5. Eye Movement Flashcards
three categories of eye movements:
- conjugate: eyes move in SAME direction
- vergence: focus shifts between near and far objects
- vestibulo-ocular: keeps target fixed on retina during head movements
two types of conjugate eye movement
(eyes move in same direction)
- saccadic: rapid movement; vision moves from target to target
- smooth pursuit: maintains image of moving target fixed on the retina
two types of vergence eye movements:
eyes moving in opposite directions
- convergence: visual axis of eyes CONVERGE (near focus)
- divergence: visual axis of eyes DIVERGE (far focus)
describe the eye movements when looking at a painting
(free examination)
saccadic eye movements;
- tracing the attention given to the piece of art;
- extra attention given to identifying the faces
- more time spent on primary subjects
- also may depend on what you ask the patient to look at
describe the eye movements when looking at a painting
(give the ages of people)
- saccadic eye movements
-
Spending more time looking for visual cues of ages; looking at peoples’ faces
• Still includes fast, saccadic movements
list the type/# of extraocular muscles
- 4 recti muscles
- 2 oblique muscles
which cranial nerves innervate the extraocular muscles?
- CN III: oculomotor
- CN IV: trochlear
- CN VI: abducens
oculomotor nerve (CN III)
innervates which extraocular muscles?
- superior RECTUS
- inferior RECTUS
- medial RECTUS
- inferior OBLIQUE
trochlear nerve (CN IV)
innervates which extraocular muscle(s)?
superior oblique muscle
abducens nerve (CN VI)
innervates which extraocular muscle(s)?
LATERAL rectus muscle
muscle for:
elevation and upgaze
superior rectus
muscle for:
ADDUCTION of th eye; pulls nasal/medial direction
medial rectus
muscle for:
depression, downgaze
inferior rectus muscle
muscle for:
ABduction of the eye; lateral gaze/or temporal gaze
abducens nerve
brainstem gaze centers:
to gaze towards RIGHT
- Left frontal eye cortex –>
- left medial longitudinal faciculus –>
- right abducens nucleus:
- innervates right abducens nerve –> R lateral rectus mm.
- innervates left oculomotor nerve–> L medial rectus mm.
- Overall fxn: shifts gaze to right
what are the brainstem gaze centers,
and where are they located?
- horizontal gaze center – PONS (think: bridge)
- vertical gaze center – MIDBRAIN (think: “V”)
- vergence gaze center – MIDBRAIN (think: “micky mouse sign”)
brainstem gaze centers:
define
collections of neurons serving extraocular muscles
what is/where is the horizontal gaze center?
- paramedian pontine reticular formation, also known as PPRF or paraabducens nucleus
- found in the pons
fxn and how does the PPRF
(paramedian pontine reticular formation) work?
- involved in the coordination of eye movements, particularly horizontal gaze and saccades
- flow of information:
- frontal eye fields: plays an important role in the control of visual attention and eye movements
-
PPRF
- medial longitudinal fasciculus (MLF) –> oculomotor nerve –> Left medial rectus
- abducens nerve –> Right lateral rectus
CC: MLF (medial longitudinal fascicululs)
syndrome
aka: internuclear ophthalmoplegia
impacting internuclear pathway, and innervation from cortex –> abducens is still in tact, but communication between 2 cranial nerve nuclei is what is interrupted;
common in demyelinated diseases, such as multiple sclerosis
where is the vertical gaze center located?
where do fibers cross?
- located in rostral midbrain
- fibers cross at posterior commissure, w/ pineal gland in close proximity
where does vertical gaze center project to?
what is its function?
- projects to oculomotor subnuclei
- projects to muscles that do vertical motion: superior and inferior recti muscles
where is the vergence gaze center located?
where does it project to?
- located in rostral midbrain (reticular formation)
- projects to:
- CN III (convergence)
- CN VI (divergence)
which cranial nerve is associated w/ CONVERGENCE?
CN III
(oculomotor)
which cranial nerve is associated w/ DIVERGENCE?
CN IV
trochlear
what are the cortical gaze centers?
- FEF: frontal eye field
- PEF: parietal
- OEF: occipital
- TEF: temporal
frontal eye field:
fxn and projection
- fxn: origin of saccadic eye movements
- project to vertical and horizontal gaze centers & to superior colliculus
what does parietal eye field influence?
influence saccadic movements
what does temporal eye field influence?
influences smooth pursuit
occipital eye fields:
fxn, and action
- the origin of vergence movements
- focus shifts: faraway object <–> near target
- signal to oculomotor or abducens nuclei
CC: strabismus
(eyes are not aligned) / aka Cranial Nerve VI palsy
Lateral rectus is NOT working, so the medial rectus is pulling inwards
CC: Patient is cross-eyed and has trouble navigating stairs
vestibular testing indicates the patient has strabismus;
this is CN VI palsy (one eye looks directly at the object you are viewing, while the other eye is misaligned inward (esotropia, “crossed eyes” or “cross-eyed”), outward (exotropia or “wall-eyed”), upward (hypertropia) or downward (hypotropia).
how would you describe the location of the misaligned globe?
which muscle/cranial nerve is affected?
The LEFT eye is elevated and ADDUCTED
the superior oblique muscle is affected;
CN IV (trochlear nerve)
what is the normal movement for the superior oblique muscle?
“down and out”
by the tochlear nerve
cranial nerve IV supplies which superior oblique?
which tendon is associated?
it is the TROCHLEAR nerve; CN IV
tendon of superior oblique
actions of superior oblique?
primary action is intorsion (medial rotation);
secondary is ABduction and DEPRESSION
(inward and downward)
innervation and action of the inferior oblique muscle?
cranial nerve (III): oculomotor nerve
extorsion, elevation, ABduction
trochlea:
define
fascial sling in upper corner of the eye;
supports the superior trochlear muscle
name the axes of the globes (eyeball) in the orbits (eyesockets)?
Red axis paralell to nose bridge - Axis of eyeball
Blue axis obliquely - Axis of orbit
extraocular eye muscles and innervation
LR6 - SO4 - AO3
- Lateral rectus: CN 6 (abducens)
- Superior oblique: CN 4 (trochlear)
-
ALL OTHERS: CN 3 (oculomotor)
- superior rectus
- inferior rectus
- medial rectus
- inferior oblique
primary actions of the extraocular muscles
- Lateral rectus: ABDUCTION
- Medial rectus: ADduction
- Superior rectus: Elevation
- Interior rectus: Depression
- Superior oblique: Intorsion
- Inferior oblique: Extorsion
How to test the CN IV:
use the superior oblique to depress an ADDUCTED globe;
if patient is looking down to test superior oblique is working –> put the eye in an ADDucted position (and then see if it depresses the eye)
what is the purpose of the extra-ocular muscles?
to allow the eyes to remain fixed on an object even when turning the head side to side (i.e. ear to shoulder)
which cranial nerve palsy would result in a compensatory head tilt?
cranial nerve IV palsy –>
if the right eye is extorted and sl elevated causing double vision –>
to compensate the pt tilts head to the opposite side
