====== Actions of Extraocular Muscles with Strabismus ======

==== Ductions ====
Movement of a single eye in any direction 
  * adduction- medial/nasal movement 
  * abduction - lateral/temporal movement
  * sursumduction- elevation
  * infraduction- depression
  * incycloduction- superior limbus moves nasally 
  * excycloduction- superior limbus moves temporally 

==== Versions ====
Movement of both eyes in any direction. There are 9 cardinal positions of gaze including primary position. 
  * Primary gaze- straight ahead
  * Right gaze 
  * Left gaze
  * Upgaze
  * Downgaze
  * Up and Right gaze
  * Up and Left gaze
  * Down and Right gaze
  * Down and Left gaze 

===Primary Movers for each gaze position===
Describes which muscles contract when the eyes are moved from primary position to one of the other 8 gaze positions. These are based on the primary action of each muscle. These are called Yoke muscles. 
  * Right gaze- Right lateral rectus and Left medial rectus
  * Left gaze- Left lateral rectus and Right medial rectus
  * Elevation- Both superior rectus and Both inferior oblique 
  * Depression- Both inferior rectus and Both superior oblique 
  * Up and Right- Right superior rectus, Left inferior oblique 
  * Up and Left- Left Superior recuts, Left inferior oblique 
  * Down and Right- Right inferior rectus, Left superior oblique 
  * Down and Left- Left inferior rectus, right superior oblique 

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{{::versions_with_fields_of_action.jpg|}}
From Clincal Strabismus Management. 1999 W.B. Saunders Company, A.L. Rosenbaum and A.P. Santigo Editors.p 16
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**Muscle responsible for the primary movement from primary position**
{{::primary_eom_mover_from_primary_position.jpg|}}
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See: [[action_extraocular_muscles_primary_position|Action of the Extraocular Muscles from Primary Position]]
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==== Hering's Law ====
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**The Law of Equal Innervation** \\
When a voluntary eye movement is made, equal and simultaneous neural innervation is sent to the **yoke** muscles of both eyes.
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==== Sherrington's Law ====

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**The Law of Reciprocal Innervation**\\
When a muscle contracts, its **antagonist** receives simultaneous inhibition, allowing smooth, efficient movement.
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==== Synergist Muscles ====
^ Action          ^ Muscles                                             ^
| Elevation       | Superior Rectus and Inferior Oblique                |
| Depression      | Inferior Rectus and Superior Oblique                |
| Adduction       | Medial Rectus, Superior Rectus, Inferior Rectus     |
| Abduction       | Lateral Rectus, Superior Oblique, Inferior Oblique  |
| Excyclotorsion  | Inferior Oblique, Inferior Rectus                   |
| Incyclotorsion  | Superior Oblique, Superior Rectus                   |

==== Yoke Muscles ====

^ Gaze (Versions)   ^ Yoke Muscles           ^
| Right  | Right Lateral Rectus, Left Medial Rectus  |
|Left  |Right Medial Rectus, Left Lateral Rectus |
|Elevation|Both Superior Rectus and both Inferior Obliques|
|Depression|Both Inferior Rectus and both Superior Obliques|
|Up and Right|Right Superior Rectus, Left Inferior Oblique|
|Down and Right| Right Inferior Rectus, Left Superior Oblique|
|Up and Left | Left Superior Rectus, Right Inferior Oblique|
|Down and Left|Left Inferior rRctus, Right Superior Oblique|

==== Grading of Eye Muscle Action during Versions ====
  * overaction is graded +1 through +4 based on comparison to a standard photograph
  * underaction is graded -1 through -4 based on comparison to a standard photograph
  * Normal function is "0" 

 ===Grading Medial Rectus Action on Versions===

{{::medial_rectus_grading.jpg|}}

===Grading Lateral Rectus Action on Versions===
{{::grading_lateral_rectus.jpg|}}

===Grading Inferior Oblique Action on Versions===
{{::grading_inferior_oblique.jpg|}}

===Grading Superior Oblique Action on Versions===
{{::grading_superior_oblique.jpg|}}

====Quantification of Eye Misalignment====
see: [[measuring_strabismus|How to Measure Strabismus]]

{{tag>tutorial strabismus}}