The document covers the visual pathways in the human brain, detailing the structure and function of the retina, optic nerve, optic chiasm, and visual centers in the occipital cortex. It explains the roles of various brain areas in visual processing, including recognition of objects, motion detection, and coordination of eye movements. Additionally, it addresses optic pathway lesions and their effects on vision, highlighting terms such as anopia and hemianopia.

1. VISUAL PATHWAYS
Dr. K. Ambareesha, PhD
Associate Professor, Department of
Physiology, GMC Jangaon, Telangana

2. SPECIFIC LEARNING OBJECTIVES
Introduction
Layers of Retina
Visual pathway
Order of neurons
Retina
Optic nerve
Optic chaism
Lateral geniculate nucleus
Optic radiation
Visual centres

3. A schematic of the anatomy of the
eye

4. Layers of the Retina

5. Three order of neurons
1st
order neurion •Bipolar cells
2nd
order neuron •Ganglion cells
3rd
order neuron •LGN

6. Visual pathway

7. Retina
Photosensitive layer that
converts light into electrical
impulse

8. Optic Nerve

9. Optic Nerve

10. Optic Chaisma

11. Optic tract
OPTIC
TRACT

12. Lateral Geniculate nucleus (LGN)

13. Optic Radiation
Optic
Radiation

14. Projection of retina on primary
visual cortex
Medial view of the human right cerebral hemisphere showing projection of the retina on the primary
visual cortex in the occipitalcortex around the calcarine fissure.

15. VISUAL CENTRES

16. Visual Cortex
Representation of retina on the medial side of the occipital cortex (area 17)

17. Area 18 : visuaopsychic area (V2)
Representation of area 17, 18 and 19 on the lateral surface of the
occiptal lobe . MT, middle temporal, MST, medial superior temporal
Visual orientation,
depth perception

18. Area 8: Frontal eye field
Located@ Middle
frontal gyrus
It is concerned with
voluntary conjugate
deviation of eye s to
the opposite side

19. Other areas
Areas 20,21,37,7, Middle temporal and medial superior temporal areas also
participate in visual processing
• Role of Area 20, 21, and 37 involved in analysis of visual details:
1. Recognisation of faces, objects and their texure
2. Recognisation of letters
3. Deatiled colour of objects
4. Understanding the imp of objects and colours.
• Middle temporal and medial superior temporal areas and area 7:
• Analysis of 3dimentional position of objects in the space
• Recognisation of their gross form
• Detection of motion of the objects

20. Projections from visual cortex
Some of the main areas to which the primary visual cortex
(V1) projects in the human brain. Lateral and medial views. LO, lateral
occipital; MT, medial temporal; VP, ventral parietal.

21. Functions of visual projection
areas in the human brain.

22. CONNECTIONS OF VISUAL PATHWAY

23. Connections
From
optic
chaisma
to
suprachaismtic
nucleus
of
hypothalamus
and
from
there
to
the
limbic
system
.
•
This
may
be
concerned
with
cirtain
circadian
rhythms
and
sexual
cycles
in
birds
and
some
animals
From
the
occipital
cortex
to
the
frontal
eye
field
(area8).
•
This
is
concerned
with
the
movement
of
the
eye
ball
(convergence)
From
occipital
cortex
to
superior
collicli
and
from
there
to
III,
IV,
VI
cranial
nuclei
and
to
the
spinal
cord.
•
Fibers
also
reach
the
superior
colliculi
form
the
optic
tract.
•
These
mediate
tone,
posture,
equlibrium
and
visuospinal
reflexes.

24. Connections
Fibers from optic
tract before
they end in LGB
reach pretectal
nucleus, which
inturn send
fibers toIII
cranial nerve
nucleus. This
mediates the
light reflex

25. Connections
5
•
Some
fibers
from
the
optic
tract
reach
vestibulocerebellum
through
inferior
olivary
complex.
•
This
is
responsible
for
coardination
of
movements
of
the
eyes
and
head
6
•
Corticogeniculate
fibers
from
the
primary
visual
cortex
and
reticulogeniculate
fibers
from
reticular
formation
of
the
midbrain
are
inhibitory
to
the
LGN.
•
They
influence
response
of
LGN
cells
to
the
impulses
coming
from
Ganglion
cells
7 •
Retinohypothalamic
projections
may
also
influence
sleep
patters

26. Optic pathway lesions
A lesion that interrupts one optic nerve
causes blindness in that eye (A).
 A lesion in one optic tract causes blindness in
half of the visual field (C) and is called homonymous (same
side of both visual fields) hemianopia (half-blindness).
Lesions affecting the optic chiasm destroy
fibers from both nasal hemiretinas and produce a
heteronymous (opposite sides of the visual fields) hemianopia (B).
 Occipital lesions may spare the fibers from the macula (as in D)
because of the separation in the brain of these fibers from the
others subserving vision.

27. Optic pathway lesions
Anopia: Total loss of vision in one visual fields
Hemianopia: Loss of vision in one half of visual field
Homonymous: In the same halfs of both visual fields
Heteronymous: In the opposite halves of both visual fields
Quadranatanopia: Loss of vision in one foutrh of visual field. It can also be
homonymous and heteronymous.
Macular sparing: it is the unaffected amcular vision because of its bitemporal
representation.
Optic nerve Anopia
Medial fibers of optic
chiasma
Heteronymous hemianopia (Bitemporal)
Lateral fibers of optic
chaism
Heteronymous Hemianopia
Optic tract Homonymous Hemianopia
Optic radiation Homonymous Hemianopia with macular
sparing
Visual cortex Homonymous Hemianopia with macular
sparing (Superior or inferior)

28. REFERENCES
Berne & Levy
Best and Taylor’s
Boron Boulpaep
G K pal

29. THANK YOU
“The most pathetic person in the world is some one who
has sight but no vision.”
― Helen Keller