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Visual pathway kHem
- 1. Presented By: Khemchand Sahu MBBSFinal Part I Guided By: Dr. Divya Verma Asst. Professor Dept. of Ophthalmology Lt. Shri Lakhiram Agrawal Memorial Medical College, Raigarh
- 2. Contents • Anatomy &Physiology of Visual Pathway • Lesions of the Visual Pathway • Pupillary Reflexes • Abnormalities of Pupillary Reflexes 28/11/2016 2Visual Pathway
- 3. Visual Pathway • Visualpathway or Optic Pathway is the nervous pathway that transmits impulses from retina to visual center in cerebral cortex • Components • Optic Nerve • Optic Chiasma • Optic Tract • Lateral Geniculate Bodies • Optic Radiations • Visual Cortex 28/11/2016 3Visual Pathway
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- 6. OPTIC NERVE • 2ndcranial nerve • Extent : optic disc to optic chiasma • 47-50 mm • Formation • Axons of ganglionic cells of retina 28/11/2016 6Visual Pathway
- 7. • Parts ofOptic Nerve • Intraocular part • Intraorbital part • Intracanalicular part • Intracranial part 28/11/2016 7Visual Pathway
- 8. • Intraocular part •1 mm • Starts from optic disc, pierces the choroid & sclera, converting it into sieve like structure Lamina Cribrosa • Intraorbital part • 30 mm • From back of the eyeball to optic foramina • Relation • Ant : Seperated from the ocular muscle by the orbital fat • Post : Closely surrounded by Annulus of Zinn • Retro bulbar Neuritis : Painful ocular movements
- 9. • Intracanalicular part •6-9 mm in length • Lies within the optic canal • Relation • Inferolateral : Ophthalmic artery • Medial : Ethmoid & Post. Ethmoid Sinus • Intracranial part • 10 mm • Lies above the cavernous sinus 28/11/2016 9Visual Pathway
- 10. OPTIC CHIASMA • Flattenedstructure • 12 mm horizontally, 8 mm anteroposteriorly • Lies over tuberculum & diaphargma sellae • Fibers originating from nasal halves of the retina decussate at the chiasma 28/11/2016 Visual Pathway 10 Optic Chiasma
- 11. OPTIC TRACT • Cylindricalbundle of nerve fibers • Runs outward & backward from posterolateral aspect of optic chiasma 28/11/2016 Visual Pathway 11 Optic Tract
- 12. LATERAL GENICULATE BODY •Oval structure • Situated at posterior termination of optic tract • Each geniculate body consists of 6 layers of neurons (Grey Matter) alternating with white matter 28/11/2016 12Visual Pathway Lateral Geniculate Body
- 13. OPTIC RADIATION • 3rdorder neuron • Extend from lateral geniculate body to visual cortex 28/11/2016 13Visual Pathway Optic Radiation
- 14. VISUAL CORTEX • Location: medial aspect of occipital lobe, above and below calcarine fissure • Areas • Primary Visual Area (Area 17) • Perception of visual impulses • Secondary Visual Area (Area 18) • Interpretation of visual impulses • Occipital Eye field (Area 19) • Concerned with movement of eye ball 28/11/2016 14Visual Pathway
- 15. Blood Supply ofOptic Nerve Head • Surface Layer : capillaries from retinal arterioles • Prelaminar region : Vessels of peripapillary choroid & lamina cribrosa • Lamina Cribrosa : posterior ciliary arteries, areterial circle of zinn • Retrolaminar part – Centrifugal branches of central retinal artery – Centrifugal branches from Pial plexus 28/11/2016 Visual Pathway 15
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- 17. 28/11/2016 17Lesions ofVisual Pathway
- 18. OPTIC NERVE LESION •Causes • Optic atrophy • Traumatic avulsion of optic nerve • Indirect optic neuropathy • Ischemic optic neuropathy • Acute optic neuritis • Clinical features 28/11/2016 18 Proximal Optic Nerve Lesion Distal Optic Nerve Lesion •Ipsilateral Blindness •Contralateral hemianopia •Abolition of direct light reflex on affected side & consensual on contralateral side •Near reflex is intact •Ipsilateral blindness •Abolition of direct light reflex on affected side & consensual on contralateral side •Near reflex is intact Lesions of Visual Pathway
- 19. CHIASMAL LESION • Causes –Intrinsic • Gliomas • Multiple sclerosis – Extrinsic : compressive lesion • Pituitary adenoma • Craniopharyngiomas • Meningiomas – Other • Metabolic • Toxic • Inflammatory 28/11/2016 19Lesions of Visual Pathway
- 20. Clinical feature ofchiasmal lesion • CHIASMAL SYNDROME 28/11/2016 20 Anterior Chiasmal Syndrome Affected part : Ipsilateral Optic Nerve fiber & Contralateral inferonasal fiber Junctional Scotoma Middle Chiasmal Syndrome Affected part : Decussating fibers in the body of chiasma Bitemporal hemianopia Posterior Chiasmal Syndrome Affected part : Caudal fiber Paracenbitemporal field defect Homonymous hemianopia on contralateral side Lesions of Visual Pathway
- 21. • LATERAL CHIASMALLESION • Causes • Distension of 3rd ventricle • Atheroma of the carotid or posterior communicating arteries • Features • Binasal Hemianopia 28/11/2016 21Lesions of Visual Pathway
- 22. OPTIC TRACT LESION •Causes • Intrinsic • Demyelinating diseases • Infarction • Extrinsic • Pituitary adenoma • Craniopharyngioma • Others • Syphilitic meningitis • Tubercular meningitis 28/11/2016 22Lesions of Visual Pathway
- 23. • Clinical Feature •Incongruous Homonymous Hemianopia • Wernicke’s reaction • Optic disc changes • Descending partial optic atropy : temporal pallor on side of lesion & bow-tie atrophy on contralateral side 28/11/2016 23Lesions of Visual Pathway
- 24. LESION OF LATERALGENICULATE BODY • Features • Homonymous Hemianopia • Normal pupillary reflexes • Optic disc pallor due to partial descending atrophy 28/11/2016 24Lesions of Visual Pathway
- 25. LESION OF OPTICRADIATION • Causes • Vascular occlusion • Tumor • Trauma • Temporal lobectomy 28/11/2016 25Lesions of Visual Pathway
- 26. • Features Visual Field Defect Superior Quadrantic Hemianopia Inferiorfibers involved Inferior Quadrantic Hemianopia Superior fibers involved Complete Homonymous Hemianopia Total fiber of optic radiation involved 28/11/2016 26Lesions of Visual Pathway
- 27. LESION OF VISUALCORTEX • Causes • Occlusion of posterior cerebral artery • Head injury 28/11/2016 27Lesions of Visual Pathway
- 28. • Visual FieldDefect • Congruous Homonymous hemianopia (sparing the macula) • Congruous Homonymous Macular defect • Bilateral Homonymous macular defect • Bilateral Homonymous Hemianopia with macula sparing • Other Manifestation • Cortical Blindness • Dyschromatopsia • Visual Hallucination • Palinopsia • Polyopsia Features 28/11/2016 28Lesions of Visual Pathway
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- 30. LIGHT REFLEX • Whenlight is shone in one eye both the pupils constricts. • Two Types: • Direct Light Reflex • Indirect (Consensual) Light Reflex • Constriction of pupil to which light is shone : Direct Light Reflex and that of other : Indirect Light Reflex 28/11/2016 30Pupillary reflexes
- 31. Afferent Fiber From retinato pretectal nucleus Internuncial Fiber Connects each pretectal nucleus with Edinger- Westphal Nuclei of both side Efferent Pathway From Edinger- Westphal nucleus to sphincter pupillae 28/11/2016 31Pupillary reflexes Pathway of light Reflex
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- 33. NEAR REFLEX • Occurson looking at near object • Two components • Convergence Reflex : Contraction of pupil on convergence • Accommodation Reflex : Contraction of pupil associated with accommodation 28/11/2016 33Pupillary reflexes
- 34. Pathway of NearReflex 28/11/2016 34Pupillary reflexes
- 35. PSYCHOSENSORY REFLEX • Dilatationof pupil in response to sensory & psychic stimuli 28/11/2016 35Pupillary reflexes
- 36. EXAMINATION OF PUPILLARYREFLEXES • Direct Light Reflex • Normal pupil reacts briskly & its constriction to light is well maintained • Consensual Light Reflex • Normally contralateral pupil should also constrict when light is thrown on to one pupil 28/11/2016 Pupillary reflexes 36
- 37. • Swinging FlashLight Test • Performed when relative afferent pathway defect is suspected in one eye • Normally, both pupil constrict equally & pupil to which light is transferred is tightly constricted • MARCUS-GUNN Pupil 28/11/2016 37Pupillary reflexes • Near Reflex • Pupil constrict while looking at near object
- 38. ABNORMALITIES OF PUPILLARY REACTIONS •AMAUROTIC LIGHT REFLEX • Absence of • Direct light reflex on affected side • Consensual light reflex on normal • Lesion : Optic Nerve, Retina of affected side 28/11/2016 38Pupillary reflexes • EFFERENT PATHWAY DEFECT • Absence of • Both direct & consensual light reflex on affected side • Presence of • Both direct & consensual light reflex on normal side • Cause : Sphincter paralysis Parasympatholytic Drug (Atropine) IIIrd nerve paralysis Internal Ophthalomoplegia AMAUROTIC PUPIL
- 39. • WERNICKE’S HEMIANOPICPUPIL • Light reflex is ABSENT • When light is thrown on temporal half retina of affected side & nasal half of opposite side • Light reflex is PRESENT • When light is thrown on nasal half of affected side & temporal half of opposite side • Lesion of optic tract • MARCUS-GUNN PUPIL • Seen in Relative Afferent Pupillary Defect (RAPD) • Affected pupil will dilate when light is moved from normal to abnormal eye • Earliest indication of optic nerve disease • Cause : Incomplete optic nerve lesion, Severe retinal disease • Test : Swinging Flash Light Test 28/11/2016 39Pupillary reflexes
- 40. • ARGYLL ROBERTSONPUPIL (ARP) • For both pupil • Reaction to near reflex : Present • But light reflex : Absent • Both pupil slightly small in size • Cause – Neurosyphilis in region of tectum 28/11/2016 40Pupillary reflexes
- 41. • ADIE’S TONICPUPIL • Reaction to • Light reflex : Absent • Near reflex : Very slow & tonic • Affected pupil is larger (Anisocoria) initially • Cause : Postganglionic parasympathetic pupillomotor damage • Constricts with weak Pilocarpine (0.125%), while normal does not 28/11/2016 41Pupillary reflexes
- 42. ANISOCORIA • Normal sizepupil : 3-4 mm • Difference between size of two pupil is called Anisocoria • Causes • Physiological • Pathological • Difference of 2 mm or more 28/11/2016 Pupillary reflexes 42
- 43. Pathological Anisocoria Abnormal Miosis Iridocyclitis HornerSyndrome Parasympathomimetic Drug Mydriasis Parasymapatholytic Drug Retinal Glaucoma 3rd nerve Paralysis
- 44. • Evaluation ofAnisocoria • Pupil Size • Anisocoria in dark & bright illumination : Physiological • Anisocoria greater in dim illumination : Horner Syndrome • Pupillary Light Reflex • Normal light reaction followed by dilatation lag : Horner Syndrome • Poor light reaction : Parasympathetic System Defect (3rd nerve palsy, tonic pupil, anti-cholinergic drug) 28/11/2016 44Pupillary reflexes
- 45. – Pharmacological Test: 28/11/2016 45 For suspected parasympathetic palsy : PILOCARPINE TEST Pupil Constrict to low conc. of pilocarpine (0.125%) • Adie’s Tonic Pupil Pupil Constrict to usual conc. of pilocarpine (1-2%) • 3rd nerve palsy Pupil does not constrict to pilocarpine • Pharmacological mydriasis For suspected sympathetic palsy Cocaine test (2-4%) • Small pupil fails to dilate in Horner Syndrome Hydroxyamphetamine test (1%) • Small pupil Dilate in Central & preganglionic and does not dilate in post ganglionic Horner syndrome Pupillary reflexes
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