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Head N Neck > Lecture 13 - Extraocular Muscle And Eye Movements > Flashcards

Lecture 13 - Extraocular Muscle And Eye Movements Flashcards

1
Q

Why do we have 2 eyes?

A

Can perceive depth (stereoscopic vision)

Wider FOV than 1 central eye

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2
Q

What is conjugate gaze?

A

When both the eyes move synonymously to ensure that the light/image focuses at the same point on each eye so that the image is perceived as one

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3
Q

What is the visual axes?

A

The central point at which the eye rotates

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4
Q

What is double vision called?

A

Diplopia

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5
Q

What does misalignment of the visual axis cause?

Why?

A

Diplopia

The visual axis misaligning means the images focused on different points in each eye so the brain cant fuse the images together

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6
Q

If a patient has Diplopia, what should happen when you cover either of the eyes?

A

Diplopia should disappear

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7
Q

What are the 2 main axes of the eye?

A

Visual axes
Orbital axes

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8
Q

Compare the visual axes and the orbital axes in relation to one another when the eye is in primary resting gaze:

A

Visual axis straight ahead
Orbital axis oblique laterally (follow the pyramid shape of the orbit)

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9
Q

Where do the extraoccular muscles originate from?

A

Apex of the orbit

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10
Q

Where do all of the extra-ocular muscles insert?

A

Sclera of the eye

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11
Q

How many extra-ocular muscles are there?

What axis do they run in line with?

A

6

In line with orbital axis

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12
Q

What are the 6 extra-occular muscles?

A

4 recti muscles:
Superior rectus
Inferior rectus
Lateral rectus
Medial rectus

2 oblique muscles:
Superior oblique
Inferior oblique

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13
Q

What is the mock chemical formula used to remember the innervation of all the extra-ocular muscles?

A

LR6SO4(R3)

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14
Q

What does the formulae LR6SO4(R3) tell us the innervation of the extraoccular muscles are?

A

Lateral Rectus = Abducens nerve (VI)

Superior Oblique = Trochlea nerve (IV)

Rest of muscles = Occulomotor nerve (III)

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15
Q

Go to the last slide and label image 1:

A

1 = trochlea
2 = superior oblique
3 = medial rectus
4 = superior rectus
5 = lateral rectus
6 = inferior rectus
7 = inferior oblique
8 = levator palpebrae superioris

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16
Q

What is the only extra ocular muscle that doesn’t arise form the common tendinous ring at the back of the orbit?

A

Superior oblique

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17
Q

What are the extra-ocular muscles doing during primary resting gaze?

A

Equal and opposite pull
(Agonists = antagonists)

Constant tone

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18
Q

What are the actions of the extra-ocular muscles when the eyes move?

Why is this important?

A

Agonists contract strongly and antagonists relax

Both eyes must ct simultaneously to ensure the visual axes remain aligned (conugate gaze) to prevent Diplopia

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19
Q

What are the actions of the extra-ocular muscles when the eyes move?

Why is this important?

A

Agonists contract strongly and antagonists relax

Both eyes must ct simultaneously to ensure the visual axes remain aligned (conugate gaze) to prevent Diplopia

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20
Q

What are the different types of movement the eye can do?

A

ABduction + ADduction
Elevation + Depression
Intorsion (Internal rotation) + Extorsion (external rotation)

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21
Q

Go to the last slide and label image 2:

A

1 = elevation
2 = depression
3 = adduction
4 = abduction
5 = INtorsion/internal rotation
6 = EXtorsion/external rotation

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22
Q

What muscles move the right eye laterally/right/abduction?

What muscles move the right eye medially/left/adduction?

A

Abduction/Lateral = lateral rectus

ADduction /medial = medial rectus

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23
Q

What is the function of superior rectus?
From resting gaze

What its main function?

A

Elevation
Intorsion
Slight adduction

Main function is elevation

24
Q

How can you isolate the main elevation function of superior rectus?

A

Lateral gaze, then look up

25
Q

What is the main function of the inferior rectus?

What are its functions from primary resting gaze?

A

Depresses eye

Depression
Extorsion
Adduction

26
Q

How can you isolate the main depressor function of the inferior rectus?

A

Lateral gaze then look down

27
Q

What is the trochlea?

A

Fascial belly/hook that redirects the superior oblique to insert on the upper lateral sclera

28
Q

What is the function of superior oblique from primary resting gaze?

A

Intorsion
Abduction
Depression when medial

29
Q

How can you isolate the functionality of the superior oblique?

A

When the eye is positioned medially its depressor action dominates

30
Q

What 2 muscles depress the eye?

Which muscle dominates depression when the eye is positioned laterally and then medially?

A

Inferior rectus
Superior oblique

Lateral gaze = inferior rectus

Medial gaze = superior oblique

31
Q

What is the function of inferior oblique from primary resting gaze?

A

Extorsion
Abduction
Elevation when eyes medial

32
Q

How can you isolate the function of the inferior oblique?

A

When the eye is positioned medially the elevator action dominates

33
Q

What 2 muscles elevate the eye?

Which muscle dominates elevation when the eye is positioned laterally and then medially?

A

Superior rectus
Inferior oblique

Lateral gaze = superior rectus

Medial gaze = inferior oblique

34
Q

Go to last slide and fill out the table labelled 3:

A

1 = superior rectus
2 = superior rectus and inferior oblique
3 = inferior oblique

4 = inferior rectus
5 = inferior rectus and superior oblique
6 = superior oblique

35
Q

What is a deviating eye/lazy eye called?

A

Strabismus

36
Q

What is it called when a patients eye is abnormally adducted when in resting gaze?

A

Esotropic

37
Q

If an eye is adducted in resting gaze (esotropic), what muscle is lost/weak?

What nerve innervates this muscle?

A

Lateral rectus

Abducens Nerve (VI)

LR6SO4(R3)

38
Q

Look at last slide and look at the image of the girl and answer the questions:

A

Eye is adducted (esotropic) + elevated (hypertropic)

Abduction and depression gone

Superior oblique gone

Superior oblique = Trochlea nerve (IV)

LR6SO4(R3)

39
Q

What muscles elevate?

A

SR
IO

40
Q

What muscles depress?

A

IR
SO

41
Q

How do you test Lateral Rectus and Medial Rectus?

A

LR = abduct eye
MR = ADuct eye

42
Q

How do you test Superior Rectus and Inferior Rectus?

A

SR = abduct eye (laterally) then look up

IR = abduct eye (laterally) then look down

43
Q

How do you test Superior oblique and inferior oblique?

A

SO = Adduct eye then look down

IO = adduct eye the look up

44
Q

What is strabismus?

A

Ocular misalignment

45
Q

What can cause strabismus/ocular misalignment?

A

Kids (congenital or develop in infancy)

Adults (acquired pathology of neuromuscular junction, extraocular muscles or nerves supplying muscles)

46
Q

What are the cranial nerves supplying the extra-ocular nerves that can lead strabismus if they’re damaged?

A

III, IV and VI

47
Q

What is an example of a neuromuscular junction condition that can cause strabismus?

A

Myasthenia gravis

48
Q

What are the clinical features of damage to the trochlea nerve and why?

A

Eye adducted and elevated since VI innervates superior oblique

Vertically displaced images
Diplopia worsens when looking down
Patient may have head tilt

49
Q

What can cause trochlea nerve damage?

A

Born with it
Head trauma
Tumour on trochlea nerve
Diabetic Macrovascular ischamia

50
Q

Why may a patient Tilt their head with Trochlea nerve damage?

A

Supplies superior oblique

SO does Intorsion so eye becomes extorted so patient tilts head to counteract

51
Q

What are the clinical presentations of Occulomotor nerve (III) damage?

A

Ptosis (severe since innervates skeletal portion of Levator Palpebrae superioris)

Blown pupil

Eyes down and out

52
Q

What can cause Occulomotor nerve (III) damage?

A

Micro vascular ischaemia but the pupil is spared

Tumor

Posterior communicatin artery aneurysm

Uncal herniation to due increased Intracranial pressure

53
Q

What are the clinical features of an Abducens nerve injury?

A

Affected eye adducted during resting gaze
Worsening Diplopia on affected eye side horizontal gaze

54
Q

What can cause Abducens nerve injury?

A

Micro vascular ischaemia
Tumor
Raised intracranially pressure

55
Q

Look at the last slide and identify what nerve is damaged on image 5:

A

Trochlea nerve (VI)

56
Q

Look at the last slide and identify what nerve is damaged on image 6:

A

Occulomotor nerve (III)

57
Q

Look at the last slide and identify what nerve is damaged on image 7:

A

Abducens nerve (VI)

Head N Neck (24 decks)

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