EOMs:introduction to eye movements & dynamics of extra-ocular muscle actions Flashcards
1
Q
what do all of the 6 EOMs work to produce
A
ocular movement around the centre of rotation
2
Q
what is the name of the EOM which is not apart of the other 6 EOMs
A
levator palpebrae superioris (LPS)
3
Q
which EOMs does the 3rd CN oculomotor superior division innervate
A
- SUPERIOR rectus
- levator palpebrase SUPERIORIS
4
Q
which EOMs does the 3rd CN oculomotor inferior division innervate
A
- medial rectus
- INFERIOR rectus
- INFERIOR oblique
5
Q
which EOM does the 4th CN trochlear innervate
A
superior oblique (i.e. the name of its pulley is called trochlear)
6
Q
which EOM does the 6th CN abducens innervate
A
lateral rectus (ie abducts the eye)
7
Q
where is the anatomical origin of the 4 recti muscles
A
at the annulus of zinn
8
Q
what does the mechanical origin of an EOM define
A
where the pull comes from e.g. for recti muscles it comes from behind
9
Q
where are the muscle pulleys of the 4 recti located
A
10mm posterior to equator of globe
10
Q
where are all 4 recti muscles inserted in the globe
A
anterior/in front of the equator
11
Q
which direction does the cornea rotate when each 4 recti muscle contracts
A
cornea rotates towards the body of the muscle itself
12
Q
what is the primary action of the medial rectus
A
inwards
13
Q
what is the primary action of the lateral rectus
A
outwards
14
Q
what is the primary action of the superior rectus
A
upwards
15
Q
what is the primary action of the inferior rectus
A
downwards
16
Q
where is the anatomical origin of the superior oblique EOM
A
annulus of zinn
17
Q
where is the anatomical origin of the inferior oblique
A
anterior infero-nasal corner
18
Q
what is the pulley of the superior oblique called
A
trochlear
19
Q
where is the trochlear (pulley) of the superior oblique located i.e. where does it pull from (mechanical origin)
A
anterior supero-nasal corner or orbital rim
20
Q
where does the inferior oblique pull from (mechanical origin)
A
- anterior & inferior to globe
- coupled to inferior rectus muscle
21
Q
so where are the mechanical origins of both obliques located
A
anterior to the globe (as oppose to recti which are all posterior to globe)
22
Q
where are both oblique EOMs inserted in the globe
A
behind the equator
23
Q
as each oblique muscle contracts, where does the cornea rotate
A
away from the body of the muscle itself
24
Q
what is the action of the superior oblique
A
downwards
25
what is the action of the inferior oblique
upwards
26
what type of arc around the limbus do the recti muscles form from their insertions
concave arc
27
how are the MR & IR insertions in relation to the limbus
concentric (follows the contour of the limbus adjacently)
28
how are the SR & IR insertions in relation to the limbus
- tilted slightly nasally
| - closest to limbus on nasal side
29
what type of arc around the limbus to the oblique muscles form, from their insertions
- convex arc
| - insertions fan out
30
how far behind the limbus is the MR inserted
5.5mm closest to limbus
31
how far behind the limbus is the IR inserted
6.5mm
32
how far behind the limbus is the LR inserted
7.0mm
33
how far behind the limbus is the SR inserted
7.5mm farthest from the limbus
34
which recti muscle does the IO muscle insertion lie under
lateral rectus
35
what does the posterior end of the IO overlie the position of
the fovea
36
which recti muscle does the SO muscle insertion lie under
superior rectus
37
in the primary position, where is the centre of rotation located
13.5mm behind the apex of the cornea
38
list the three axis of rotation of fick's axis
z axis
x axis
y axis
39
which direction does the z axis run
vertically through the eye
40
which direction does the z axis allow us to look
horizontally
41
which EOMs look horizontally around the z axis
medial rectus & lateral rectus
| Adduction and abduction
42
which direction does the x axis run
horizontally through the eye
43
which direction does the x axis allow us to look
vertically
44
which EOMs look vertically around the x axis
```
superior rectus
inferior rectus
inferior oblique
superior oblique
elevation and depression
```
45
which direction does the y axis run
obliquely through the eye (through the cornea)
46
which direction does the y axis allow us to run
cyclo rotation or torsionally
47
which EOMs look torsionally around the y axis
inferior oblique
superior oblique
superior rectus
inferior rectus
48
what is rotation of only ONE single eye termed
duction i.e. other eye is covered when doing adduction on a px etc
49
what are duction movements limited by
length of muscle + tendon, edge of orbit & soft tissue of the orbit
50
what does rotation of a SINGLE eye around the z axis produce
horizontal movement:
- adduction
- abduction
51
what does rotation of a SINGLE eye around the x axis produce
vertical movement:
- supraduction (elevation)
- infraduction (depression)
52
what is the duction (single eye) term for elevation
supraduction
53
what is the duction (single eye) term for depression
infraduction
54
what does rotation of a SINGLE eye around the y axis produce
torsional movement:
- excycloduction (extorsion) anti clockwise
- incycloduction (intorsion) clockwise
55
what is the duction (single eye) term for extorsion
excycloduction
56
what is the duction (single eye) term for intorsion
incycloduction
57
what are oblique movements a combination of
horizontal and vertical movements
| moves the globe into various oblique positions e.g. up and to the right or down and to the left etc
58
what is primary position of gaze
when the eyes are looking straight ahead with body and head erect
59
what happens to the contraction of a muscle when that muscle axis of rotation coincides with one of fick's axis or rotation e.g. z horizontal, x vertical or y torsional axis
contraction of that muscle will produce a rotation purely around that particular axis
e.g. if the lateral rectus axis of rotation coincides with the z axis, it will be purely horizontal or if it coincides with the x axis, it will be purely vertical
60
what is the muscle plane
a point where the muscle first touches the globe (tangental point) and the centre of rotation i.e. the orientation that is inserts into the eye
61
what is a muscle axis of rotation perpendicular to
the muscle plane (the orientation that it inserts into the eye) e.g. if a muscle inserts vertically it will only produce horizontal movements
62
in primary position what does the horizontal rectus muscles axis of rotation completely coincide with of fick's axis and hat contraction does that muscle produce as a result
z axis of rotation, produces a pure rotation around the vertical axis so NO vertical nor torsional component
63
which EOMs have only one action which is their primary and only action
medial rectus - adduction
| lateral rectus - abduction
64
in primary position which of fick's axis does the superior rectus coincide with
z ONLY, not with x or y
65
in primary position what is the primary action of the superior rectus
elevation
66
in primary position what is the secondary action of the superior rectus
incyloduction
67
in primary position what is the tertiary action of the superior rectus
adduction
68
what does RADSIN stand for
Recti
ADduct
Superiors
INtort
69
which muscle does the superior rectus lie adjacent to and what does that result in when the eye elevates
adjacent to the levator palpebrae superioris
| as eye elevates input to the LPS produces lid elevation
70
what angle does the superior rectus axis of rotation form with the x axis
23 degrees
71
what angle does the superior rectus axis of rotation from with the y axis
67 degrees
72
what does the superior rectus axis of rotation coincide with when the globe is abducted 23 degrees
x axis
73
when the superior rectus coincides with the x axis, what does it purely become
pure elevator
74
what does the superior rectus axis of rotation coincide with when the globe is adducted 67 degrees
y axis
75
when the superior rectus coincides with the y axis, what does it purely become
pure incycloduction
76
what angle does the inferior rectus axis of rotation form with the x axis
23 degrees
77
what angle does the inferior rectus axis of rotation form with the y axis
67 degrees
78
in primary position what is the primary action of the inferior rectus
depression
79
in primary position what is the secondary action of the inferior rectus
excycloduction
80
in primary position what is the tertiary action of the inferior rectus
adduction
81
what does RADSIN impose about recti muscles
recti ADDUCT
82
what does RADSIN impose about superior muscles
superiors INTORT
83
what does the inferior rectus axis of rotation coincide with when the globe is abducted 23 degrees
x axis
84
what does the inferior rectus axis of rotation coincide with when the globe is abducted 67 degrees
y axis
85
when the inferior rectus coincides with the x axis, what does it purely become
pure depressor
86
when the inferior rectus coincides with the y axis, what does it purely become
pure excycloduction
87
what angle does the superior oblique axis of rotation form with the x axis
54 degrees
88
what angle does the superior oblique axis of rotation form with the y axis
36 degrees
89
in primary position, what is the primary action of the superior oblique
incycloduction
90
in primary position, what is the secondary action of the superior oblique
depression
91
in primary position, what is the tertiary action of the superior oblique
abduction
92
when the superior oblique coincides with the y axis i.e. abducts 36 degrees, what does it purely become
pure incycloduction
93
when the superior oblique coincides with the x axis i.e. adducts 54 degrees, what does it purely become
pure depressor
94
what angle does the inferior oblique axis of rotation form with the y axis
39 degrees
95
what angle does the inferior oblique axis of rotation form with the x axis
51 degrees
96
in the primary position, what is the primary action of the inferior oblique
excylcoduction
97
in the primary position, what is the secondary action of the inferior oblique
elevation
98
in primary position, what is the tertiary position of the inferior oblique
abduction
99
which EOMs is the tertiary action of when in primary position
abduction
100
when the inferior oblique coincides with the y axis i.e. abducts 39 degrees, what does it purely become
pure excycloduction
101
when the inferior oblique coincides with the x axis i.e. adducts 51 degrees, what does it purely become
pure elevator
102
which EOMs have three actions in primary position
SR, IR, SO & IO
103
when the eye is adducted, what does the superior oblique produce
depression
104
when the eye is adducted, what does the inferior oblique produce
elevation
105
when the eye is abducted, what does the superior rectus produce
elevation
106
when the eye is abducted, what does the inferior rectus produce
depression
107
list which actions the superior oblique has in primary position
- elevation
- adduction
- intorsion
108
list which actions the inferior oblique has in primary position
- elevation
- abduction
- extorsion
