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OPTIC PATHWAY AND
LESIONS
UMA CHIDIEBERE JOHN
• Beginning in the retina, the visual pathway continues
• through the optic nerves,
• optic chiasm,
• and optic tracts to ...
• A healthy disc is normally pink to
orange in color, with well
delineated margins and a small
cup to disc ratio (<0.3)
3
Why the normal disc is pink?
• Thickness and the
cytoarchitecture of fiber bundles
passing between glial columns
containin...
• The retina is a thin, multilayered tissue sheet containing
three developmentally distinct, interconnected cell groups
th...
Receptors:
1. Rods
2. Cones
Neurons:
1. First order: bipolar cells
2. Second order: ganglion cells
3. Third order: LGB
Vis...
Components of the visual pathway
A. Optic nerve
B. Optic chiasma
C. Optic tracts
D. Lateral geniculate bodies
E. Optic rad...
VISUAL PATHWAY
Visual
Pathway
Optic chisam
• Floor of the third ventricle.
• 5-10 mm above the diphragma sella and the hypophysis cerebri.
• 12mm wide, ...
1. OPTIC
NERVE
(STUMP)
2. 0PTIC
CHIASMA
3. OPTIC
TRACTS
Visual
Pathway
Optic chiasma:
1. Junction of the floor and
the anterior wall of the
third ventricle
2. Rests on the diaphr...
13
OPTIC TRACTS
• Cylindrical bundle of nerve
fibres.
• Run outwards & backwards
from posterolateral aspect of
optic chiasma ...
Visual
Pathway
Optic tracts:
1. Medial root
Gudden’s commisure
2. Lateral root
a. LGB
b. Superior colliculus &
pre-tectal ...
Visual
Pathway
Lateral geniculate body:
1. Part of meta-thalamus
2. Connected to superior
colliculus via superior
brachium...
OPTIC RADIATIONS (Geniculo-Calcarine
Pathway)
• From LGB to the occipital cortex.
• Pass forwards then laterally through t...
Visual
Pathway
Optic radiation:
1. From LGB to striate area
of visual cortex (17)
2. Passes through the retro-
Lentiform p...
Primary Visual Cortex????
• Area 17
• located in the occipital
lobe in the calcarine
fissure region extending
to the pole
...
primary VISUAL CORTEX
• FROM THE LATERAL GENICULATE NUCLEUS, THE FIBRES PASS BY THE
OPTIC RADIATIONS TO THE PRIMARY VISUAL...
Secondary Visual Areas
• visual association cortex (area
18, 19)
• responsible for analyzing the
visual information
• area...
Retinal Projections to Subcortical
Regions
• suprachiasmatic nucleus of the
hypothalamus
• control of circadian rhythms??
...
The Autonomic Nerves to the Eyes
23
The Autonomic Nerves to the
Eyes
• The eye is innervated by both parasympathetic and
sympathetic neurons.
• Parasympatheti...
Control of Pupillary Diameter
• miosis: decreasing of pupillary
aperture due to stimulation of
parasympathetic nerves that...
Fig.
16.07
26
Visual reflexes
• Light reflex or pupillary
reflex:
When light is shown to one
eye, normally the pupils of
both eyes const...
Pathways of direct and indirect light reflexes
(v.imp.)
29
Pupillary light reflex
Direct
Consensual
Accommodation
ACCCOMODATION REFLEX
• When the eyes are focussed
from a distant to near
object, three reactions take
place
• 1. Constrict...
Accommodation
reflex
LESIONS OF THE VISUAL PATHWAY
Optic nerve lesions (A,B)
Causes : Optic atrophy, traumatic avulsion, acute optic neuritis etc.
1.Distal optic nerve lesio...
2. Proximal optic nerve lesion (B)
• Blindness on affected side
• Contralateral hemianopia
• Abolition of direct light ref...
Chiasmal lesions (C,D)
1.Central chiasmal lesion (C)
• Bitemporal hemianopia
• Bitemporal hemianopic paralysis of pupillar...
Causes :
I. Intrinsic causes – Lesions which produce thickening of
chiasma. Eg. Gliomas, multiple sclerosis
II. Extrinsic ...
Optic tract lesions (E)
Causes :
I. Intrinsic causes – Demyelinating diseases and infarction.
II. Extrinsic causes – Compr...
Optic tract lesions
• Incongruous homonymous hemianopia
• Contralateral hemianopic pupillary responses (Wernicke’s
reactio...
Pitutary adenoma
• Visual fields ; bitemporal hemianopia,junctional
scotoma,
bitemporal hemianopic scotoma
• Colour vision...
Lateral geniculate nucleus lesions(E)
• Incongruous homonymous hemianopia
• Pupillary reflexes are normal as the fibres go...
Lesions of optic radiations (F,G)
Common lesions include :
• Vascular occlusions
• Tumours
• Trauma
• Temporal lobectomy f...
Lesions of optic radiations
• Superior quadrantic hemianopia(F) – Pie in the sky lesions.
It is explained by the fact that...
• Complete homonymous hemianopia(H) – produced when
all fibres of optic radiations are involved sometimes sparing
the macu...
Visual cortex lesions (I,J,K)
• Congruous homonymous hemianopia – macular field of vision is
spared. It is a feature of oc...
• Bilateral homonymous macular defects – presenting like
bilateral central scotoma occur in bilateral lesions of
occipital...
• Visual hallucinations
• Palinopsia – Persistent perception of visual image
• Visual anesthesia – transposition of visual...
Optic pathway and lesions
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Optic pathway and lesions

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Neurology, ophthalmology, optic pathway anatomy, and lesions

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Optic pathway and lesions

  1. 1. OPTIC PATHWAY AND LESIONS UMA CHIDIEBERE JOHN
  2. 2. • Beginning in the retina, the visual pathway continues • through the optic nerves, • optic chiasm, • and optic tracts to synapse in • the lateral geniculate nucleus (LGN). • From the LGN, it extends through • the temporal and parietal lobes • to terminate in the occipital lobes
  3. 3. • A healthy disc is normally pink to orange in color, with well delineated margins and a small cup to disc ratio (<0.3) 3
  4. 4. Why the normal disc is pink? • Thickness and the cytoarchitecture of fiber bundles passing between glial columns containing capillaries 4
  5. 5. • The retina is a thin, multilayered tissue sheet containing three developmentally distinct, interconnected cell groups that form signal processing networks: • • Class 1 :: sensory neuroepithelium (SNE) :: photoreceptors and BCs • • Class 2 :: multipolar neurons :: GCs, ACs, and axonal cells (AxCs) • • Class 3 :: gliaform neurons :: horizontal cells (HCs)
  6. 6. Receptors: 1. Rods 2. Cones Neurons: 1. First order: bipolar cells 2. Second order: ganglion cells 3. Third order: LGB Visuo-striate area (17): Both walls of calcarine sulcus involving Cuneus and lingual gyrus
  7. 7. Components of the visual pathway A. Optic nerve B. Optic chiasma C. Optic tracts D. Lateral geniculate bodies E. Optic radiations F. Visual cortex
  8. 8. VISUAL PATHWAY
  9. 9. Visual Pathway
  10. 10. Optic chisam • Floor of the third ventricle. • 5-10 mm above the diphragma sella and the hypophysis cerebri. • 12mm wide, 8mm A-P , 4 mm thick. • Important relations: 3rd ventricle, hypothalmus, pituitary stalk, sella, dorsum sellam anterior and posterior clinoid processes, cavernous sinus. • Nasal fibers cross ; temporal fibers do not (53:47). • Wilband’s knee.
  11. 11. 1. OPTIC NERVE (STUMP) 2. 0PTIC CHIASMA 3. OPTIC TRACTS
  12. 12. Visual Pathway Optic chiasma: 1. Junction of the floor and the anterior wall of the third ventricle 2. Rests on the diaphragma sellae 3. Wilbrand’s loop
  13. 13. 13
  14. 14. OPTIC TRACTS • Cylindrical bundle of nerve fibres. • Run outwards & backwards from posterolateral aspect of optic chiasma ,between tuber cinereum & anterior perforated substance to unite with cerebral peduncle. • Fibres from temporal half of retina of same eye & nasal half of opposite eye. • Posteriorly each ends in Lateral Geniculate Body.
  15. 15. Visual Pathway Optic tracts: 1. Medial root Gudden’s commisure 2. Lateral root a. LGB b. Superior colliculus & pre-tectal nucleus c. Supra-chiasmatic nucleus
  16. 16. Visual Pathway Lateral geniculate body: 1. Part of meta-thalamus 2. Connected to superior colliculus via superior brachium 3. Cells arranged in six layers
  17. 17. OPTIC RADIATIONS (Geniculo-Calcarine Pathway) • From LGB to the occipital cortex. • Pass forwards then laterally through the area of wernicke as optic peduncles. • Anterior to lateral ventricle ,traversing the retrolenticular part of internal capsule,medial to auditory tract. • Its fibres then spread out fanwise to form medullary optic lamina. • Inferior fibres subserve upper visual fields & sweep anteroinferiorly in meyer’s loop & temporal lobe to visual cortex. • Superior fibres subserve inferior visual field proceed posteriorly through parietal lobe to visual cortex.
  18. 18. Visual Pathway Optic radiation: 1. From LGB to striate area of visual cortex (17) 2. Passes through the retro- Lentiform part internal capsule 3. Meyer’s loop
  19. 19. Primary Visual Cortex???? • Area 17 • located in the occipital lobe in the calcarine fissure region extending to the pole • large representation in visual cortex for the macula (region for highest visual acuity) • receives the primary visual input 19
  20. 20. primary VISUAL CORTEX • FROM THE LATERAL GENICULATE NUCLEUS, THE FIBRES PASS BY THE OPTIC RADIATIONS TO THE PRIMARY VISUAL CORTEX. • IT IS LOCATED IN THE CALCARINE FISSURE AREA OF THE MEDIAL OCCIPITAL LOBE. (BRODMANN’S AREA 17 OR V1)
  21. 21. Secondary Visual Areas • visual association cortex (area 18, 19) • responsible for analyzing the visual information • area for 3 dimensional position, gross form, and motion • area for color analysis 21
  22. 22. Retinal Projections to Subcortical Regions • suprachiasmatic nucleus of the hypothalamus • control of circadian rhythms?? • pretectal nuclei • pupillary light reflex • accommodation of the lens • superior colliculus • rapid directional movement of both eyes 22
  23. 23. The Autonomic Nerves to the Eyes 23
  24. 24. The Autonomic Nerves to the Eyes • The eye is innervated by both parasympathetic and sympathetic neurons. • Parasympathetic fibers arise in the Edinger-Westphal nucleus, pass in the 3rd cranial nerve to the ciliary ganglion. • Postganglionic fibers excite the ciliary muscle and sphincter of the iris. • Sympathetic fibers originate in the intermediolateral horn cells of the superior cervical ganglion. • Postganglionic fibers spread along the corotid artery and eventually innervate the radial fibers of the iris. 24
  25. 25. Control of Pupillary Diameter • miosis: decreasing of pupillary aperture due to stimulation of parasympathetic nerves that excite the pupillary sphincter muscle • mydriasis: dilation of pupillary aperture due to stimulation of sympathetic nerves that excite the radial fibers of the iris 25
  26. 26. Fig. 16.07 26
  27. 27. Visual reflexes • Light reflex or pupillary reflex: When light is shown to one eye, normally the pupils of both eyes constrict. - Direct light reflex: The constriction of pupils upon which light is shown is called direct light reflex. - Indirect or consensual: The constriction of pupil on the other eye even though no light is shown
  28. 28. Pathways of direct and indirect light reflexes (v.imp.) 29
  29. 29. Pupillary light reflex Direct Consensual
  30. 30. Accommodation
  31. 31. ACCCOMODATION REFLEX • When the eyes are focussed from a distant to near object, three reactions take place • 1. Constriction of pupils • 2. thickening of lens due to contraction of ciliary muscles • 3. Convergence of both eye balls These three reactions together constitute Accommodation or near reflex
  32. 32. Accommodation reflex
  33. 33. LESIONS OF THE VISUAL PATHWAY
  34. 34. Optic nerve lesions (A,B) Causes : Optic atrophy, traumatic avulsion, acute optic neuritis etc. 1.Distal optic nerve lesion (A) • Complete blindness of affected side • Abolition of direct light reflex on affected side • Accommodation reflex intact
  35. 35. 2. Proximal optic nerve lesion (B) • Blindness on affected side • Contralateral hemianopia • Abolition of direct light reflex on affected side • Accommodation reflex intact
  36. 36. Chiasmal lesions (C,D) 1.Central chiasmal lesion (C) • Bitemporal hemianopia • Bitemporal hemianopic paralysis of pupillary reflexes 2.Lateral chiasmal lesion (D) • Binasal hemianopia • Binasal hemianopic paralysis of pupillary reflexes
  37. 37. Causes : I. Intrinsic causes – Lesions which produce thickening of chiasma. Eg. Gliomas, multiple sclerosis II. Extrinsic causes – Compressive lesions. Eg. Pitutary adenoma, meningioma III. Other causes – Include metabolic, toxic and inflammatory syndromes. Eg. Lymphoid hypophysitis, sarcoidosis
  38. 38. Optic tract lesions (E) Causes : I. Intrinsic causes – Demyelinating diseases and infarction. II. Extrinsic causes – Compressive lesions. Eg. Pitutary adenomas, tumours of optic thalamus III. Other causes – syphilitic meningitis, tubercular meningitis
  39. 39. Optic tract lesions • Incongruous homonymous hemianopia • Contralateral hemianopic pupillary responses (Wernicke’s reaction) • Optic disc changes – Descending type of partial optic atrophy is produced characterized by temporal pallor on the side of the lesion and bow tie atrophy on the contralateral side. • Visual acuity is intact
  40. 40. 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.
  41. 41. Lateral geniculate nucleus lesions(E) • Incongruous homonymous hemianopia • Pupillary reflexes are normal as the fibres go to pretectal nucleus and not the LGN • Optic disc pallor may occur due to partial descending atrophy
  42. 42. Lesions of optic radiations (F,G) Common lesions include : • Vascular occlusions • Tumours • Trauma • Temporal lobectomy for seizures
  43. 43. Lesions of optic radiations • Superior quadrantic hemianopia(F) – Pie in the sky lesions. It is explained by the fact that inferior fibres of optic radiations contain fibres from ipsilateral lower temporal retina and contralateral lower nasal retina.(part of optic radiations in temporal lobe) • Inferior quadrantic hemianopia(G) – Pie on the floor lesions. This is the same as above. Difference being the superior fibres are affected. (part of optic radiations in parietal lobe)
  44. 44. • Complete homonymous hemianopia(H) – produced when all fibres of optic radiations are involved sometimes sparing the macular fibres as they lie centrally. • Pupillary reflexes are spared • Optic disc atrophy does not occur
  45. 45. Visual cortex lesions (I,J,K) • Congruous homonymous hemianopia – macular field of vision is spared. It is a feature of occlusion of posterior cerebral artery. • Congruous homonymous macular defects – occurs in lesions at the tip of occipital cortex following head injuries or gun shot injuries
  46. 46. • Bilateral homonymous macular defects – presenting like bilateral central scotoma occur in bilateral lesions of occipital cortex • Pupillary light reflexes are normal • Optic atrophy doesn’t occur. Other manifestations of occipital lobe lesions include : • Cortical blindness • Dyschromatopsia
  47. 47. • Visual hallucinations • Palinopsia – Persistent perception of visual image • Visual anesthesia – transposition of visual stimulus from one hemifield to another • Polyopsia – multiple images of single object which do not disappear on closing the eye.

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