6. Optic Nerve
Axoplasmic transport : clearance of expired
organelles, structural maintainance, and energy
requirements.
Interruption of axoplasmic transport : ischemia,
compression, inflammation.
Orthograde axonal transport : away from the cell
body LGN.
Retrograde axonal transport : toward cell body.
9. Intra-orbital Optic Nerve
Myelination (oligodendrocytes).
20-30 mm Long.
Axons: mylein and glial cell (metabolic support
at the nodes of Ranvier).
10. Intracranalicular Optic Nerve
Within the two bases of the LWS.
Medial wall of canal forms lateral wall of
sphenoid sinus (can be absent !).
Within canal : meninges, ophthalmic artery and
sympathetic plexus.
10 mm length.
Tight space !
Internal carotid artery.
11. Intracranial Optic Nerve
Leaves the cranial end of the optic canal
(medially, backwards, upwards).
4-15 m (depending on the position of chiasm).
Upward 45 degree-angle.
Anterior cerebral and anterior comunicating
artery lie superior.
16. Chiasm
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.
25. Band atrophy
From (Practical viewing of the optic disk)
26. Retrochiasmal Visual Pathway
Lesions
Bilateral.
Homonymous.
Complete or incomplete.
Congrous or incongrous.
27. Optic Tract Lesions
Contralateral RAPD (may be an ipsilateral
afferent pupillary defect if a concomitant optic
neuropathy exists)
A specific form of optic atrophy (band atrophy)
due to the involvement of nasal fibers (temporal
field) in the contralateral eye
An incongruous homonymous hemianopsia.
28. Optic Tract
Travel around the cerebral peduncles at dorsal
midbrain.
Divides into lateral root LGN , and a smaller
medial root pretectal area (pupillary light
reflex)
30. Optic tract lesions
Band Atrophy due to compression
Hoyt Wf,
Kommerell G. Der fundus oculi bei homonyermeinaopia.
of the left tract.
Klin Monatsblat Augenheilkd 1973; 162: 456-464)
31. Lateral Geniculate Bodies Lesions
Part of the thalamus.
Hilum, medial and lateral horn.
Six laminae (layers 1-6), crossed fibers1,4,6 ,
uncrossed fibers 2,3,5.
medial
lateral
32. LGB
Upper quadrant medial aspect of LGN,
Lower quadrant lateral aspect of LGN.
Macular fibers central wedge of LGN.
33. LGB
1- Optic nerve
2- Optic chiasma
3- Optic tract
4- Lateral geniculate body
5- Optic radiation
6- Visual cortex
7-Superior colliculus of the
midbrain
8- Putamen
9- Long association bundle -
inferior occipitofrontal
fasciculus
10- Pulvinar of the thalamus
11-Calcarine fissure
12- Posteroinferior horn of
the lateral ventricle
36. Lateral Geniculate Nucleus
Upper quadrant medial aspect of LGN,
Lower quadrant lateral aspect of LGN.
Macular fibers central wedge of LGN.
Layers 1,2: magnocellular. (motion)
Layers 3-6: Parvocellular. (color)
37. LGB lesions
An incongruous wedge defect tending to point
toward fixation (spears to fixation)
Usually complete or nearly complete field
homonymous defect.
39. Optic radiations
Nerve fibers bundles with cell bodies in the
LGN.
Loop of Meyers (around temporal and inferior
horn of LV).
Inferior fascicle.
Superior fascicle.
40. Optic radiations
Inferior fascicle anterior pole of temporal
lobe lower calcarine cortex.
Superior fascicle parietal lobe upper
calacrine cortex.
41. Parietal lesions
“Pie on the floor” homonynous defect.
Associated neurologic signs and symptoms
(e.g., hemiplegia, hemisensory loss, visual, or
neglect) may be present .
42. Anterior temporal lobe
“Pie on the sky” homonymous.
Often incongrous.
Seizures, hemiparesis, hemianesthesia.
Contralateral neglect (Non-dominant).
Aphasia (Dominant).
46. Primary Visual Cortex ( V1)
Upper bank and lower bank (Calcarine fissure).
Inferior visual filed (upper bank) , Superior
visual field (lower bank).
Macular projections represented by 50%-60% of
the area of the calcarine cortex.
Occipital tip is for foveal vision.
47. Occipital cortex lesions
Isolated (i.e., without other neurologic deficit)ز
Congruous.
Paracentral or peripheral.
Complete or incomplete
Macular involvement or macular sparing of the
central 5 degrees may occur (occipital pole
involvement).
51. Visual Association Areas
V2: input from V1.
V3: sends info to basal ganglia and midbrain.
V3a: perceive motion and direction.
V4 : (lingual and fusiform gyrus) color.
V5 : (medial temporal visual region) speed and
direction, origin of pursuit movemen.
V6 : (parietal) represent “extra personal space”.
53. “Where” Pathway
Dorsal stream (occipitoparietal): Spatial
orientation ,visual guidance of movement.
V1 V3 V5Parietal and superotemporal
cortex.
Continuation of magnocellular pathway.
Simultagnosia, optic ataxia, acquired oculomotor
apraxia, and hemispatial neglect.
54. Cortical blindness
Due to bilateral occipital lobe lesions.
Often misdiagnosed as functional vision loss.
Stroke, severe blood loss, Eclampsia,
hypertension, angiography, CO poisoning,
cyclosporine.
55. Dyschromatopsia
Bilateral occipital lobe lesions in the lingual or
fusiform gyri of the medial occipital lobe (medial
occipito-temporal lobe).
Rarely no field defect.
Unilateral involvement may cause
hemidyschromatopsia.
56. Alexia without Agraphia
Loss of ability to read but can write.
Left occipital lobe and splenium of corpus
callosum.
57. Palinopsia
Persistant or recurrence of visual stimulus after
it has been removed.