Ocular Motility Flashcards
Due to the direction of a muscles pull around the axes
Muscle action
Major effect on the position of the eye when the muscle contracts while the head is in primary position
Primary action
The additional effect a muscle has on the position of the eye
Secondary and tertiary action
Position of the eyes when fixating straight ahead. The eyes and head are both straight
Primary gaze
Around the X and Z axes of Fick (straight up, down, left and right). Purely vertical or horizaontal
Secondary positions
The Y axis (oblique muscle positions) as well as head tilt positions
Tertiary positions
How many cardinal positions
6
Why is primary gaze not a cardinal position?
Multiple muscles being used
Which gazes are cardinal gazes
Right secondary
Left secondary
All tertiary gazes
Positions where only 1 muscle in each eye is responsible for movements (in addition to the yoked muscle in the other eye)
Cardinal positions
The gaze position (one of the cardinal positions) where the effect of a muscle is best observed
Field of action
SR in OD is up and to the right
By moveing the field of action,
You can isolate and evaluate each muscle. This is where the muscle axis is parallel or perpendicular to the visual axis
What will the field of action always be
Cardinal
What two muscles give you pure primary action when the visual axis and the orbital axis are aligned at 23 degrees
IR and SR
What is the field of action for SR
23 degrees abducted, elevator
Doing what to the superior rectus makes it perpendicular to the muscle plane, becomes and intortor?
Adduction 67 degrees
Makes it 90 degrees to the muscle plane
Field of action for inferior rectus
Down and to the right (abducted 23 degrees) to make it a depressor
Doing what it the inferior rectus makes it an extortor
Adduction 67 degrees
Is the field of action always the same as the muscle action?
No
Examples of why the field of action is not always the same as muscle action
SO intorts, depresses, and abducts
-but depression by the SO is best seen in the ADDuction position. When the eye is aDDucted 51 degrees, the Visual axis and the direction of the muscle coincide. This the best position to evaluate the SO
Any weakness of the superior oblique can be seen as a
Depression in ADDUction
What does field of action help you do
Helps you to isolate if a deviation seen is from weakness of that muscles, a restriction of action from the antagonist or both
What are the RSRs field of action
Up and to the right, but the actions of the SR are elevation, intorsion, and adduction
Muscle plane/insertion of the SR and IR
Are along the orbital axes and the orbital axis is 23 degrees of the visual axis
Pair of muscle in the SAME eye that move the eye in opposite directions
Agonist-antagonist
-MR is the antagonist of the LR
Muscles in the same eye that move the eye in the same direction
Synergistic muscle
- IO and SR
- SO-IR
Pair of muscles, one in each eye, that produces conjugate eye movements (moves the eyes in the same directions)
Yoke muscles
-up and to the right is SR (OD), IO(OS)
The right inferior oblique is the yoked muscle of the left
Superior rectus
Increased innervation (and contraction) to one muscle is accompanies by a reciprocal decreases innervation to its antagonist in the SAME eye. Increased innervation to the LMR to contract makes the LLR relax. This helps in both versions and vergences
Sherrington law of reciprocal innervation
Sherrington law of reciprocal innervation for secondary left gaze
RMR has increased innervation while RLR does not. LLR has increased innervation while LMR does not
Sherrington law of reciprocal innervation for vergence eye movements
RMR has increased innervation while RLR does not, LMR has increases innervation while LLR does not one vergence eye movement
Sherrington law of reciprocal innervation for left head tilt
RIO and RIR have innervation to extort while RSO and RSR do not. LSO and LSR have innervation to intort OS while LIO and LIR do not
During conjugate eye movements, equal and simultaneous innervation flow to yoked muscles
Hering law of equal innervation
What law applies to innervation of yoked muscles
Hering law
When will you notice that the yoke muscle in the other eye reacting
When there is a palsy to a muscles
Hering law of Raquel innervation on secondary left gaze
RMR has increased innervation and LLR has increased innervation
Hering law of equal innervation for head tilt to the left
RIO and RIR have increased innervation and LSO and LSR have the same innervation to the left eye
The vertical rectus muscles and the oblique muscles are important to do what to prevent vertical deviations or torsional movements
Adjust their tone
During vertical and oblique versions, _________ stabilize the line of sight and prevent horizontal movements
Horizontal rectus muscles
The amount of innervation depends on
The fixating eye, the angle of deviation will vary based on which eye is fixating
When the unaffected eye is fixating
Primary deviation
Good eye is still fixating
When the paretic or restricted eye is fixating
Secondary deviation
Bad eye is fixating, this deviation will be bigger than primary because they have to have more innervation to do this
Why is a secondary deviation larger than a primary deviation
Because there is an increased innervation to move the paretic eye to fixation. The increased innervation also goes to the non-fixating eye which causes an excessive action and a larger deviation
Left lateral rectus palsy
Left eye will be turned in. If right eye is fixating, the left eye turns in because of the unopposed action of the antagonist (LMR). This is Sherrington law! This misalignment is a primary deviation
If the paretic eye is fixating in a left lateral rectus palsy
Additional innervation to the left lateral rectus to establish this. But an equal increased innervation also flows to the right medial rectus because of Hering law producing an excessive adduction of the right eye. This deviation is a secondary deviation and it will be greater than the primary deviation
Movement or rotation of one eye around the axes of Fick (monocular)
Duction
Evaluated with the other eye closed and having the patient move the eye in all directions of gaze
Binocular simultaneous and conjugate eye movements or rotation of both eyes
Versions
This is a binocular movement wher ethe 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 eye movements
Disconjugate eye movement where the eyes (visual axes) rotate in the opposite directions
Vergences
Both eyes rotate in to maintain binocular fixation, for instance, when reading
Convergence
Both eyes roatate out
Divergence
Rotation of superior portion of both eyes in
Incyclovergence
Rotation of superior portion of both eyes out
Excyclovergence
What is important for fusion
Vergences
