Eye muscles - Extrinsic Flashcards
What set of muscles function is to move the eyeball
Extrinsic muscles
What is the two groups of extrinsic eye musles
4 sets of Recti Muscles
- Superior
- Inferior
- Medial
- Lateral
2 sets of Oblique Muscles
- Superior
- Inferior
What is an added exception to the extrinsic muscles
Levator palebare superiors
Where do the recti muscles arise from
Arise from the apex of the orbit from an annular fibrosis ring
What is the only extrinsic muscle that arises anteriorly
Inferior oblique - arises from the roof of the orbit anteriorly
Where does the superior oblique arise from
arise from the roof of the orbit posteriorly
What alternates the direction of the superior oblique
Trochlear turns the muscle back to the sclera
Where is the location of the levator palpebral superiors
Sits onto of the superior recti and innervates the upper eye lid
What is the function of the levator palpebral superiors
Elevates upper eye lid
What is the 6 binocular movements of the eye
Dextroelevation – up to right Levo-elevation – up and to the left Dextroversion – to the right Levo-version – to the left Dextro depression – down to right Levo depression – down to left
What is the unicular movements of the eye
Away from nose = adduction
Towards nose = abduction
Elevation
Depression
What two movements allow the image to remain straight when you tilt your head
Intorsion and extorsion
Define intorsion
top of eye ball moves and rotates to nose
Define extorsion
top of eye ball rotates away from nose
What does the opposing eye do if one eye intorts
Extrorts
What is the disadvantage of humans having more frontal binocular vision
Decreased visual field
What is the advantage of humans having more frontal binocular vision
Gives the ability of depth perception
two eyes see sought different image on the same object, therefore have a better understanding of how far way it is
What is the position of the eye in the orbit
Eyeballs angle outwards in orbit (but still look straight ahead)
How are the extrinsic muscles attached to the eye ball
The extrinsic muscles are attaches along the orbital axis
What is the implication of the muscles attaching to the orbital axis rather than the occipital axis mean
Most muscles have more than one action
What is the implication of the oblique muscles attaching posteriorly
so they pull posterior part of the eye ball up/down and the anterior part moves in the opposite direction
What muscle attachments are in the horizontal plane and what implication does this have on eye movement
Medial and lateral recti muscles
Simple movements:
Medial contact - adducts
Lateral contract - abducts
What allows the Inferior and superior recti to perform primary actions of elevation and depression
When the muscles become parallel to optical axis
What movements put the Superior and Inferior recti parallel to the occipital axis
When the Lateral recti abduct the eye
What allows the superior recti to intort and the inferior recti to extort
When the medial recti adducts the eye placing the superior and inferior recti muscle perpendicular to occipital axis
What is the primary function of the Oblique muscles
SO - Rotation inwards IO- Rotation outwards
What is the secondary function of the Superior and inferior oblique muscles
SO - depression
IO- elevation
What causes the superior oblique to intort
When eyeball is abducted
What causes the inferior oblique to extort
When the eyeball is abducted
When can the obliques elevate or depress the eye
when the eye is adducted
When can the superior and inferior rect elevate or depress the eye
when the eye is abducted
What is the 3 primary actions of the Superior recti
- Elevation
- Adduction
- intorsion
What is the 3 primary actions of the inferior recti
- Depression
- Adduction
- Extortion
What is the 3 primary actions of the inferior oblique
- Extorsion
- Elevation
- Abduction
What is the 3 primary actions of the Superior oblique
- Intorsion
- Depression
- Abduction
Define strabismus
Misalignment of the eyes (squint)
What is esotropia strabismus
Convergent squint
What is exotropia strabismus
Divergent squint
What is the two functional consequences of a squint
Amblyopia
Diplopia
Define amblyopia
= lazy eye
Where brain supresses the image of one eye leading to poor vision in that eye without any pathology
How and when is amblyopia best correctable
correctable in early years using eye patches to stimulate the “lazy” eye to work
define diplopia
double vision
When does diplopia usually occur in squints
due to nerve palsies
