE IODIDE, etc. • Dual action Sympatholytics (block dilator activity) • Alpha adrenergic blockers • GUANETHIDINE, PHENOXYBENZAMINE
- 58. Mydriatics Sympathomimetics (dilator stimulators) •EPINEPHRINE • PHENYLEPHRINE • HYDROXYAMPHETAMINE, EPHEDRINE • COCAINE, APRACLONIDINE Parasympatholytics/Cycloplegics (block sphincter activity) • ATROPINE • HOMATROPINE • CYCLOPENTOLATE • TROPICAMIDE
- 59. Pharmacological Tests Miotic pupildilatation – 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%) TestDilatation to apraclonidine – Horner’s syndrome Phenylephrine (1%) TestDilatation to phenylephrine – only post- ganglionic Horner’s syndrome
- 60. Pilocarpine Test Pupil constriction to0.125% pilo • Adie’s tonic pupil Pupil constriction to 1 – 2% pilo • 3rd CN palsy No constriction with pilo • Mydriatic drugs • Traumatic mydriasis • Fixed pupils in Iritis
- 61.
- 62. LIGHT-NEAR DISSOCIATION BILATERAL -CONVERGENCE- RETRACTION NYSTAGMUS -VERTICAL GAZEDEFICIT -CONVERGENCE DEFICIT -LID RETRACTION PARINAUD SYNDROM E UNILATERA L -SEGMENTAL PUPILLARY CONSTRICTION -IMPAIRED DARK ADAPTATION –IMPAIRED NEAR REFLEX –TONIC REDILATION BILATERA L ADIE’S PUPIL UNILATERA L ADIE’S PUPIL
- 63. NO LIGHT-NEAR DISSOCIATION 0.125% PILOCARPINE CONSTRICTI ON RECHECK FOR TONIC PUPILS NO RESPONSE 1%PILOCARPINE CONSTRICTIO N 3RD CN PALSY NO RESPONSE DRUG- INDUCED
- 64. MIOSIS NORMAL LIGHT REACTION 4% COCAI NE DILATION ESSENTIAL ANISOCORI A NO RESPONS E HORNER SYMPATHETIC PARESIS -ABNORMAL LIGHT REACTION -IRRREGULARPUPIL -LIGHT-NEAR DISSOCIATION ARGYLL ROBERTSON PUPILS
- 65. HORNER SYMPATHETIC PARESIS 1% HYDROXYAMPHETAM INE DILATIO N CENTRAL / PREGANGLIO NIC LESION NO RESPON SE POSTGANGLI ONICLESION HETEROCHRO MIA IRIDIS CONGENITAL HORNER’S SYNDROME
- 66. Conclusion The pupil isa 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