Lecture 13 - Extraocular Muscle And Eye Movements

Question 1

Why do we have 2 eyes?

Answer 1

Can perceive depth (stereoscopic vision)

Wider FOV than 1 central eye

Question 2

What is conjugate gaze?

Answer 2

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

Question 3

What is the visual axes?

Answer 3

The central point at which the eye rotates

Question 4

What is double vision called?

Answer 4

Diplopia

Question 5

What does misalignment of the visual axis cause?

Why?

Answer 5

Diplopia

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

Question 6

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

Answer 6

Diplopia should disappear

Question 7

What are the 2 main axes of the eye?

Answer 7

Visual axes
Orbital axes

Question 8

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

Answer 8

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

Question 9

Where do the extraoccular muscles originate from?

Answer 9

Apex of the orbit

Question 10

Where do all of the extra-ocular muscles insert?

Answer 10

Sclera of the eye

Question 11

How many extra-ocular muscles are there?

What axis do they run in line with?

Answer 11

6

In line with orbital axis

Question 12

What are the 6 extra-occular muscles?

Answer 12

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

2 oblique muscles:
Superior oblique
Inferior oblique

Question 13

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

Answer 13

LR6SO4(R3)

Question 14

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

Answer 14

Lateral Rectus = Abducens nerve (VI)

Superior Oblique = Trochlea nerve (IV)

Rest of muscles = Occulomotor nerve (III)

Question 15

Go to the last slide and label image 1:

Answer 15

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

Question 16

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

Answer 16

Superior oblique

Question 17

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

Answer 17

Equal and opposite pull
(Agonists = antagonists)

Constant tone

Question 18

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

Why is this important?

Answer 18

Agonists contract strongly and antagonists relax

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

Question 19

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

Why is this important?

Answer 19

Agonists contract strongly and antagonists relax

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

Question 20

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

Answer 20

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

Question 21

Go to the last slide and label image 2:

Answer 21

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

Question 22

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

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

Answer 22

Abduction/Lateral = lateral rectus

ADduction /medial = medial rectus

Question 23

What is the function of superior rectus?
From resting gaze

What its main function?

Answer 23

Elevation
Intorsion
Slight adduction

Main function is elevation

Question 24

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

Answer 24

Lateral gaze, then look up

Question 25

What is the main function of the inferior rectus? What are its functions from primary resting gaze?

Answer 25

Depresses eye Depression Extorsion Adduction

Question 26

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

Answer 26

Lateral gaze then look down

Question 27

What is the trochlea?

Answer 27

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

Question 28

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

Answer 28

Intorsion Abduction Depression when medial

Question 29

How can you isolate the functionality of the superior oblique?

Answer 29

When the eye is positioned medially its depressor action dominates

Question 30

What 2 muscles depress the eye? Which muscle dominates depression when the eye is positioned laterally and then medially?

Answer 30

Inferior rectus Superior oblique Lateral gaze = inferior rectus Medial gaze = superior oblique

Question 31

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

Answer 31

Extorsion Abduction Elevation when eyes medial

Question 32

How can you isolate the function of the inferior oblique?

Answer 32

When the eye is positioned medially the elevator action dominates

Question 33

What 2 muscles elevate the eye? Which muscle dominates elevation when the eye is positioned laterally and then medially?

Answer 33

Superior rectus Inferior oblique Lateral gaze = superior rectus Medial gaze = inferior oblique

Question 34

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

Answer 34

1 = superior rectus 2 = superior rectus and inferior oblique 3 = inferior oblique 4 = inferior rectus 5 = inferior rectus and superior oblique 6 = superior oblique

Question 35

What is a deviating eye/lazy eye called?

Answer 35

Strabismus

Question 36

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

Answer 36

Esotropic

Question 37

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

Answer 37

Lateral rectus Abducens Nerve (VI) LR6SO4(R3)

Question 38

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

Answer 38

Eye is adducted (esotropic) + elevated (hypertropic) Abduction and depression gone Superior oblique gone Superior oblique = Trochlea nerve (IV) LR6SO4(R3)

Question 39

What muscles elevate?

Answer 39

SR IO

Question 40

What muscles depress?

Answer 40

IR SO

Question 41

How do you test Lateral Rectus and Medial Rectus?

Answer 41

LR = abduct eye MR = ADuct eye

Question 42

How do you test Superior Rectus and Inferior Rectus?

Answer 42

SR = abduct eye (laterally) then look up IR = abduct eye (laterally) then look down

Question 43

How do you test Superior oblique and inferior oblique?

Answer 43

SO = Adduct eye then look down IO = adduct eye the look up

Question 44

What is strabismus?

Answer 44

Ocular misalignment

Question 45

What can cause strabismus/ocular misalignment?

Answer 45

Kids (congenital or develop in infancy) Adults (acquired pathology of neuromuscular junction, extraocular muscles or nerves supplying muscles)

Question 46

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

Answer 46

III, IV and VI

Question 47

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

Answer 47

Myasthenia gravis

Question 48

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

Answer 48

Eye adducted and elevated since VI innervates superior oblique Vertically displaced images Diplopia worsens when looking down Patient may have head tilt

Question 49

What can cause trochlea nerve damage?

Answer 49

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

Question 50

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

Answer 50

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

Question 51

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

Answer 51

Ptosis (severe since innervates skeletal portion of Levator Palpebrae superioris) Blown pupil Eyes down and out

Question 52

What can cause Occulomotor nerve (III) damage?

Answer 52

Micro vascular ischaemia but the pupil is spared Tumor Posterior communicatin artery aneurysm Uncal herniation to due increased Intracranial pressure

Question 53

What are the clinical features of an Abducens nerve injury?

Answer 53

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

Question 54

What can cause Abducens nerve injury?

Answer 54

Micro vascular ischaemia Tumor Raised intracranially pressure

Question 55

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

Answer 55

Trochlea nerve (VI)

Question 56

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

Answer 56

Occulomotor nerve (III)

Question 57

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

Answer 57

Abducens nerve (VI)