second cranial nerve, origin of optic nerve, couurse and termination of optic nerve, clinical presentation incase of optic nerve damage,

2. OPTIC NERVE
CN-II
DR SANA YASEEN
ANATOMY DEPARTMENT
KIMS

3. LEARNING OBJECTIVE
 Introduction to cranial nerve II
 Origin, course and termination of optic nerve.
 Pupillary light reflex
 Accomodation reflex
 Clinical aspect of optic nerve

4. INTRODUCTION
 The anatomical course of
the optic nerve describes
the transmission of special
sensory information from
the retina of the eye to the
primary visual cortex of
the brain.
 It can be divided into extracranial (outside
the cranial cavity) and intracranial
components.

5. EXTRACRANIAL
 The optic nerve is formed by the convergence of
axons from the retinal ganglion cells. These cells in
turn receive impulses from the photoreceptors of the
eye (the rods and cones).
 The nerve fibers arising from ganglionic cells makes
up the optic nerve.
 These fibers converges towards optic disc hence
piercing the three coats of an eyeball. (retina,
choroid, sclera)

8.  After its formation, the nerve leaves the
bony orbit via the optic canal, a
passageway through the sphenoid bone.
 It enters the cranial cavity, running along the
surface of the middle cranial fossa (in close
proximity to the pituitary gland).

11. INTRACRANIAL
 Within the middle cranial fossa, the optic nerves from each
eye unite to form the optic chiasm.
 At the chiasm, fibres from the nasal (medial) half of each
retina cross over to the contralateral optic tract, while fibres
from the temporal (lateral) halves remain ipsilateral:
 Left optic tract – contains fibres from the left temporal
(lateral) retina, and the right nasal (medial) retina.
 Right optic tract – contains fibres from the right temporal
retina, and the left nasal retina.

15.  Each optic tract travels to its corresponding cerebral
hemisphere to reach the lateral geniculate nucleus
(LGN), a relay system located in the thalamus; the
fibres synapse here.
 Axons from the LGN then carry visual information via a
pathway known as the optic radiation.
 Optic radiation pass through retrolenticular part of
internal capsule and terminates in visual cortex.
Brodmann area 17
 This area occupies upper and lower lips of calcarine
sulcus on medial surface of occipital lobe, where otic
impulses recieves consciousness.

17.  Association area 18 and 19 surrounding the brodmann
are 17, recieves fiber from primary visual cortex.
 Visual association areas are responsible for
interpretation of optic impressions as recognition of the
object, perception of color, depth and other aspect of
vision.

19. PUPILARY LIGHT REFLEX
 The pupillary light reflex involves adjustments in
pupil size with changes in light levels.
 The reflex is consensual: Normally light that is
directed in one eye produces pupil constriction in
both eyes.
 The direct response is the change in pupil size in the
eye to which the light is directed (e.g., if the light is
shone in the right eye, the right pupil constricts).
 The consensual response is the change in pupil size
in the eye opposite to the eye to which the light is
directed (e.g., if the light is shone in the right eye, the
left pupil also constricts consensually).

20. • Pupillary light reflex; direct and indirect

21. ACCOMODATION REFLEX
 The accommodation response is elicited when
the viewer directs his eyes from a distant (greater
than 30 ft. away) object to a nearby object.
 The stimulus is an “out-of-focus” image.
 The accommodation (near point) response is
consensual (i.e., it involves the actions of the
muscles of both eyes).

22. CLINICAL

23. VISUAL FIELD DEFECTS

24. SUMMARY
Name: optic nerve
Numerological order: II
Funtion: NERVE OF VISION
Functional component: SSA
Origin: ganglionic layer of retina
Ends: visual cortex in occipital lobe