Visual pathway
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Dr. Soundari from Dr. Agarwals Eye Hospital presenting a presentation on Visual pathway , in Kalpavriksha 2012 - Chennai
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Visual pathway
- 1. VISUAL PATHWAY Dr.S.Soundari Consultant Ophthalmologist Dr Agarwalâs Eye Hospital Chennai
- 2. Optic nerve is an outgrowth of the brain Its fibers posses no neurolemmal cells Surrounded by meninges unlike any peripheral nerves Both the primary and second order neurons are in the retina.
- 6. Optic nerve Intraocular part Intraorbital part Intracanalicular part Intracranial part
- 18. OPTIC NERVE LESION & FIELD DEFECTS
- 19. Optic nerve field defects Central scotoma Enlargement of blind spot Arcuate field defects Altitudinal field defects
- 20. Paillomacular bundle Macular fibres enter the temporal aspect of the disc. Defect can lead to Central scotoma Centrocecal scotoma Paracentral scotoma
- 21. Causes for central scotoma Demylineation[retrobulbar neuritis] Leberâs hereditary optic neuropathy Toxins- tobacco,lead,alcohol,methanol Vitamin B12 deficiency
- 23. Enlargement of blind spot
- 24. Altitudinal field defect Ischaemic optic neuropathy Branch retinal artery occlusion Inferior retinal coloboma
- 26. CHIASMAL LESION & FIELD DEFECTS
- 27. Chiasma Lower nasal fibres cross low and anteriorly Upper nasal fibres cross high and posteriorly Macular fibres also cross in the posterior part of the chiasm.
- 29. Location of chiasma Central fixation -80%- above the sella Pre fixed chiasm-10%-located anteriorly- so pitutary tumour involves the optic tract first [lower temporal fields first] Post fixed chiasm-10%-located posteriorly- so optic nerve gets involved first [upper temporal fields first]
- 32. Pitutary adenoma Visual fields ; bitemporal hemianopia,junctional scotoma, bitemporal hemianopic scotoma Colour vision; early red deficit Visual acuity tends to reduce Optic disc- bow tie atrophy rarely papilloedema Extraocular movements: cranial nerve palsies,see saw nystagmus,spasm nutans.
- 33. hemifield slip- due to the failure of controlling phoria by fusion. Post fixation blindness.
- 38. Pseudo bitemporal hemianopia Bilateral sectoral retinitis pigmentosa Tilted disc Bilateral inferotemporal retinoschsis.
- 39. OPTIC TRACT LESIONS & ITS FIELD DEFECTS
- 40. OPTIC TRACT Carries ipsilateral temporal fibres and controlateral nasal fibres and pupillary fibres. So right optic tract lesion will cause left homonymous hemianopia
- 42. ASSOCIATIONS Controlateral pyramidal signs. Incongruous homonymous hemianopia. Wernicke's hemianopic pupil Optic atrophy
- 43. OPTIC RADIATION AND ITS FIELD DEFECTS
- 44. OPTIC RADIATIONS The corresponding retinal elements lie progressively closer, so congruous hemianopia. Passes through the temporal lobe and pareital lobe and ends in the visual cortex.
- 45. TEMPORAL LOBE Controlateral congruous homonymous superior quadrantanopia[pie in the sky] Controlateral hemisensory disturbance Mild hemiparesis Paraxysomal olfactory and uncinate fits. Formed visual hallucinations
- 46. Pie in the sky
- 47. PAREITAL LOBE Controlateral congruous homonymous inferior quadrantanopia[pie on the floor] Visual perception difficulties Right-left confusion Acalculia Assymmetric OKN.[OKN response diminished towards the side of the lesion.]
- 48. Pie on the floor
- 49. Striate calcarine cortex Congruous homonymous hemianopias with macular sparing, macular involvement alone. Formed visual hallucinations. Anton's syndrome[ denial of blindness] Riddoch phenomenon
- 52. THANK YOU