1. ANATOMY OF
VISUAL PATHWAY,FIELD
DEFECTS
AND
ITS LESIONS.
By-Dr. Ruchi
Pherwani

2. Visual field
 Each eye sees a part of the visual
space that defines its visual field.
 The visual fields of both eyes overlap
extensively to create a binocular visual
field. The total visual field is the sum
of the right and left hemifields and
consists of a binocular zone and two
monocular zones.

3. Visual Pathway
 Each eyeball act
as camera ;it
perceives the
images & relay
the sensations to
the
brain(occipital
cortex) via the
VISUAL PATHWAY.

4. VISUAL PATHWAY
 Vision is produced by photoreceptors in the
retina, a layer of cells behind the eye. The
information leaves the eye by manner of the
optic nerve, and there is partly crossing of
axons at the optic chiasm.
 Afterward the chiasm, the axons are termed
as the optic tract. The optic tract wraps
about the midbrain to acquire to the lateral
geniculate nucleus (LGN), where all axons
should synapse.
 From there, the LGN axons fan out via the
deep white matter of the brain as the optic
radiations, that will ultimately travel to
primary visual cortex, at behind the brain.

5.  VISUAL
PATHWAY
comprises of:
Optic Nerve
Optic Chiasma
Optic Tract
Lateral
Geniculate
Body
Optic
Radiations
Visual cortex

6. OPTIC NERVE
 2nd cranial nerve.
 47-50 mm in length.
 Starts from optic disc & extends upto optic chiasma
where the two nerves meet.
 Backward continuation of nerve fibre layer of retina
which consist of axons originating from ganglion
cells.
 Contains the afferent fibres of light reflex
 Has 4 parts : 1)intraocular (1mm)
2)intraorbital (30mm)
3)intra canalicular (6-9mm)
4)intracranial (10mm)

7. Morphologicaly & Embryologicaly optic
nerve is compared to sensory tract of
Brain(white matter) :
 Optic nerve is an
outgrowth of brain.
 Not covered by
neurilemma so does
not regenerate when
cut.
 Fibres of optic nerve
are very thin(2-10
um in diameter)& are
million in number.
 surrounded by
meninges unlike
other peripheral
nerves.
 Both primary &
secondary neurons

8. 1)Intra ocular Part :
 About 1mm in size, passes through sclera ,
choroid & finally appears in eye as optic
disc.
 Divided in 4 portions from anterior to
posterior :a)surface nerve fibre layer.
b) prelaminar region.
c) lamina cribrosa.
d) retrolaminar region.

9. 2) Intraorbital part :
 Extends from back of eyeball
to optic foramina.
 This part slightly sinuous to
give play for the eye
movements.
 Here optic nerve is
surrounded by all 3 layers of
meninges & subarachnoid
space.
 The central retinal artery
along with enters the
subarachnoid space to enter
the nerve on its inferomedial
aspect.
 Near optic foramina,optic
nerve is closely surronded by
annulus of zinn & the origin
of four recti muscles.
 Some fibres of superior &
medial rectus are adherent to

10. 3) Intracanalicular Part
 This part is closely
related to ophthalmic
artery.
 it crosses the nerve
from medial to lateral
side in dural sheath.
 Sphenoid &
posterior ethmoidal
sinuses lie medial to
it & seperated by thin
bony lamina, this
relation accounts for
retrobulbar neuritis
following infection of
sinuses.

11. 4) Intracranial part
 About 10mm
 Lies above cavernous sinus & converges
with its fellow to form chiasma.
 Ensheathed in pia mater.
 Internal carotid artery runs below then
lateral to it.

12. OPTIC CHIASMA
 Flattened structure,12 mm
horizontally & 8mm
anteroposteriorly.
 Ensheathed by pia &
surrounded by CSF.
 Lies over diaphragma sellae so
visual field defects seen in
patient with pituitary tumor
having suprasellar extension.
 Posteriorly chiasma continous
with the optic tracts & form the
anterior wall of 3rd ventricle.
 Nerve fibres arising from nasal
half of two retina decussate at
the chiasma.

13. Anatomical variation in position
of normal optic chiasma:
 a)central : lies directly
over sella, expanding
pituitary tumor
involves chiasma first.
b)pre-fixed : lies more
anteriorly over
tuberculum
sellae,pituitary tumor
involves optic tract
first.
c) post-fixed : lies
more posterior over
dorsum
sellae,pituitary tumor

14. Relations of chiasma :
 Anterior - anterior cerebral
arteries & its
communicating arteries.
 Posterior- tuber cinereum,
infundibulum ,pitutary
body ,posterior perforated
substance.
 Superior- third ventricle.
 Inferior- hypophysis
 Lateral- extra cavernous
part of internal carotid
artery& anterior
perforated substance.

15. 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

16. LATERAL GENICULATE
BODY
 Oval structures situated at termination of
the optic tracts.
 Each consist of 6 layers of neurons(grey
matter) alternating with white matter (optic
fibres)
 Fibres of 2nd order neuron coming via optic
tract relay here.

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. VISUAL CORTEX
 Located on the medial aspect of occipital
lobe, in & near calcarine fissure.
Visual cortex
Visuopsychic
area
Peristriate
area 18
Parastriate
area 19
Visuosensory
area
Striate area
17

19. Modified nomenclature
recognizing five visual areas :

20. Blood supply of Visual
Pathway
Arterial
Circle of
Willis
Carotid
arterial
system
Vertebral
arterial
system

21. Circle of Willis :

22. Blood supply of Optic Nerve:
 A. Intraocular part
• Peripapillary choroidal vessels
Prelaminar
• Posterior choroidal vessels
Lamina
cribrosa
region
• Centrifugal branches from central
retinal artery
• Centripetal branches from pial vessels
Retrolaminar

23. B . Intraorbital part :
• Derived from 6 branches of
internal carotid artery:
ophthalmic, long & short
posterior ciliary artery.
• Lacrimal artery.
• Central artery of retina.
Periaxial
system of
vessels
• Intraneural b/o central retinal
artery.
• Central collateral b/o central
retinal artery.
• Central artery of optic nerve.
Axial
system of
vessels

24. C .Intracanalicular part :
periaxial system of vessels.
D . Intracranial part :
Pial system of vessels
B/o internal
carotid artery
B/o anterior
cerebral artery
B/o ophthalmic
artery
Twigs from
anterior
communicating
artery

25. Venous drainage :
Optic nerve
head
• Central
retinal vein
Orbital part
• Peripheral
pial plexus
• Central
retinal vein
Intracranial
part
• Pial plexus
which ends
in anterior
cerebral &
basal vein

26. Blood supply of Optic
Chiasma
Arterial :
Venous:
• B/o anterior cerebral & anterior
communicating arterySuperior
aspect
• B/o internal carotid artery ,posterior
communicating artery ,anterior superior
hypophyseal artery
Inferior
aspect
• Superior chiasmal vein drains
into anterior cerebral veinSuperior
aspect
• Pre-infundibular vein draining
into basilar vein.Inferior
aspect

27. Blood supply of optic tract:
 Arterial: Pial plexus receiving
contribution from posterior
communicating artery, anterior
choroidal artery & middle cerebral
artery.
 Venous drainage: anterior cerebral
vein & basal vein.

28. Blood supply of lateral geniculate
body:
Posterior
cerebral artery
• Supply fibres coming from superior
homonymous quadrant of retina.
Anterior
choroidal artery
• Supply fibres coming from inferior
homonymous quadrant of retina.
Macular fibres
over region of
hilum
• Supplied by anastomosis from posterior
cerebral & anterior choroidal artery.

29. Blood supply of Optic
radiations
• Anterior choroidal arteryAnterior
part
• Deep optic artery b/o middle
cerebral artery.
Middle
part
• Calcarine branches from
posterior cerebral artery.
Posterior
part

30. Blood supply of visual cortex
Visual cortex
Calcarine artery b/o
Posterior cerebral
artery
Terminal b/o middle
cerebral artery &
anastomosis between
middle& posterior
cerebral artery.

31.  Venous drainage of visual cortex
• Internal cerebral vein
drains in great
cerebral vein of galen
& straight sinus
Medial aspect
• Inferior cerebral vein
drains in cavernous
sinus.Superolateral
aspect

32. LESIONS OF VISUAL
PATHWAY

33. 1) LESIONS OF OPTIC NERVE :
Causes:
optic atrophy
 indirect optic neuropathy
acute optic neuritis
traumatic avulsion of optic nerve.
Characterised by: complete blindness in
affected eye with loss of both direct on
ipsilateral & concensual light reflex on
contralateral side. Near reflex is
preserved.
Eg. Right optic nerve
involvement

34. 2)Lesions through proximal part of
optic nerve :
 ipsilateral blindness.
 contralateral hemianopia
 abolition of direct light reflex on
affected side & concensual light reflex on
contralateral side.
 near reflex intact.

Eg. Rt optic nerve
Involvement in
Proximal part

35. 3)Central lesions of chiasma (sagittal)
causes:
 suprasellar aneurysm
 tumors of pituitary gland
 craniopharyngioma
 suprasellar meningioma & glioma of 3rd
ventricle.
 third ventricular dilatation due to obstructive
hydrocephalus.
 chronic chiasmal arachnoiditis.
 Characterised by:
 Bitemporal hemianopia
 Bitemporal hemianopic
paralysis of pupillary reflex. (usually lead to
partial descending optic atrophy)

36. 4)Lateral chiasmal lesions :
causes:
• Distension of 3rd ventricle causing pressure
on each side of optic chiasma
• Atheroma of carotids & posterior
communicating artery.
Characterised by
• Binasal hemianopia
• Binasal hemianopic
parallysis of pupillary reflex (usually lead to
partial descending optic atrophy)

37. 5)Lesions of optic tract :
Causes:
 Syphilitic meningitis/ gumma.
 Tuberculosis
 Tumors of optic thalamus
 Aneurysm of superior cerebellar or posterior
cerebral arteries.
Characterised by :
• Incongruous homonymous hemianopia with
C/L hemianopic pupillary reaction( wernicke’s
reaction)
• These lesions usually lead to partial
descending optic atrophy & may be associated
with C/L 3rd nerve paralysis & ipsilateral
hemiplegia.

38. 6)Lesions of lateral geniculate body :
 leads to homonymous hemianopia
with sparing of pupillary
reflexes & may end in
partial optic atrophy.

39. 7)Lesions of optic radiations :
Causes:
 Vascular occlusion
 Primary & secondary tumors
 Trauma
 Characterised by :
TOTAL OPTIC
RADIATION
INVOLVEMENT
COMPLETE
HOMONYMOUS
HEMIANOPIA(
sometimes sparing
macula)

40. LESIONS OF
PARIETAL LOBE
(involving
superior fibres of
optic radiations)
INFERIOR
QUADRANTIC
HEMIANOPIA(
PIE ON THE
FLOOR)
LESIONS OF
TEMPORAL
LOBE (involving
inferior fibres of
optic radiations)
SUPERIOR
QUADRANTIC
HEMIANOPIA(
PIE ON THE
ROOF)

41.  Pupillary reactions are normal as
fibres of light reflex leave the optic
tracts to synapse in the superior
colliculi.
 Lesions of optic radiations do not
produce optic atrophy as the 1st order
neurons (optic nerve fibres) synapse
in LGB.

42. 8)Lesions of visual cortex : pupillary
light reflex is normal & optic atrophy does
not occur following visual cortex lesions.
Congruous
homonymous
hemianopia(sparing
macula)
Occlusion of
posterior cerebral
artery supplyin
anterior part of
occipiatl cortex
Congruous
homonymous
macular defect
Head injury/gun
shot injury leading
to lesions of tip of
occipital cortex+

43. Thank you…