Download Yaw - CLAS Users

Gross Anatomy
of the Eye
• Cornea at anterior
– Light passes to lens
• Retina at posterior
– sensory tissue
– sensory cells: rods
and cones
1. Cornea
2. Lens
3. Iris
4. Sclera
5. Macula
6. Optic Nerve Head
7. Retinal vessels
Sup.
8. Vortex Veins
Lat.
Med.
Inf.
Looking at the Retina
Macula- 3 by 5 mm area
at the posterior pole of
the eye
Fovea- in center of
macula,
free of blood vessels
contains only cone cells
Retinal
Anatomy
Back of the Eye
Front of the Eye
Extrinsic Eye Musculature
For moving eye within its
socket.
6 muscles per eyeball
Innervated by 3 Cranial
nerves
YAW
Eye Movements
Yaw: gaze shifts L/R
Pitch: gaze shifts up/down
Roll: eye rotates around
line of gaze (torsion)
PITCH
ROLL
• Adduction: shifting gaze toward midline
• Abduction: shifting gaze laterally
Extraocular
Muscles
Anterior View of Left Orbit
Oculomotor Muscle Actions
Muscle
Action
Nerve Supply
Sup. rectus
elevates & abducts eyeball
upper division of
oculomotor n. (III)
Sup. oblique
depresses & abducts eyeball
trochlear n. (IV)
Med. rectus
adducts the eyeball
lower division of
oculomotor n. (III)
Lat. rectus
abducts the eyeball
abducens n. (VI)
depresses & abducts eyeball
lower division of
oculomotor n. (III)
elevates & abducts eyeball
lower division of
oculomotor n. III)
raises the eyelid
upper division of
oculomotor n. (III)
Inf. rectus
Inf. oblique
levator
palpebrae
superioris
Sup.
Post.
Ant.
Inf.
3 branch of CN III to Inf Obl.
5 Sup. Rectus
7 Inf Rectus
8 Optic Nerve
10 Abducens Nerve
11 Oculomotor Nerve (CN III)
Ocular
Musculature
Superior Rectus (SR)
Inferior Rectus (IR)
Lateral Rectus (LR)
Medial Rectus (MR)
Superior Oblique (SO)
Inferior Oblique (IO)
CN Nuclei Important to
Oculomotor Function
Cranial Nerves III, IV, and VI
• III - Oculomotor
• IV - Trochlear
• VI - Abducens
III (Oculomotor) innervates:
1) Medial rectus
2) Superior rectus
3) Inferior rectus
4) Inferior oblique
Levator palpebrae sup
Pupillary sphincter
Ciliary muscle
IV (Trochlear) innervates:
• Superior oblique
VI (Abducens) innervates
• Lateral rectus.
Proprioceptive info from eye muscles
• comes through
Trigeminal nerve.
Eye Movements
•
•
•
•
•
Saccades—rapid shift in gaze
Pursuit—stabilize image of moving object
Fixation—stabilize image of still object
VOR—stabilize image during head motion
OKN—backup for when VOR decays to cont’d
head rotation
• Vergent movements—change depth of focus
– Accommodation-- automatic changes to see at different
distances which is chiefly brought about by changes in the
convexity of the lens. Horizontal vergence and accommodation
normally occur together. The two responses are accompanied by
an appropriate change in pupil diameter. The three concomitant
changes are known as the near-triad response.
Cortical
Areas:
Oculomotor
Control
• Occipital Eye Fields (areas 18 and 19)
• Frontal Eye Fields (area 8)
• Temporal Eye Fields (area 22)
Basic Eye Exam
Vestibulo-Ocular Reflex
VOR Pathways
• Vestibular nuclei
• Abducens N.
• Median
Longitudinal
Fasciculus
• Trochlear N.
• Oculomotor N.
Horizontal/Lateral Canal VOR
Anterior/Superior Canal VOR
Posterior Canal VOR
Anatomy &
Physiology of
a Horizontal
Saccade
Saccades
Pause cells inhibit
Burst Neurons
which stimulate:
III & VI (horizontal)
or
III & IV (vertical)