Ocular Motility Flashcards by Sarah Heath

Due to the direction of a muscles pull around the axes

Muscle action

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Major effect on the position of the eye when the muscle contracts while the head is in primary position

Primary action

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The additional effect a muscle has on the position of the eye

Secondary and tertiary action

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Position of the eyes when fixating straight ahead. The eyes and head are both straight

Primary gaze

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Around the X and Z axes of Fick (straight up, down, left and right). Purely vertical or horizaontal

Secondary positions

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The Y axis (oblique muscle positions) as well as head tilt positions

Tertiary positions

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How many cardinal positions

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Why is primary gaze not a cardinal position?

Multiple muscles being used

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Which gazes are cardinal gazes

Right secondary
Left secondary
All tertiary gazes

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Positions where only 1 muscle in each eye is responsible for movements (in addition to the yoked muscle in the other eye)

Cardinal positions

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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

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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

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What will the field of action always be

Cardinal

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What two muscles give you pure primary action when the visual axis and the orbital axis are aligned at 23 degrees

IR and SR

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What is the field of action for SR

23 degrees abducted, elevator

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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

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Field of action for inferior rectus

Down and to the right (abducted 23 degrees) to make it a depressor

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Doing what it the inferior rectus makes it an extortor

Adduction 67 degrees

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Is the field of action always the same as the muscle action?

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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

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Any weakness of the superior oblique can be seen as a

Depression in ADDUction

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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