4. the visual system/pathway
consists of:
the retina
The optic nerve
The optic chiasma
The optic tract
The lateral geniculate body
The optic radiation
The visual cortex
The visual association cortex
BY Muhammad Ramzan Ul Rehman Nishtar Ken 4
5. optic nerve
axons of ganglion cells of the retina
optic chiasm
At optic chiasma, all fibers from the nasal halves of
the retina cross to the opposite side
crossed fibers join fibers from the opposite
temporal retina to form the optic tracts
These fibers synapse in the
dorsal lateral geniculate
nucleus (LGN)
from LGN to primary visual
cortex by way of the optic
radiation (geniculocalcarine
tract)
BY Muhammad Ramzan Ul Rehman Nishtar Ken 5
9. Homonymous contralateral
hemianopia with macular
sparing.
Macular sparing occurs
because lesion of visual
cortex don't destroy all
neurons that represent the
macula.
BY Muhammad Ramzan Ul Rehman Nishtar Ken 9
14. High degree of spatial fidility
Layers II, III and V receive temporal
fibers
Layers I, IV and VI receive nasal fibers
Layer I & II receive Y neurons
Layerr II & VI receive X cells
BY Muhammad Ramzan Ul Rehman Nishtar Ken 14
15. Area 17
located in the occipital lobe in the
calcarine fissure region extending
to the pole
large representation in visual
cortex for the macula (region for
highest visual acuity)
receives the primary visual input
BY Muhammad Ramzan Ul Rehman Nishtar Ken 15
16. visual association
cortex (area 18, 19)
responsible for
analyzing the visual
information
area for 3 dimensional
position, gross form,
and motion
area for color analysis
BY Muhammad Ramzan Ul Rehman Nishtar Ken 16
17. suprachiasmatic nucleus of the
hypothalamus
control of circadian rhythms??
pretectal nuclei
pupillary light reflex
accommodation of the lens
superior colliculus
rapid directional movement of both eyes
BY Muhammad Ramzan Ul Rehman Nishtar Ken 17
19. The eye is innervated by both
parasympathetic and sympathetic neurons.
Parasympathetic fibers arise in the Edinger-
Westphal nucleus, pass in the 3rd cranial
nerve to the ciliary ganglion.
Postganglionic fibers excite the ciliary muscle and
sphincter of the iris.
Sympathetic fibers originate in the
intermediolateral horn cells of the superior
cervical ganglion.
Postganglionic fibers spread along the corotid artery and eventually innervate
the radial fibers of the iris.
BY Muhammad Ramzan Ul Rehman Nishtar Ken 19
20. If a light is shone directly into one eye, its pupil constricts. This response is
known as the direct pupillary response.
The pupil of the other eye also constricts, and this is known as the
consensual response.
BY Muhammad Ramzan Ul Rehman Nishtar Ken 20
22. Fig. 16.07
BY Muhammad Ramzan Ul Rehman Nishtar Ken 22
23. When the amount of light entering
the eyes increases, the pupils
constrict.
Functions to help the eye adapt
extremely rapidly to changing light
conditions.
Direct light reflex: same pupil
constricts
indirect (consensual) light reflex:
pupil of the opposite eye constricts
BY Muhammad Ramzan Ul Rehman Nishtar Ken 23
25. miosis: decreasing of pupillary
aperture due to stimulation of
parasympathetic nerves that excite the
pupillary sphincter muscle
mydriasis: dilation of pupillary
aperture due to stimulation of
sympathetic nerves that excite the
radial fibers of the iris
BY Muhammad Ramzan Ul Rehman Nishtar Ken 25
26. Pupil that fails to respond to light but does respond to accommodation and
is very small in size.
It is an important diagnostic sign of CNS disease (syphilis).
BY Muhammad Ramzan Ul Rehman Nishtar Ken 26
27. The sympathetic nerves to the eye are occasionally interrupted . Interruption
occurs in cervical sympathetic chain.
BY Muhammad Ramzan Ul Rehman Nishtar Ken 27
28. One pupil remains persistently
constricted to a smaller diameter
than the pupil of the opposite eye
(miosis)
Drooping of Upper eyelid (ptosis)
Blood vessels on the corresponding
side of the face & head become
persistently dilated (flushing of
face)
Sweating can’t occur on the
affected side of the face
(anhydrosis)
BY Muhammad Ramzan Ul Rehman Nishtar Ken 28
30. Lister’s perimeter
Perimetry maps and quantifies the
visual field, especially at the
extreme periphery of the visual
field.
BY Muhammad Ramzan Ul Rehman Nishtar Ken 30
33. Physiologic blind spot: In all
perimetry charts, a blind spot
caused by lack of rods and cones in
the retina over the optic disc is
found about 15 degrees lateral to
the central point of vision, as
shown in the figure.
Scotoma
A blind spot in any other portion of
the visual field
BY Muhammad Ramzan Ul Rehman Nishtar Ken 33
34. nasal field located on the temporal side of the
retina
temporal field located on the nasal side of the
retina
interruption of the visual pathway at different
points leads to very specific visual field defects
“blind spot” located about 15 degrees lateral to
the central point of vision
no rods or cones in this area, called the optic
disc, exit point for axons of the ganglion cells
BY Muhammad Ramzan Ul Rehman Nishtar Ken 34
35. By Muhammad Ramzan Ul Rehman
BY Muhammad Ramzan Ul Rehman Nishtar Ken
35