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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
From Clincal Strabismus Management. 1999 W.B. Saunders Company, A.L. Rosenbaum and A.P. Santigo Editors.p 16
Muscle responsible for the primary movement from primary position
See: Action of the Extraocular Muscles from Primary Position
Hering's Law
The Law of Equal Innervation
Whenever an impulse for eye movement is initiated, the yoke muscle in the contralateral eye receives the same amount of innervation to contract.
Sherrington's Law
The Law of Reciprocal Innervation
Whenever a muscle receives an impulse to contract, its antagonist muscle will receive an equal amount of inhibitory input to relax
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
Grading Lateral Rectus Action on Versions
Grading Inferior Oblique Action on Versions
Grading Superior Oblique Action on Versions
