Eye Muscles, Movements, Testing Flashcards
What are 2 advantages of having Binocular Vision? (2 eyes)
What is Conjugate eye movement?
- Wider field of vision
- Depth perception (Enables 3D vision, Stereoscopic)
- When the eyes coordinate and move together
Why does Misalignment of the visual axes cause Diplopia?
Diplopia can be horizontal, vertical or diagonal
- ‘Image’ focused onto different areas of Retina in each eye
- Brain unable to ‘fuse’ images, hence we see 2 images
List the muscles that control movements of the eyeball
4 Recti;
- Superior
- Inferior
- Medial
- Lateral
2 Obliques;
- Superior
- Inferior
Most of the 6 eyeball movement muscles are innervated by what nerve?
What are 2 exceptions?
- CN III
- Superior Oblique: CN IV
- Lateral Rectus: CN VI
(Remember, LR6SO4)
Describe the attachments of the Recti and Oblique muscles
Obliques ;
- Originate from Apex of Orbit (except IO, arises from floor of orbital cavity anteriorly)
- Insert into Sclera
Recti;
- Originate from a common Tendinous Ring (Fibrous cuff surrounding the optic canal)
- Inser into Sclera
Name a muscle that originates from the Orbital Apex but does not move the Eyeball
Levator Palpebrae Superioris
Explain why some of the 6 Extra-Ocular muscles have more than 1 action on eyeball movement
- Extra Ocular muscles are parallel with the Orbital Axis, not the Visual Axis
- Therefore some muscles attach at an oblique angle (The ones attaching to Superior and Inferior parts of eyeball)
At Primary Resting Gaze there is constant activity of the Extra-ocular muscles, with all their actions being balanced
Briefly, how does the Position of Gaze change?
- Greater pull exerted by certain extra-ocular muscles
- Their antagonistic extra-ocular muscles relax
What is Intortion and Extortion of the eye?
Intortion: Internal rotation (towards nose)
Extortion: External rotation
(Not the same as Ab/Adduction)
Which muscles are used in each eye to look;
- Horizontally right
- Horizontally left
- > Right;
- Right eye: Lateral Rectus
- Left eye: Medial Rectus
- > Left;
- Right eye: Medial Rectus
- Left eye: Lateral Rectus
What are 3 actions of Superior Rectus if starting from Primary Resting Gaze?
In what eyeball position does its function change and how?
- Elevation
- Slight Adduction
- Slight Intortion
- When eye is positioned Laterally, becomes a more powerful Elevator
What are 3 actions of Inferior Rectus if starting from Primary Resting Gaze?
In what eyeball position does its function change and how?
- Depression
- Slight Adduction
- Slight Extortion
- When eye is positioned Laterally, becomes a more powerful Depressor
Where do we consider the functional pull of Superior Oblique as coming from?
From area of its Trochlea (as it passes through here to insert into eye, almost like a pulley)
What are 3 actions of Superior Oblique if starting from Primary Resting Gaze?
In what eyeball position does its function change and how?
- Intortion
- Depression
- Slight Abduction
- When eye is positioned Medially, becomes a more powerful Depressor
What are 3 actions of Inferior Oblique if starting from Primary Resting Gaze?
In what eyeball position does its function change and how?
- Extortion
- Elevation
- Slight Abduction
- When eye is positioned Medially, becomes a more powerful Elevator
