Visual Pathway
Med 6573: Nervous System
University of Minnesota Medical School Duluth
Donna J. Forbes, Ph.D.
29 February 2008
Pg. 1
References
• 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
2
Eye Exam
Pg. 1
Eyes are the window to the brain!
• 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 3
localizing the lesion.
Learning Objectives









Pg. 1
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. 2
The Visual Pathway
VISUAL
FIELD
RETINA
ON
OT
LGN
OC
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.
OPTIC
RADIATIONS
ON = Optic Nerve
OC = Optic Chiasm
OT = Optic Tract
LGN = Lateral Geniculate Nucleus of Thalamus
VISUAL
CORTEX
5
Beginning of the Pathway
Pg. 2
6
Pg. 2
Ganglion cells
axons form the optic nerve
Bipolar cells
Rods and Cones
(Receptors)
Cells
of the
Retina
7
Pg. 2
Object to be seen
The next slide looks
at the retina as if you
are looking through
the patient’s pupil via
your
ophthalmoscope.
Peripheral Retina
Central Retina (fovea
in the macula lutea)
8
Pg. 2
Retinal Quadrants
Left retina
Right retina
Vertical Meridian
UTQ
UNQ
LTQ
LNQ
UNQ
UTQ
LNQ
LTQ
nose
Macula with
fovea centralis
Horizontal Meridian
Papilla (optic
nerve head)
Retina as you would see it through the
ophthalmoscope & the patient’s pupil
Temporal Hemiretina
Nasal Hemiretina
UTQ = upper temporal quadrant
UNQ = upper nasal quadrant
LTQ = lower temporal quadrant
LNQ = lower nasal quadrant
The blind spot in the Visual Field corresponds to the location of
the optic nerve head on the NASAL side of the retina.
9
Pg. 2
Visual Fields & the Visual Pathway
VISUAL
FIELD
RETINA
ON
OT
OC
The following slides
begin with the
visual fields and
then follow the
pathway from the
retina to the visual
cortex.
LGN
OPTIC
RADIATIONS
ON = Optic Nerve
OC = Optic Chiasm
OT = Optic Tract
LGN = Lateral Geniculate Nucleus of Thalamus
VISUAL
CORTEX
10
Visual Fields
Pg. 3
Monocular Visual Fields
Definition: The entire area that
• Confrontational method
(see Dr. Meyerson’s
“Neurological Exam” notes)
• Perimetry (Manual or
Automated)
Monocular Visual Fields:
Nasal Field of
Left Eye
Vertical Horizontal
Meridian Meridian
UTQ
UNQ
F
Lower Field of
Left Eye
Mapping of Visual Fields:
Upper Field of
Left Eye
can be “seen” by the patient
without movement of the head and
with the eyes fixed on a single
spot.
Temporal Field of
Left Eye
LTQ
F
LNQ
Normal Monocular Visual
Field of Left Eye
Normal Monocular Visual
Field of Right Eye
• 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.
11
Visual Fields
Pg. 3
Blind Spot
Temporal Field of
Left Eye
F
F
Normal Monocular Visual
Field of Left Eye
Normal Monocular Visual
Field of Right Eye
Lower Field of
Left Eye
• On the horizontal
meridian
Upper Field of
Left Eye
• 15° to the temporal side
of the visual field of each
eye
Nasal Field of
Left Eye
• Corresponds to the
location of the optic
nerve head 15° to the
nasal side of the retina of
each eye.
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. 12
Visual Fields:
Binocular
Temporal Field of
Left Eye
Pg. 3
Nasal Field of
Left Eye
F
F
• Binocular field combines the two monocular
visual fields with the foveas (F) aligned withNormal Monocular Visual
one another. (i.e. the ‘pink area’ in the image Field of Left Eye
Left Visual Field
to the right)
Normal Monocular Visual
Field of Right Eye
Right Visual Field
• Left Visual Field seen by both the left & right
eyes.
• Right Visual Field seen by both the left &
right eyes.
Monocular
Crescent of
Left Eye
Upper Fields
F
• 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
Lower Fields
Normal Binocular Visual Field
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.
13
Visual Fields:
Binocular
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.
Temporal Field of
Left Eye
Pg. 3
Nasal Field of
Left Eye
F
F
Normal Monocular Visual
Field of Left Eye
Normal Monocular Visual
Field of Right Eye
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.
Left Visual Field
Right Visual Field
Upper Fields
F
Lower Fields
Normal Binocular Visual Field
14
Visual Fields
Monocular
Crescent of
Left Eye
Binocular
Pg. 4
Monocular
Crescent of
Right Eye
NOTE:
Visual Field
DOTTED OUTLINE = MONOCULAR
FIELD OF LEFT EYE
Retina of
Left Eye
Retina of
Right Eye
SOLID OUTLINE = MONOCULAR FIELD
OF RIGHT EYE
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.
Note: To avoid confusion and abide by convention, central representation, visual
15
deficits, etc. will be described in terms of visual fields and not retinal quadrants.
Visual Pathway
Left visual field
Pgs. 4 - 5
Right visual field
VISUAL FIELDS:
Upper field
• Optic Nerve (ON)
Hatched = binocular
Stippled = monocular
Lower field
• = Axons of ganglion cells in the retina
of the corresponding eye
Central area = macula
• Outgrowth of diencephalon, so is a
CNS tract & not a ‘true’ cranial nerve.
• Myelinated by oligodendrocytes.
Right retina
Left retina
• Optic Chiasm (OC)
• Located just anterior to pituitary
• Partial crossing of optic nerve axons
in the OC is essential to binocular
vision
Tempora Nasal
l
Nasal Tempora
l
Ciliary
ganglion
Right LGN
Left LGN
OT
UVF
lateral
LVF
medial
• Axons from nasal fields do not
cross
• “Wilbrand’s knee” may be artifact
Note: Reference point = Visual Fields
Right
temporal
retina
III
OC
• Axons from temporal fields cross
Retinotopic representation
• Central (macular) vision
• Peripheral vision
Nasal
ON
retina
Left
temporal
retina
LVF
midbrain
UVF
medial
III
lateral
E.W.
pretectal
nuclei
cuneus
lingual
gyrus
16
Left visual cortex
Right visual
cortex
Calcarin
e sulcus
Visual Pathway
Left visual field
Post-Chiasmatic portion of the pathway:
Upper field
From optic tract to visual cortex, each side of the brain
deals with the contralateral visual field.
Lower field
Pgs. 4 - 5
Right visual field
VISUAL FIELDS:
Hatched = binocular
Stippled = monocular
Central area = macula
• Optic Tract (OT)
• Optic nerve fibers from the optic chiasm
continue as the optic tract & terminate in
the lateral geniculate nucleus of thalamus.
Right retina
Left retina
• Each tract contains axons that carry input
from the contralateral visual field.
• Left OT receives from R. visual field
Tempora Nasal
l
Nasal
ON
retina
Left
temporal
retina
• Right OT receives from the L. visual
field
III
OC
Nasal Tempora
l
Ciliary
ganglion
Right LGN
Left LGN
• Lateral Geniculate Nucleus (LGN)
• Primary termination of OT fibers
Right
temporal
retina
OT
UVF
lateral
LVF
medial
LVF
midbrain
UVF
medial
III
lateral
E.W.
• Each LGN receives input from the
contralateral visual field.
pretectal
nuclei
• OT Projections to pretectum for reflexes
Retinotopic representation
• Central (macular) vision
• Peripheral vision
Note: Reference point = Visual Fields
cuneus
lingual
gyrus
17
Left visual cortex
Right visual
cortex
Visual Pathway
Left visual field
Post-Chiasmatic portion of the pathway:
Pgs. 4 - 5
Right visual field
VISUAL FIELDS:
Upper field
Hatched = binocular
From optic tract to visual cortex, each side of the brain
deals with the contralateral visual field.
Stippled = monocular
Lower field
Central area = macula
• 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.
Right retina
Left retina
Tempora Nasal
l
Note: Reference point = Visual Fields
Right
temporal
retina
III
OC
Nasal Tempora
l
Ciliary
ganglion
Right LGN
Left LGN
OT
UVF
lateral
LVF
medial
• Macular fibers are in an intermediate
location in the optic radiation.
Retinotopic representation
• Central (macular) vision
• Peripheral vision
Nasal
ON
retina
Left
temporal
retina
LVF
midbrain
UVF
medial
III
E.W.
pretectal
nuclei
lateral
Meyer’s
loop
Optic radiation or
geniculocalcarine
tract
cuneus
lingual
gyrus
18
Left visual cortex
Right visual
cortex
Calcarin
e sulcus
Visual Pathway
Left visual field
• Primary Visual Cortex (Area 17)
Pgs. 4 - 5
Right visual field
VISUAL FIELDS:
Upper field
Hatched = binocular
• Located on either side of & within the
calcarine fissure.
Stippled = monocular
Lower field
Central area = macula
• 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.
Tempora Nasal
l
III
Nasal Tempora
l
Ciliary
ganglion
Right LGN
OT
UVF
lateral
LVF
medial
• Deals with complex aspects of vision
LVF
midbrain
UVF
medial
III
E.W.
pretectal
nuclei
• Lesions of result in visual agnosia.
Note: Reference point = Visual Fields
Right
temporal
retina
Left LGN
• Input from Area 17 & elsewhere
Retinotopic representation
• Central (macular) vision
• Peripheral vision
Nasal
ON
retina
Left
temporal
retina
OC
• Association Visual Cortex (Areas 18
& 19)
Right retina
Left retina
lateral
Meyer’s
loop
Optic radiation or
geniculocalcarine
tract
cuneus
lingual
gyrus
19
Left visual cortex
Right visual
cortex
Calcarin
e sulcus
Pg. 6
Lesions of the Visual Pathway
Left
1. Normal visual fields
Right
Fields, not
retinal
quadrants
2. Blindness of the right eye
Definitions
Strabismus
Diplopia
3. Blindness of right eye + contralateral left upper
quadrantanopia
Amblyopia
Scotoma
Quadrantanopsia - # 3, 6
4. Bitemporal heteronymous hemianopsia
Hemianopsia - # 4, 5, 7
5. Left homonymous hemianopsia
Aka
“field
cuts”
Heteronymous Defects - # 3, 4
Homonymous Defects - # 5, 6, 7
6. Left upper homonymous quadrantanopsia
Congruous Defects - # 5, 6, 7
Incongruous Defects - # 3
7. Left homonymous hemianopsia with macular
sparing
Altitudinal Defects - # 6
20
Masked area = area
of visual loss
Pg. 6
Lesions of the Visual Pathway
Left
1. Normal visual fields
Right
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
21
Pg. 7
Pupillary Constriction
Right
Direct
Reflex
Afferent limb =
Optic Nerve (SSA)
(Miosis)
Left
Consensual
Reflex
AKA Pupillary Light
Reflex
Efferent limb = Oculomotor Nerve (GVE)
Postganglionic
Preganglionic
Nolte 17-38
22
Reflex abolished if afferent or efferent is damaged.
Pg. 7
Right
Left
Right
Left
B
Afferent
defect
C
Right
Left
Efferent
defect
23
Nolte 17-38
Pg. 7-8
Pupillary Dilation
(Mydriasis)
Decreased light to pupil
Severe pain
Strong emotional stimulus
?
Cortex,
Thalamus &
Hippocampus
Hypothalamus
(CNS control center
for AN S)
?
Reticular
Formation
Reticulospinal
fibers
Dilation
of pupil
(post-ganglionic
sympathetic)
Superior
Cervical
Ganglion
(pre-ganglionic
sympathetic)
Preganglionic
Sympathetic Neurons
in Thoracic Cord (T1T2)
Horner’s Syndrome
• Pupillary Constriction
• Ptosis
• Flushed & Dry Skin
• Loss of Sympathetics
• Lesion can be in CNS or PNS
• Deficits ipsilateral to lesion
24
Pg. 8
Accommodation (or “Near”) Reflex
1. Initiated by shift in gaze from far to near.
Ocular convergence
2. Three components: Pupillary constriction
Lens thickening
3. Efferent limb: GSE & GVE of Oculomotor
4. Afferent limb & Central Connections:
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.
25
See Visual Pathway
Practice Quiz
26
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
27