Dr. Soundari from Dr. Agarwals Eye Hospital presenting a presentation on Visual pathway , in Kalpavriksha 2012 - Chennai

1. VISUAL PATHWAY
Dr.S.Soundari
Consultant Ophthalmologist
Dr Agarwal’s 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.

3. VISUAL PATHWAY

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]
Leber’s 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