studies of PHYSIOLOGY OF THE PUPIL.pptx

pupil physiology

1. Presenter ; Petros Desalegn (Ophthalmology Resident ) Moderator; Dr. Amare Atoma ( MD,Ophthalmologist ) JUDO,July,2021 8/2/2021 PHYSIOLOGY OF THE PUPIL 1 PHYSIOLOGY OF THE PUPIL

2. Outline 8/2/2021 PHYSIOLOGY OF THE PUPIL 2 Introduction Properties of light and pupil movement Pupillary reflexes Abnormalities of pupillay reflexes Afferent pathway defects Efferent pathway defects Pupillary light-near dissociation Sympathetic paresis Clinical comments Pharmacology of pupil Summary

3. Introduction 8/2/2021 PHYSIOLOGY OF THE PUPIL 3 Innervation Iris sphincter & ciliary muscle have PNS, receptor on the two muscle is muscarinic The postganglionic accommodative fibers supply the ciliary muscle. The postganglionic pupillary neurons innervate the iris sphincter muscle in a segmental distribution the ratio of accommodative fibers to pupillary fibers is 30  : 1, Dilator muscles are innervated by SNS, Receptor of iris dilator is mainly alpha adrenergic. sensory innervation Circulating catecholamines

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5. Ocular Sympathetic pathway 8/2/2021 PHYSIOLOGY OF THE PUPIL 5

6. P upil 8/2/2021 PHYSIOLOGY OF THE PUPIL 6 is a kinetic indicator of both ocular motor function and the retina, the special sensory apparatus that it serves. is situated slightly inferior and nasal to the center of the cornea. is the window to the inner eye, through which light passes to reach retinal photoreceptors.

7. Number of pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 7 Normally 1 pupil in each eye But there can be polycoria True Polycoria Pseudopolycoria Polycoria can result from:- iris hypoplasia in Axenfeld-Rieger syndrome(ARS) iridocorneal endothelial syndrome(ICE ) trauma surgery and persistent pupillary membranes.

8. 8/2/2021 PHYSIOLOGY OF THE PUPIL 8 Fig .ARS polycoria

9. Location of pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 9 It is found 0.5mm inferonasaly from center of the iris Rarely may be eccentric (Correctopia) Causes of correctopia Sector iris hypoplasia Colobomatous lesions ARS iridocorneal endothelial syndrome Ectopia lentis

10. Size of pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 10 Its size varies from 3-4mm depending on illumination Small at birth and largest during adolescent Dilates during stress and constricts during sleep are equal in both eyes ( Isocoria ) Can undergo constant fluctuation in its diameter(Pupillary unrest)

11. Disorders of pupil size 8/2/2021 PHYSIOLOGY OF THE PUPIL 11 Anisocoria Inequality in the diameters of the 2 pupils can be physiologic or pathologic

12. Shape of Pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 12 Normally circular in shape Dyscoria is an abnormal pupil shape It can result from C ongenital malformation like ARS Iridocyclitis Surgery

13. Color of pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 13 Normally greyish black Can be jet black like in aphakia Can be whitish which can occur due to RB ROP Coats disease Congenital cataract Persistent Fetal Vasculature

14. Functions of pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 14

15. Functions of pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 15

16. Clinical comment: optics and pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 16 After refractive surgery, younger patients usually have larger pupils in dim light compared with older individuals.

17. Properties of light and pupil movement 8/2/2021 PHYSIOLOGY OF THE PUPIL 17 As light intensity of the stimulus increases:- The amplitude of pupil movement increases The latency time of the pupil light reflex shortens With increasing duration of light stimulus, The contraction amplitudes become greater and more prolonged After an initial contraction, the pupil undergo oscillations ( hippus ) and slow dilation(pupil escape) due to light adaptation

18. 8/2/2021 PHYSIOLOGY OF THE PUPIL 18 Stimulus Property Effect on pupillary light reflex Light intensity Amplitude of contraction increases linearly over at least a 3 log unit range of stimulus intensity State of light adaptation In the dark-adapted state, the threshold light intensity needed to produce a pupil contraction becomes less Duration When stimulus duration is < 70 msec , there is a reciprocal r/p b/n the duration and intensity, w/c is required to produce a pupil contraction amplitude Perimetric location In photopic adaptation, the pupil responds greatest in the central field; the temporal field response > nasal field Spectral sensitivity A blue shift under dark adaptation and a peak sensitivity at green under photopic conditions Temporal frequency The normal pupil can’t move faster than 4 Hz b/c of the relatively slow contraction of smooth muscle Motion The pupil may respond to a motion stimulus even under isoluminant conditions Properties of light and pupil movement

19. Computerized pupillometry 8/2/2021 PHYSIOLOGY OF THE PUPIL 19 Help diagnosing causes of anisocoria (unequal pupils) when both pupils are recorded simultaneously

20. Pupil perimetry 8/2/2021 PHYSIOLOGY OF THE PUPIL 20 It records small pupil contractions in response to focal light stimuli placed in different perimetric location

21. Pupillary reflexes 8/2/2021 PHYSIOLOGY OF THE PUPIL 21 Light reflex Near reflex Darkness reflex Psycho-sensory reflex The lid closure reflex

22. 1.Light reflex 8/2/2021 PHYSIOLOGY OF THE PUPIL 22 When light is shone in one eye both the pupils constrict In normal subjects the direct and consensual reflexes are equal.. If both pupils are illuminated simultaneously, the response summates. Light reflex is initiated by rods and cones, bipolar neurons, and ganglion cells specially melanopsin containing ganglion cells.

23. Light reflex cont ….. 8/2/2021 PHYSIOLOGY OF THE PUPIL 23 The pupillary light reflex consists of :- ( 1) afferent division (2) interneuron and (3) efferent nerves

24. 8/2/2021 PHYSIOLOGY OF THE PUPIL 24 Fig . Light reflex pathway From Practical Ophthalmology: A Manual for Beginning Residents page, 128

25. Light reflex 8/2/2021 PHYSIOLOGY OF THE PUPIL 25 Receptive field properties of the pretectal interneurons . Two types of pretectal neurons Type 1 - A “flat” response Type 2 - “ foveal -weighted” response

26. Light reflex cont ….. 8/2/2021 PHYSIOLOGY OF THE PUPIL 26 Crossed and uncrossed pathways are almost equal, so:- Equal direct and consensual reflex Illuminating one eye does not result in anisocoria Input deficits to one eye caused by damage to the retina or ON does not produce an anisocoria Contraction anisocoria (Pseudo-RAPD) If crossed pathway slightly exceeds the uncrossed in both the chiasma and midbrain →slightly greater pupil response in the stimulated eye

27. Functions of light reflex 8/2/2021 PHYSIOLOGY OF THE PUPIL 27 1) Pupillary Constriction protects against excessive bleaching of visual pigments by reducing amount of light entering eye. 2) helps in light and dark adaptations.

28. 2.Near reflex 8/2/2021 PHYSIOLOGY OF THE PUPIL 28 When a person looks at a near target, 3 reactions normally occur: Accommodation Convergence Miosis

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30. Dark Reflex 8/2/2021 PHYSIOLOGY OF THE PUPIL 30 The pathway is presumed to be the same to reflex pathway Simply abolition of light reflex with consequent relaxation of the sphincter pupillae Contraction of dilator pupillae supplied by sympathetic nervous system

31. Dark Reflex Cont ….. 8/2/2021 PHYSIOLOGY OF THE PUPIL 31 supra-nuclear inhibition suppresses preganglionic parasympathetic output from the EWN → relaxation of the iris sphincter and pupil dilation . This inhibition is inactive during sleep, with anesthesia, or with narcotics use → miosis During a state of wakefulness, the supra-nuclear inhibition is active → mydriasis

32. When the pupil fails to dilate? 8/2/2021 PHYSIOLOGY OF THE PUPIL 32 Mechanical limitations of the pupil (scarring) Pharmacologic miosis . Aberrant re-innervation of cholinergic neurons to the iris sphincter that are not normally inhibited in darkness (accommodative or extraocular motor neurons). Lack of inhibitory input signal getting to the Edinger – Westphal nucleus. Lack of sympathetic input to the dilator muscle

33. Psycho-sensory reflexes 8/2/2021 PHYSIOLOGY OF THE PUPIL 33 Refers to dilatation of pupil in response to sensory and psychic stimuli. Not seen in newborn but appear in few days of life and fully developed by the age of six months. Their pathways still not elucidated but it is believed to be cortical. Results from two components; sympathetic discharge and inhibition of the parasympathetic discharge

34. The lid closure reflex 8/2/2021 PHYSIOLOGY OF THE PUPIL 34 Non specific term since lid closure may be accompanied by either dilatation or constriction. Constriction with blinking ; will not occur in dark so can be considerd as dark reflex Homolateral constriction with closure of the lid ; evoked if the lid is held open while effort of closure is made. Oculopupillary reflex ; dilatation with lid closure on touching the cornea

35. Abnormalities of pupillary reflexes 8/2/2021 PHYSIOLOGY OF THE PUPIL 35 Afferent pathway defects Total afferent pupillary defects(TAPD) or amaurotic pupil RAPD or Marcus Gunn pupil Werncke’s hemianopic pupil Efferent pathway defects Tonic pupil e.g Adies tonic pupil Pupillary light-near dissociation E .g Argyll Robertson pupil Sympathetic paresis E.g Horners syndrome

36. 1 . Afferent pathway defects 8/2/2021 PHYSIOLOGY OF THE PUPIL 36 Amaurotic pupil or TAPD Caused by complete optic nerve or retinal lesion leading to total blindness on the affected side . Characterized by: Absence of direct light reflex on affected side and loss of consensual light reflex on normal side When normal eye is stimulated both pupil react normally In diffuse illumination both pupil are equal Near reflex is normal in both eyes

37. Afferent pathway defects Cont… 8/2/2021 PHYSIOLOGY OF THE PUPIL 37 Relative afferent pupillary defects(RAPD) The pupil light reflex is symmetric between the two eyes of a normal individual Damage at any one of afferent input reduces the amplitude of pupil constriction T ypically caused by incomplete optic nerve lesion or severe retinal disease It is assessed by swinging flashlight test .

38. Afferent pathway defects Cont…. 8/2/2021 PHYSIOLOGY OF THE PUPIL 38 Normally both pupils constrict equally and the pupil to which light is transferred remains tightly constricted . The affected pupil will dilate ( paradoxical response) when the flashlight is moved from the normal eye to abnormal eye . The earliest indication of optic nerve disease even in the presence of normal visual acuity .

39. Causes of RAPD 8/2/2021 PHYSIOLOGY OF THE PUPIL 39 Lesions of Affarent optic Pathway Lesion of Optic nerve Optic neuritis Anterior Ischemic optic neuropathy Compressive optic neuropathy Glaucoma Retinal Diseases(lesions) Retinal detachment Ischemic diseasels like CRVO,CRAO,BRAO,BRVO Optic Chiasm Compression Craniopharyngioma Pituatry tumors

40. Quantitative grading of RAPD 8/2/2021 PHYSIOLOGY OF THE PUPIL 40 RAPD can be graded by:- Neutral Density Filter (NDF) Computerized pupillography

41. Afferent pathway defects Cont… 8/2/2021 PHYSIOLOGY OF THE PUPIL 41 The RAPD can be quantified in log units using neutral density filters placed in front of the better responding eye A log density filter that balances the asymmetry of pupil movement between the two eyes is taken as the log unit RAPD For example, a patient with a small amount of macular degeneration in one eye have only a 0.3 log unit RAPD. However , if that patient had a 1.0 log unit RAPD, previous branch retinal artery occlusion or optic neuropathy , would have to be considered

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43. Neutral density filter log units 8/2/2021 PHYSIOLOGY OF THE PUPIL 43 Grade Neutral density filter log units Grade 1 <0.6 Grade 2 0.6-0.9 Grade 3 1.2-1.5 Grade 4 >1.8 Source: Yotharac P ,Npat Aui-aree .Correlation between clinical grading and quantifications by Neutral Density filter of RAPD Jmed Asso . Thia 2012 ;95( Supple 4) :S92-9

44. 1. Afferent pathway defects 8/2/2021 PHYSIOLOGY OF THE PUPIL 44 Grading of RAPD Grade 1 – a weak initial pupillary constriction followed by greater redilation . Grade 2 – an initial pupillary stall followed by greater redilation . Grade 3 – an immediate pupillary dilation. Grade 4 – no reaction to light , Amaurotic pupil.

45. RAPD Video 8/2/2021 PHYSIOLOGY OF THE PUPIL 45

46. Afferent pathway defects Cont… 8/2/2021 PHYSIOLOGY OF THE PUPIL 46 Werncke’s Hemianopic pupil Indicates lesion in optic tract Stimulating blind half of retina ,Pupil shows no reaction. Stimulating seeing half of retina, pupil shows reaction. Difficult to elicit due to scattering and diffusion of light. Use narrow streak of light

47. Werncke’s Hemianopic pupil Cont.. 8/2/2021 PHYSIOLOGY OF THE PUPIL 47 Site of lesion Optic tract pupil hemianopic Optic atropy present Visual Field defect Hemianopia Pupil size Anisocoria with dilated pupil on affected side with ptosis

48. 2. Efferent pathway defects 8/2/2021 PHYSIOLOGY OF THE PUPIL 48 Characterized by absence of both direct and consensual light reflex on the affected side and presence of both direct and consensual light reflex on the normal side. Near reflex is also absent on the affected side The pupil is fixed and dilated leading to anisocoria on the affected side. If the iris sphincter is paretic, adding bright light tends to increase the anisocoria. Alternatively, if the iris dilator is paretic, the anisocoria is expected to increase as light is taken away because reflex dilation to darkness is impaired.

49. 2. Efferent pathway defects 8/2/2021 PHYSIOLOGY OF THE PUPIL 49 Common causes : Brainstem lesions at the level of the superior colliculus and red nucleus. Fascicular third nerve lesions; compressive third lesions classically have pupillary involvement. Lesions of the ciliary ganglion or short ciliary nerves. Iris damage; previous surgery, elevated IOP Drugs ; mydriatics agent

50. 2. Efferent pathway defects 8/2/2021 PHYSIOLOGY OF THE PUPIL 50 Tonic pupil Due to damage to the ciliary ganglion or short ciliary nerves Absent reaction to light Slow and tonic near reflex Cholinergic supersensitivity of the denervated muscle (constricts with 0.125% of pilocarpine while normal pupil does not) The affected pupil is larger

51. Tonic pupil cont.…… 8/2/2021 PHYSIOLOGY OF THE PUPIL 51 Causes of tonic pupil Local : infection ( e.g HZV),trauma, inflammation( Sarcoidosis ) or ischemia tumours ( congenital neuroblastoma ) Autonomic dysfunction : DM, chronic alcoholism, dysautonomias , neurosyphilis amyloidosis , sarcoidosis , Miller Fisher variant of GBS Idiopathic

52. 2. Efferent pathway defects 8/2/2021 PHYSIOLOGY OF THE PUPIL 52 The Adie’s tonic pupil Caused by denervation of the postganglionic supply of the sphincter pupillae and ciliary muscle of unknown etiology . Usually unilateral Typically affect healthy young women and it may be associated with absent knee jerk Affected pupil is large and irregular Light reflex absent and near slow. Accommodative paresis

53. Adie’s tonic pupil Cont…. 8/2/2021 PHYSIOLOGY OF THE PUPIL 53

54. 3.Pupillary light-near dissociation 8/2/2021 PHYSIOLOGY OF THE PUPIL 54 Any situation in which the pupillary near reaction is present and light reaction is absent Causes ;

55. Causes of pupillary light near dissociation cont …. 8/2/2021 PHYSIOLOGY OF THE PUPIL 55 Pseudo-Argyll Robertson pupil Peripheral neuropathies; DM, alcoholism, amyloidosis

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57. Argyll Robertson pupil(ARP ) 8/2/2021 PHYSIOLOGY OF THE PUPIL 57 Occurs in Neuro Syphilis i.e Tabes dorsalis Thought to be caused by lesion in the region of tectum dorsal midbrain interfering light reflex fibers and supranuclear inhibitory fibers Involvement is usually bilateral but asymmetric

58. ARP cont …. 8/2/2021 PHYSIOLOGY OF THE PUPIL 58 Pupil is usually constricted ( involvement of descending sympathetic dilator fibers) Light reflex is absent so light near dissociation Accommodation reflex , near reflex retained Pupils dilate very poorly with mydriatics

59. 4.Sympathetic paresis 8/2/2021 PHYSIOLOGY OF THE PUPIL 59

60. Sympathetic paresis Cont….. 8/2/2021 PHYSIOLOGY OF THE PUPIL 60 Horner’s syndrome Currently used to describe any oculo -sympathetic paresis Ptosis: mild (1-2mm) Upside down ptosis Miosis Ipsilateral facial anhidrosis if lesion is second order neuron. Dilation lag; Does not dilate with cocaine 4% Heterochromia irides ; when early in life enophthalmos Pupillary reaction is normal to light and near

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62. Pharmacologic diagnosis of Horner syndrome 8/2/2021 PHYSIOLOGY OF THE PUPIL 62 Cocaine 2% or 4% Cocaine blocks the reuptake of the NE that is released from the nerve endings Horner's pupil → interruption in the sympathetic pathway → no NE release → cocaine has no adrenergic effect so, no dilatation occur 45min after cocaine drops, anisocoria increases b/c the normal pupil has dilated more than the Horner's pupil A 0.8 mm of pupillary inequality after cocaine, Horner syndrome is likely

63. Pharmacologic diagnosis of Horner syndrome 8/2/2021 PHYSIOLOGY OF THE PUPIL 63 Apraclonidine 0.5% it has an advantage over cocaine in that it will actively dilate the affected eye and not the normal eye. positive ( mydriatic ) one in the affected eye rather than a negative one in the affected eye . Has two advantages over phenylephrine. Unlike phenylephrine, whose corneal penetration varies widely among individuals, apraclonidine readily penetrates the cornea. Phenylephrine needs to be diluted but apraclonidine does not need to be diluted.

64. Localization of Horner syndrome 8/2/2021 PHYSIOLOGY OF THE PUPIL 64 Using 10% Hydroxy amphetamine Acts by releasing NE from storage in the sympathetic postganglionic nerve endings. In postganglionic nerve damage, no NE stores available so, no dilation but will dilate the pupils in those with central or preganglionic lesions . Adrenaline test 10% Adrenaline 10% is instilled in both eyes Horners pupil due to postganglionic lesions dilate more than normal pupil because of denervation supersensitivity

65. Pourfour de Petit Syndrome 8/2/2021 PHYSIOLOGY OF THE PUPIL 65 Is clinical opposite of Horner syndrome. Represents oculosympathetic overactivity Unilateral mydriasis , lid retraction, apparent exophthalmos, and conjunctival blanching Seen after trauma, brachial plexus anesthetic block or other injury, and parotidectomy

66. Pupil-involving third nerve palsy 8/2/2021 PHYSIOLOGY OF THE PUPIL 66 If the pupillary light reaction is spared in the setting of a third nerve palsy, the palsy is probably not caused by compression or injury. But, more likely, it is caused by small vessel disease, such as might be seen in diabetes. Still definite number of pupil-sparing third nerve palsies are caused by midbrain infarcts and should have neuroimaging studies..

67. Pupil-involving third nerve palsy cont.. 8/2/2021 PHYSIOLOGY OF THE PUPIL 67 Compression on the medial side of the intracranial portion of the third nerve as it exits the midbrain involve the pupil. The most common cause are an aneurysm (i.e. of the posterior communicating artery) pituitary apoplexy (sudden lateral expansion of a pituitary adenoma pressing on the medial aspect of the third nerve). Dilated, non reactive, absolute motor paralysis associated with ptosis, deviation of eyeball

68. Hutchinson’s pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 68 Due to compression of oculomotor nerve on the side of mass lesion. 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

69. Summary of pupillary findings in clinical setting 8/2/2021 PHYSIOLOGY OF THE PUPIL 69

70. Pharmacology of the pupil 8/2/2021 PHYSIOLOGY OF THE PUPIL 70

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72. Miotics Parasympathomimetics 8/2/2021 PHYSIOLOGY OF THE PUPIL 72

73. Miotics 8/2/2021 PHYSIOLOGY OF THE PUPIL 73 Sympatolytics Alpha adrenergic blocker drugs such as thymoxamine , phenoxybenzamine and dibenamine Guanethidine is commonly used sympatholytic drug Prevent transmitter from affecting the dilator fibers Other miotics Histamine:- affects muscle fibers directly Morphine:- by cutting off cortical inhibition of Edinger westphal nucleus

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75. Mydriatics 8/2/2021 PHYSIOLOGY OF THE PUPIL 75 Sympathomimetics Act in 3 ways Increases NE release at presynaptic terminal Prevent its reuptake Directly stimulate dilator fibers Adrenalin Act on alpha receptor on dilator pupillae readily inactivated & not effective in normal eyes used in testing certain denervation syndromes in which dilation becomes hypersensitive

76. Mydriatics 8/2/2021 PHYSIOLOGY OF THE PUPIL 76 Phenylephrine Synthetic analogue of NE Stimulates the normal dilator in high concentration Cocaine Prevents reuptake of NE Activate dilator fibers Only adrenaline is effective when sympathetic nerve is paralyzed

77. Mydriatics 8/2/2021 PHYSIOLOGY OF THE PUPIL 77 Parasympatholytics Compete with Ach at NMJ Includes the drugs like :- Atropine Strongest mydriatic & cycloplegic . 1 % drop or ointment Complete dilation in 30-40’ & cycloplegia in 2hrs Its effect persists for ≥ a week Homatropine A 2% drop acts quickly than atropine Causes cycloplegia & mydriasis in 45’ staying for 48hrs

78. Mydriatics 8/2/2021 PHYSIOLOGY OF THE PUPIL 78 Cyclopentolate 1 % drop Short acting cycloplegic Causes mydriasis & cycloplegia in 1hr lasting 6-12 hrs Tropicamide 1% Quick & short acting(4–8 hours)

79. Summary 8/2/2021 PHYSIOLOGY OF THE PUPIL 79 Pupil is aperture at center( inferonasal ) of the iris. Its main functions are :- Control of Retinal Illuminations reduction of Optical Aberrations control depth of focus It is circular in shape and Isocoric bilatterally Has its own different reflexes like Light reflex, Near reflex,Darkness reflex,lid closure reflex and Psychosensory reflex

80. Flowchart for evaluation of anisocoria 8/2/2021 PHYSIOLOGY OF THE PUPIL 80

81. References 8/2/2021 PHYSIOLOGY OF THE PUPIL 81 Clinical anatomy and physiology of visual system 3 rd edition The AAO Basic and Clinical Science Course (BCSC ), 2019-2020 LWW, Duane’s Ophthalmology,2012.Edition. Adler’s physiology of the eye 11 th ed. Anatomy and physiology of eye, A.K.Khurana / Indu Khurana Kanski Clinical Ophthalmology, 9th Ed.chm Practical ophthalmology for beginning resident 7 th edition

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