Visual Pathway

1. Visual Pathway
Med 6573: Nervous System
University of Minnesota Medical School Duluth
Donna J. Forbes, Ph.D.
29 February 2008

2. 2
• Nolte Chapter 17
• Netter: Plates 86 and 114
• Related materials from other faculty
• Dr. Downing: Histology of the Eye
• Dr. Stauffer: Physiology of the Eye
• Dr. Trachte: Pharmacology of the Eye
• Dr. Hollenhorst: Clinical Ophthalmology
• Dr. Meyerson: Neurological Exam
• Washington University: The Basic Visual Pathway
http://thalamus.wustl.edu/course/basvis.html
Pg. 1
References

3. 3
• Visual Acuity: Eye, CN II & beyond in the visual pathway
• Visual Fields: Central & Peripheral Vision (retina to cortex)
• Ocular Motility: (CN III, IV, VI)
• Reflexes
• Pupillary Light Reflex (CN II & III)
• Accommodation (Near) Reflex
• Corneal Reflex (CN V & VII)
• Retina including Optic disc: (Increased intracranial
pressure; status of blood vessels reflecting hypertension,
diabetes, etc.)
• Visual Pathway: Since it is precisely organized & extends
from the rostral to caudal aspect of the hemispheres, lesions
along the pathway produce specific deficits that can aid in
localizing the lesion.
Pg. 1
Eyes are the window to the brain!
Eye Exam

4. Learning Objectives
 Relationship of bipolar & ganglion cells to the visual pathway
 Relationship of retinal quadrants to visual field quadrants
 Understanding of monocular vs. binocular visual fields
 Importance of “corresponding points” on the retinae & the “Blind spot”
 Components of the visual pathway; nuclei involved; location of
decussations, etc.
 Representation of the visual field within the structures of the visual
pathway. [Upper vs. lower fields; Nasal vs.Temporal fields; Macular vs.
Peripheral fields representation]
 Visual field deficits associated with damage along the visual pathway
 Components & basis of the:
Direct & consensual pupillary light reflex
Pupillary dilation
Accommodation or near reflex
 Definition or description of terms: amblyopia, Argyll Robertson pupil,
diplopia, hemianopsia, heteronymous, homonymous, Horner’s syndrome,
Meyer’s loop, quadrantanopsia, retinotopic, scotoma, strabismus
Pg. 1

5. 5
Pathway extends from the
‘front’ to the ‘back’ of the
brain.
• Precise retinotopic
organization
• Deficits due to lesions of
the pathway give valuable
localizing information.
The Visual Pathway
Pg. 2
OT
ON
OC
VISUAL
CORTEX
RETINA
VISUAL
FIELD
LGN
OPTIC
RADIATIONS
ON = Optic Nerve
OC = Optic Chiasm
OT = Optic Tract
LGN = Lateral Geniculate Nucleus of Thalamus

6. 6
Beginning of the Pathway
Pg. 2

7. 7
Cells
of the
Retina
Pg. 2
Rods and Cones
(Receptors)
Ganglion cells axons form the optic nerve
Bipolar cells

8. 8
Object to be seen
Peripheral Retina
The next slide looks
at the retina as if you
are looking through
the patient’s pupil via
your
ophthalmoscope.
Central Retina (fovea
in the macula lutea)
Pg. 2

9. 9
Retinal Quadrants
nose
UTQ UTQ
LTQ LTQ
LNQ
LNQ
UNQ UNQ
Right retina Left retina
Papilla (optic
nerve head)
Macula with
fovea centralis
Retina as you would see it through the
ophthalmoscope & the patient’s pupil
Temporal Hemiretina
UTQ = upper temporal quadrant
LTQ = lower temporal quadrant
Nasal Hemiretina
UNQ = upper nasal quadrant
LNQ = lower nasal quadrant
Horizontal Meridian
Vertical Meridian
Pg. 2
The blind spot in the Visual Field corresponds to the location of
the optic nerve head on the NASAL side of the retina.

10. 10
Visual Fields & the Visual Pathway
Pg. 2
OT
ON
OC
VISUAL
CORTEX
RETINA
VISUAL
FIELD
LGN
OPTIC
RADIATIONS
ON = Optic Nerve
OC = Optic Chiasm
OT = Optic Tract
LGN = Lateral Geniculate Nucleus of Thalamus
The following slides
begin with the
visual fields and
then follow the
pathway from the
retina to the visual
cortex.

11. 11
Definition: The entire area that
can be “seen” by the patient
without movement of the head and
with the eyes fixed on a single
spot.
Visual Fields Pg. 3
Mapping of Visual Fields:
• Confrontational method
(see Dr. Meyerson’s
“Neurological Exam” notes)
• Perimetry (Manual or
Automated)
Temporal Field of
Left Eye
Nasal Field of
Left Eye
F
Normal Monocular Visual
Field of Right Eye
Normal Monocular Visual
Field of Left Eye
F
Monocular Visual Fields
Monocular Visual Fields:
• Each eye is tested separately.
• The monocular visual field is plotted with the Fovea (F) at the center.
• The monocular visual field (colored area -- blue for left; green for right in this example) is
not round.
• Horizontal and Vertical Meridians correspond to those of the retina and divide the visual
field into upper temporal, upper nasal, lower temporal and lower nasal quadrants.
• Imagine that this is your visual field, i.e. all that you can see with your left eye and your right
eye (tested separately) when you look straight ahead and do not move your head or eyes.
Vertical
Meridian
Horizontal
Meridian
Upper
Field
of
Left
Eye
Lower
Field
of
Left
Eye
UTQ
LTQ
UNQ
LNQ

12. 12
Blind Spot
• 15° to the temporal side
of the visual field of each
eye
• On the horizontal
meridian
• Corresponds to the
location of the optic
nerve head 15° to the
nasal side of the retina of
each eye.
Visual Fields
Demonstration of the Blind Spot:
• Draw the star and box on a piece of paper.
• Close your left eye; Look at the star with your right eye; Move paper back and forth
until the green box disappears.
• Open your left eye and the box can be seen because even though it was falling on the
blind spot of the right eye, it is not falling on the blind spot of your left eye.
• With both eyes open & binocular vision intact, you don’t realize that there is a blind
spot since the corresponding spot on the contralateral retina will see the object.
Pg. 3
Temporal Field of
Left Eye
Nasal Field of
Left Eye
Normal Monocular Visual
Field of Left Eye
F F
Normal Monocular Visual
Field of Right Eye
Upper
Field
of
Left
Eye
Lower
Field
of
Left
Eye

13. 13
Visual Fields:
Binocular
Pg. 3
Normal Binocular Visual Field
F
Right Visual Field
Left Visual Field
Upper Fields
Lower Fields
Temporal Field of
Left Eye
Nasal Field of
Left Eye
Normal Monocular Visual
Field of Left Eye
F F
Normal Monocular Visual
Field of Right Eye
Understand the difference between the “monocular visual field of the left eye” vs.
the “binocular left visual field” and vice versa for the right counterparts.
• Binocular field combines the two monocular
visual fields with the foveas (F) aligned with
one another. (i.e. the ‘pink area’ in the image
to the right)
• Left Visual Field seen by both the left & right
eyes.
• Right Visual Field seen by both the left &
right eyes.
• Monocular crescent for each eye (blue for
left eye & green for right eye) is only seen by
the nasal retina of the same eye.
Monocular
Crescent of
Right Eye
Monocular
Crescent of
Left Eye

14. 14
Visual Fields:
Binocular
Binocular vision is dependent upon the
extraocular muscles aligning the eyes so
that an image falls on “corresponding
points” on the retina of each eye. This is
essential for the brain to perceive a single
image. Diplopia occurs when the images
are not aligned to fall on corresponding
points of each retina.
Pg. 3
Normal Binocular Visual Field
F
Right Visual Field
Left Visual Field
Upper Fields
Lower Fields
Temporal Field of
Left Eye
Nasal Field of
Left Eye
Normal Monocular Visual
Field of Left Eye
F F
Normal Monocular Visual
Field of Right Eye
Demonstration of the Binocular
Visual Field & Monocular Crescent:
• Look straight ahead
• Close your right eye
• Move your finger to the right
until it disappears
• Open right eye to see the pencil
-- in the right temporal
monocular crescent of your
visual field.

15. 15
Visual Fields Pg. 4
The image of an object in the visual field is inverted and reversed right to left on the retina.
• Temporal field of left eye (red & purple) is seen by the nasal retina of the left eye
• Nasal field of the left eye (green & yellow) is seen by the temporal retina of the left eye.
• Superior field of the left eye (red & green) is seen by the inferior retina of the left eye.
• Inferior field of the left eye (purple & yellow) is seen by the superior retina of the left eye.
• Similarly, the image is inverted & reversed for the right eye.
Retina of
Left Eye
Retina of
Right Eye
NOTE:
DOTTED OUTLINE = MONOCULAR
FIELD OF LEFT EYE
SOLID OUTLINE = MONOCULAR FIELD
OF RIGHT EYE
Binocular
Visual Field
Monocular
Crescent of
Right Eye
Monocular
Crescent of
Left Eye
Note: To avoid confusion and abide by convention, central representation, visual
deficits, etc. will be described in terms of visual fields and not retinal quadrants.

16. 16
Visual Pathway
• Optic Nerve (ON)
• = Axons of ganglion cells in the retina
of the corresponding eye
• Outgrowth of diencephalon, so is a
CNS tract & not a ‘true’ cranial nerve.
• Myelinated by oligodendrocytes.
• Optic Chiasm (OC)
• Located just anterior to pituitary
• Partial crossing of optic nerve axons
in the OC is essential to binocular
vision
• Axons from temporal fields cross
• Axons from nasal fields do not
cross
• “Wilbrand’s knee” may be artifact
Note: Reference point = Visual Fields
Pgs. 4 - 5
Retinotopic representation
• Central (macular) vision
• Peripheral vision
Left visual field Right visual field
Right retina
Left retina
Left LGN
Tempora
l
Nasal Tempora
l
Nasal
lateral lateral
medial medial
LVF
LVF UVF
UVF
E.W.
Right visual
cortex
midbrain
Right LGN
Left visual cortex
Left
temporal
retina
Right
temporal
retina
Nasal
retina
Ciliary
ganglion
pretectal
nuclei
cuneus
lingual
gyrus
Calcarin
e sulcus
III
III
Upper field
Lower field
VISUAL FIELDS:
Hatched = binocular
Stippled = monocular
Central area = macula
ON
OC
OT

17. 17
• Optic Tract (OT)
• Optic nerve fibers from the optic chiasm
continue as the optic tract & terminate in
the lateral geniculate nucleus of thalamus.
• Each tract contains axons that carry input
from the contralateral visual field.
• Left OT receives from R. visual field
• Right OT receives from the L. visual
field
Pgs. 4 - 5
Note: Reference point = Visual Fields
Retinotopic representation
• Central (macular) vision
• Peripheral vision
Left visual field Right visual field
Right retina
Left retina
Left LGN
Tempora
l
Nasal Tempora
l
Nasal
lateral lateral
medial medial
LVF
LVF UVF
UVF
E.W.
Right visual
cortex
midbrain
Right LGN
Left visual cortex
Left
temporal
retina
Right
temporal
retina
Nasal
retina
Ciliary
ganglion
pretectal
nuclei
cuneus
lingual
gyrus
III
III
Visual Pathway
Post-Chiasmatic portion of the pathway:
From optic tract to visual cortex, each side of the brain
deals with the contralateral visual field.
Upper field
Lower field
VISUAL FIELDS:
Hatched = binocular
Stippled = monocular
Central area = macula
ON
OC
OT
• Lateral Geniculate Nucleus (LGN)
• Primary termination of OT fibers
• Each LGN receives input from the
contralateral visual field.
• OT Projections to pretectum for reflexes

18. 18
Retinotopic representation
• Central (macular) vision
• Peripheral vision
• Geniculocalcarine Tract (= optic
radiations)
• Axons of LGN neurons travel to primary
visual cortex (Area 17) via the
geniculocalcarine tract located in the
retrolenticular and sublenticular portions
of the internal capsule.
• Axons from upper visual fields take a
looping course into the temporal lobe on
the way to visual cortex. (=Meyer’s loop)
• Axons from lower visual fields take a
more direct route to visual cortex.
• Macular fibers are in an intermediate
location in the optic radiation.
Pgs. 4 - 5
Note: Reference point = Visual Fields
Left visual field Right visual field
Right retina
Left retina
Left LGN
Tempora
l
Nasal Tempora
l
Nasal
lateral lateral
medial medial
LVF
LVF UVF
UVF
E.W.
Right visual
cortex
midbrain
Right LGN
Left visual cortex
Left
temporal
retina
Right
temporal
retina
Nasal
retina
Ciliary
ganglion
pretectal
nuclei
cuneus
lingual
gyrus
Calcarin
e sulcus
III
III
Meyer’s
loop
Optic radiation or
geniculocalcarine
tract
Visual Pathway
Post-Chiasmatic portion of the pathway:
From optic tract to visual cortex, each side of the brain
deals with the contralateral visual field.
Upper field
Lower field
VISUAL FIELDS:
Hatched = binocular
Stippled = monocular
Central area = macula
ON
OC
OT

19. 19
Visual Pathway
Pgs. 4 - 5
Note: Reference point = Visual Fields
Retinotopic representation
• Central (macular) vision
• Peripheral vision
Left visual field Right visual field
Right retina
Left retina
Left LGN
Tempora
l
Nasal Tempora
l
Nasal
lateral lateral
medial medial
LVF
LVF UVF
UVF
E.W.
Right visual
cortex
midbrain
Right LGN
Left visual cortex
Left
temporal
retina
Right
temporal
retina
Nasal
retina
Ciliary
ganglion
pretectal
nuclei
cuneus
lingual
gyrus
Calcarin
e sulcus
III
III
Meyer’s
loop
Optic radiation or
geniculocalcarine
tract
Upper field
Lower field
VISUAL FIELDS:
Hatched = binocular
Stippled = monocular
Central area = macula
ON
OC
OT
• Primary Visual Cortex (Area 17)
• Located on either side of & within the
calcarine fissure.
• Upper fields project to the lingual gyrus.
• Lower fields project to the cuneus.
• Macular representation is most caudal in Area
17.
• Peripheral field representation is in the rostral
2/3rds of Area 17.
• Lesions of Area 17 result in blindness in the
contralateral visual field.
• Association Visual Cortex (Areas 18
& 19)
• Input from Area 17 & elsewhere
• Deals with complex aspects of vision
• Lesions of result in visual agnosia.

20. 20
Lesions of the Visual Pathway
1. Normal visual fields
2. Blindness of the right eye
3. Blindness of right eye + contralateral left upper
quadrantanopia
4. Bitemporal heteronymous hemianopsia
5. Left homonymous hemianopsia
6. Left upper homonymous quadrantanopsia
7. Left homonymous hemianopsia with macular
sparing
Right
Left
Definitions
Strabismus
Diplopia
Amblyopia
Scotoma
Quadrantanopsia - # 3, 6
Hemianopsia - # 4, 5, 7
Heteronymous Defects - # 3, 4
Homonymous Defects - # 5, 6, 7
Congruous Defects - # 5, 6, 7
Incongruous Defects - # 3
Altitudinal Defects - # 6
Masked area = area
of visual loss
Pg. 6
Aka
“field
cuts”
Fields, not
retinal
quadrants

21. 21
Lesions of the Visual Pathway
1. Normal visual fields
2. Blindness of the right eye
3. Blindness of right eye + contralateral left upper
quadrantanopia
4. Bitemporal heteronymous hemianopsia
5. Left homonymous hemianopsia
6. Left upper homonymous quadrantanopsia
7. Left homonymous hemianopsia with macular
sparing
Right
Left
Pg. 6

22. 22
Right Left
Pupillary Constriction
(Miosis)
Nolte 17-38
Afferent limb =
Optic Nerve (SSA)
Efferent limb = Oculomotor Nerve (GVE)
Postganglionic
Preganglionic
Direct
Reflex
Consensual
Reflex
Pg. 7
AKA Pupillary Light
Reflex

23. 23
Right Left
B
C
Right Left
Right Left
Nolte 17-38
Reflex abolished if afferent or efferent is damaged.
Pg. 7
Afferent
defect
Efferent
defect

24. 24
Pupillary Dilation
(Mydriasis)
Decreased light to pupil
Severe pain
Strong emotional stimulus
Reticular
Formation
Reticulospinal
fibers
Preganglionic
Sympathetic Neurons
in Thoracic Cord (T1-
T2)
(pre-ganglionic
sympathetic)
Dilation
of pupil
Superior
Cervical
Ganglion
(post-ganglionic
sympathetic)
Cortex,
Thalamus &
Hippocampus
? Hypothalamus
(CNS control center
for AN S)
?
Horner’s Syndrome
• Pupillary Constriction
• Ptosis
• Flushed & Dry Skin
• Loss of Sympathetics
• Lesion can be in CNS or PNS
• Deficits ipsilateral to lesion
Pg. 7-8

25. 25
Accommodation (or “Near”) Reflex
1. Initiated by shift in gaze from far to near.
3. Efferent limb: GSE & GVE of Oculomotor
Optic nerve  Optic tract  Lateral Geniculate Nucleus  Optic Radiation
 Primary Visual Cortex  Association Visual Cortex  Optic Radiation 
Br. of Superior Colliculus  Superior Colliculus  Oculomotor Nuclei 
Oculomotor Nerve
Argyll Robertson pupil: Pupillary constriction occurs as part of the
accommodation reflex, but not in response to light.
2. Three components:
Ocular convergence
Pupillary constriction
Lens thickening
4. Afferent limb & Central Connections:
Pg. 8

26. 26
See Visual Pathway
Practice Quiz

27. 27