EOMs and related topics

Question 1

How many EOMs are there?

Answer 1

Six EOMs per eye

Question 2

How many cranial nerves have motor control of the EOMs?

Answer 2

Three cranial nerves per eye

Question 3

Which cranial nerve innervates the medial rectus?

Answer 3

CN III Oculomotor Nerve

Question 4

Which cranial nerve innervates the superior rectus?

Answer 4

CN III Oculomotor Nerve

Question 5

Which cranial nerve innervates the inferior rectus?

Answer 5

CN III Oculomotor Nerve

Question 6

Which cranial nerve innervates the inferior oblique?

Answer 6

CN III Oculomotor Nerve

Question 7

Which cranial nerve innervates the levator palpebrae superioris?

Answer 7

CN III Oculomotor Nerve

Question 8

Which cranial nerve innervates the superior oblique?

Answer 8

CN IV Trochlear Nerve

Question 9

Which cranial nerve innervates the leteral rectus?

Answer 9

CN VI Abducens Nerve

Question 10

Which eye muscles are controlled by CN III?

Answer 10

Medial, superior, and inferior rectus, inferior oblique, and levator palpebral superioris

Question 11

What are the three types of eye movements?

Answer 11

Versions, vergences, and ductions.

Question 12

Define versions

Answer 12

Rotations of the two eyes such that their lines of sight move in the SAME direction

Question 13

Define vergences

Answer 13

Rotations of the two eyes such that their lines of sight move in the OPPOSITE directions

Question 14

What are the two types of versions?

Answer 14

saccadic and pursuit (smooth)

Question 15

Saccadic movements are ____ and ____.

a. fast or slow
b smooth or jerky

Answer 15

a. fast

b. jerky

Question 16

Moving eyes from one object to another requires which type of version?

Answer 16

Saccadic

Question 17

Which kind of version are voluntary or triggered by the appearance of an object in the peripheral field?

Answer 17

Saccadic

Question 18

When voluntarily shifting fixation from one point to another, as in reading, which type of version must you use?

Answer 18

Saccadic

Question 19

Which part of the brain controls saccades?

Answer 19

The frontal lobe

Question 20

What is the function of pursuits (smooth) eye movements?

Answer 20

Function is to maintain fixation on the object of interest (once it has been located by the saccadic system).

Question 21

Which kind of version is triggered by movement of an object near the fovea (central vision)?

Answer 21

Pursuits

Question 22

Pusuits movements are ____ and ____.

a. fast or slow
b smooth or jerky

Answer 22

a. slow

b. smooth

Question 23

Which part of the brain controls pursuits?

Answer 23

The occipital lobe

Question 24

What are the two types of vergence?

Answer 24

Convergence and divergence

Question 25

During convergence, which muscles are working and which way do the eyes turn?

Answer 25

Medial rectus contracts in both eyes, pulling the eyes to the nose.

Question 26

During divergence, which muscles are working and which way do the eyes turn?

Answer 26

Medial rectus relaxes and/or lateral rectus contracts OU, pulling the eyes out and away from the nose

Question 27

Define duction

Answer 27

Rotation of one eye under monocular conditions

Question 28

What are the two main types of duction

Answer 28

Abduction and adduction

Question 29

Define abduction

Answer 29

Lateral (temporal) rotation of an eye; movement of the eye away from the nose

Question 30

Define adduction

Answer 30

Medail (nasal) rotation of an eye; movement of the eye toward the nose

Question 31

Define supraduction

Answer 31

Movement of an eye upward

Question 32

Define infraduction

Answer 32

Movement of an eye downward

Question 33

Define levoduction

Answer 33

Movement of an eye to the left

Question 34

Define dextroduction

Answer 34

Movement of an eye to the right

Question 35

Define yoked muscle pairs

Answer 35

Muscles of two eyes which simultaneously contract to turn the eyes equally in the same direction.

ex. right medial rectus and left lateral rectus contract simultaneously to move the gaze to the left

Question 36

Sherrington’s Law of Reciprocal

Innervation

Answer 36

The CONTRACTION of each ocular muscle is accompanied by a simultaneous and proportional RELAXATION of its antagonist.

Question 37

Sherrington’s Law describes the signal sent by the brain to coordinate _____ pairs.

Answer 37

antagonistic

Question 38

The right medial rectus and the right lateral rectus are antagonists; as one contracts, the other must relax. This is an example of _____ Law.

Answer 38

Sherrington’s

Question 39

Simplified version of Sherrington’s Law

Answer 39

contraction = relaxation

Amount of CONTRACTION innervation given to a muscle must equal the amount of RELAXATION innervation given to its antagonist

Question 40

Hering’s Law of Equal Innervation

Answer 40

Innervation to the muscle of one eye is equal to that in the other eye, resulting in movement of the two eyes that is equal and symmetrical

Question 41

Heting’s Law describes brain signals that coordinate which type of eye movements?

Answer 41

versions

Question 42

Looking to the right requires equal innervation to the right lateral rectus and the lefter medial rectus. This is an example of _____ Law.

Answer 42

Hering’s

Question 43

____ Law states that the innervation to the yoke muscle in the non-fixating eye must equal the innervation to the corresponding agonist muscle in the fixating eye.

Answer 43

Hering’s

Question 44

Which tests are used to screen for EOM dysfunction?

Answer 44

H-pattern and O-pattern