extra ocular eye movement Flashcards
importance of eye movement
- the eyes move to initiate and maintain fixation by directing the line of sight , important to keep the image on the retina
- also important to follow objects thought saccades and pursuits
listing plane
cuts eye transverse into posterior and anterior segments
axes of fick
the glob rotates on the this
X axis
eye rotates up and down
Y axis
eye makes torsional rotations like a wheel
tilt head side to side
Z axis
eye rotates from side to side
“zide to zide”
Duction
movement or rotation of one eye around the axes of fick (monocular)
evaluated with the other eye closed and having the pt move the eye in all directions of gaze
version
binocular, simultaneous and conjugate eye movements or rotation of both eyes
torsion
twist of the eye clockwise or counterclockwise around the axes of fick
intorsion
top of the eye rotates towards nose
extorsion
top of the eye rotates away from nose
conjugate eye movements
binocular movement where the visual axis of both eyes are in the same direction to maintain fixation with both eyes. Both eyes move in the same direction, by the same amount
conjugate torsion
twists the eyes in the same direction, clockwise or counterclockwise when the head is tilted to the right or the left
vergence
disoncjugate eye movement where the eyes rotate in opposite directions
-looking at a pen close to nose, eyes are not looking in the same direction
convergence
both eyes rotate in to maintain fixation, for instance, when reading
divergence
divergence
both eyes rotate out, hard to see
How many extraocular muscles are there?
6
4 recti, 2 oblique
recti muscles
superior rectus
inferior rectus
medial rectus
lateral recuts
oblique muscles
superior oblique
inferior oblique
horizontal recti muscles
in primary gaze, they are horizontal movers around the vertical Z axis
Medial rectus
- moves the eye to the nose (ADDuction)
- innervated by CN3
- inserts 5.5mm from nasal limbus
lateral rectus
- moves eye away from the nose (ABduction)
- CN6
- inserts 6.9mm from temporal limbus
vertical recti muscles
similar to horizontal recti muscles, they also insert in front of the equator
superior rectus
- primary action is to move the eye up (elevation)
- secondary action: intorsion
- tertiary action: ADDuction
- CN3
- inserts 7.7mm from superior limbus
inferior rectus
- primary action-move the eye down (depression)
- secondary action- extortion
- tertiary-ADDuction
- CN3
- inserts 6.5mm behinf inferior limbus
Medial and lateral walls
45 degrees of each other. the orbital axis is about 23 degrees of the two walls.
in primary gaze, the orbital axis…
is at 23 degrees of the visual axis
What EOM run with the orbital axis?
Vertical recti (23 degrees of visual axis)
2 oblique muscles insert..
behind the equator at 51 degree angle with the visual axis
superior oblique
- primary action-torsion
- secondary-depression
- tertiary-abduction
- CN4
- passes through trochlea found between the superior and medial walls, reflects backwards and inserts in the posterior quadrant of the globe
inferior oblique
- primary action-extortion
- secondary-elevation
- tertiary-abduction
- CN3
- originates at a small depression at orbital floor. it inserts in posterior lower temporal quadrant of the globe close to the macula
EOM involved in abduction
- lateral rectus
- medial rectus
- inferior oblique
- superior oblique
EOM involved in adduction
- medial rectus
- superior rectus
- inferior rectus
six cardinal points
represent the positions of gaze where one muscle is responsible for the movement into that position
agonist-antagonist
pair of muscle in the same eye that move the eye in opposite directions
medial rectus is antagonist to the lateral rectus
synergist muscle
muscles in the same eye that move the eye in the same direction
inferior oblique and the superior rectus
Yoke Muscle
pair of muscles, one in each eye, that produce conjugate eye movements
Right inferior oblique is the yoked muscle of the left superior rectus
Sherrington Law of reciprocal innervation
increased innervation to one muscle is accompanied by a reciprocal decreased innervation to its antagonist in the same eye.
increased innervation to the left medial rectus to contract makes the left lateral rectus relax. This helps in both versions and vergences
Hearing Law of equal innervation
during conjugate eye movements, equal and simultaneous innervations flow to yoked muscles. This is useful when there is a palsy to a muscle, you will notice that the yoke muscle in the other eye will overact
purpose of evaluating ocular motility
assess the ability to maintain fixation (conjugate movements)
Equipment needed to assess ocular motility
penlight, small target or finger puppet
set up for assessing ocular motility
no glasses because you want to be able to see any misalignment, fully illuminated room
instructions to pt when assessing ocular motility
- fixate on penlight 40cm away
- follow penlight without moving head
- have pt report double vision, pain, strain, discomfort
- start in primary and do H pattern
- look for ease, accuracy, and extent of movement
how to report ocular motility assesment
full and smooth for accurate and full movements
if there is abnormalities noticed, note it
what to expect when assessing ocular motility
- full range of movement with no diplopia complaints
- end point nystagmus
end point nystagmus
eyes “beat” if you go over too far
order in which to assess ocular motility
- versions
2. ductions ONLY if there were any abnormalities
