9-Ocular Motility Flashcards
Primary position of the eyes
Eyes fixate straight ahead and eyes and head are straight
Secondary position
Around the X ad Z axes of Fick. Purely vertical or horizontal
Tertiary position
Y axis and head tilt positions
How many cardinal positions do we have
6
What are cardinal positions
Positions where only 1 muscle in each eye is responsible for movement
What is the field of action
The gaze where the effect of a muscle is best observed
Any weakness of the SO can be seen as what
Depression in adduction
Why I’d the field of action important
Is helps you isolate if a deviation seen is weakness of that muscle, a restriction of action from the antagonist, or both
What is agonist antagonist of motility
Pair of muscles in the SAME eye that move in opposite direction
What are synergistic muscles
Muscles in the SAME eye that move in the SAME direction
What are yoke muscles
Pair of muscles, one in each eye, the produce conjugate eye movements (move eye in same direction)
What is the Sherrington law of reciprocal innervation
Increased innervation to on e muscle is accompanied by a decrease innervation to its antagonist in the same eye
What is the hering law of equal innervation
During conjugate eye movements, equal and simultaneous innervation flow to yoked muscles
Due to Herings law of equal innervation what will you see if there is a palsy in one muscle
The yoke muscle in the other eye will over react
What muscles are important for horizontal versions
Vertical rectus muscles and oblique muscles
What muscles are important for vertical versions
Horizontal rectus muscles
Primary deviation
Unaffected eye fixates
Secondary deviation:
Restricted eye fixates
Which is bigger a primary or secondary deviation?
Secondary, because there is increased innervation to move the affected eye
T/F Increase innervation goes to the non-fixating eye that causes excessive action and a larger deviation
True
Ductions
Movement of one eye sound the axes of Fick
Monocular
Versions
Binocular
Simultaneous and conjugate eye movements or rotation of both eyes
What are conjugate eye movements
Both eyes move in the same direction and same amount
Vergences are
Disconjugate eye movements where the eyes rotate or move in opposite directions
What are vergences important for
Fusion
Convergence
Both eyes rotate in
Divergence
Both eyes rotate out
Incyclovergence
Rotation of the superior portion of the eyes in
Excyclovergence is
Rotation of superior portion of both eyes out
T/F versions and vergences have similar late cites?
True
Which is faster acting movements? Versions or vergences?
Versions are faster
What is the infranuclear control
Cranial nerves (3,4,5) and the muscles they innervate
What is nuclear control
The cranial nuclei
What is Supranuclear control
Higher order sensory and motor system that plans and controls eye movements
Cerebral cortex, cerebellum, brainstem
What control system controls versions and vergences?
Supranuclear
What eye movements are included in versions?
Saccades Pursuits VOR OKN OKR
What are saccades?
Fast conjugate eye movements that work to keep images on the fovea. They require a strong force
What is the latency for saccades?
120-200 ms
When are saccades developed
1 year of age
Are saccades voluntary?
Yes, but they can be reflexive
What are pursuits?
Following eye movements
What is the latency for pursuits
125 ms
What is the peak velocity for pursuits
30-60 degrees per sec
What do pursuits match up
Eye velocity to target velocity
Are pursuits voluntary or involuntary
Involuntary
When do pursuits develop
3-4 months of life
What controls pursuits
Parietal lobe on same side
What are vestibule-ocular reflex (VOR)
Movements that stabilize a retinal image during brief head movements
What can the VOR be seen in
Dolls head maneuver
When do VOR develop
Horizontal at birth
Vertical is later
What is seen on dolls head maneuver (eye movement)
Eye moves opposite of head movement
What causes horizontal nystagmus
Vestibular damage
When is dolls head maneuver contraindicated
In trauma where spinal/cervical injuries
What is the caloric test? How does the eye move with different temperature water
Test that uses warm and cold water to set up a temperature gradient in the semicircular canals. Cold water the eye moves to opposite ear. Warm water it moves toward the same ear that water was injected in.
COWS
What is OKR responsible for
Continuous eye movements. It kicks in after VOR response fades with continuous head movements
What is rotational testing? What does it show?
Spin patient in a chair for about 20 seconds. Eyes will move in fast phase in opposite direction of rotation
What is OKN
Slow pursuit eye movement followed by fast corrective saccades. The head is still. It requires inpu from the visual system.
Has a longer latency
When is OKN developed
3-5 months
When is OKN used
In malingering, and cooperative patients
What does a + OKN tell you
That VA is at or better than the size of the stripes on OKN drum
What does a - OKN tell you
Nothing
How is OKN tested
With an OKN drum. Horizontal and vertical
Slide 33
Big chart
What do vergences ensure
Bifoveal fusion
What is fusional vergences
It requires the attention and cooperation of the cerebral cortex
What is tonic vergence
Constant innervaton tone to the EOMs when awake and alert. To keep the eyes straight forward because the eyes are naturally diverging.
What is proximal vergences
Induced due to awareness of near
What are accommodative vergences
Consistent increment of accommodative convergence with each dipter of accommodation gives AC/A ratio
What does a high AC/A produce
ET with accommodation
What dies a low AC/A do
Makes it harder to converge, less esotropic, more exotropic
