Motor Control of Eye Movements

Question 1

what are the two types of eye movements and what do they do?

Answer 1

conjugate - eyes move in the same direction

vergence - focus shifts between near and far objects where the eyes move in opposite directions

Question 2

what are the two types of conjugate movement?

Answer 2

saccadic- rapid movement where vision moves from target to target (voluntary)

smooth pursuit- maintains image of moving target fixed on retina

Question 3

what are the two types of vergence movements?

Answer 3

convergence - visual axis of eyes converge (near focus)

divergence- visual axis of eyes diverge (far focus)

Question 4

what are the 6 extra-ocular muscles of the eye and the 3 cranial nerves that innervate them?

Answer 4

lateral rectus, medial rectus, superior rectus, inferior rectus, superior oblique and inferior oblique
CN III
CN IV
CNVI

Question 5

what is strabismus and what cranial nerve and muscle is could not functioning?

Answer 5

strabismus also called cross eye is when the lateral rectus muscle is not functioning due to CN VI (6th nerve palsy)

Question 6

what are the steps for a patient looking to the right?

Answer 6

left frontal eye field——> PPRF ——> right abducens nucleus ——-> deccusation ——-> right abducens nerve to lateral rectus of right eye and interneuron (LMLF) to left oculomotor nucleus/nerve to medial rectus of left eye

Question 7

what is a brainstem gaze center, what are the three centers and where is each located?

Answer 7

collection of neurons serving extra-ocular muscles
horizontal gaze center - located in pons

vertical gaze center- located in midbrain

vergence gaze center- located in the midbrain

Question 8

Telling a patient to look to the right will use what frontal eye field and what gaze center? What happens if there is a lesion?

Answer 8

left frontal eye field and the horizontal gaze center (PPRF)
both the patients eyes will not move

Question 9

what if there is a lesion in the left medial longitudinal fasciculus and you ask the patient to look to the right? what is this issue called?

Answer 9

the left eye will continue to look straight while the right eye will look to the right

left internal nuclear ophthalmoplegia

Question 10

what if there is a lesion to the abducens nerve and you ask the patient to look to the right?

Answer 10

the right eye will stay looking straight but the left eye will look to the right

Question 11

the MLF pathway (nerve) is highly myelinated, therefore what disease can cause issues in this pathway????

Answer 11

multiple sclerosis causing demyelination which will not allow signal to go through

Question 12

Where is the vertical gaze center, where do the fibers cross and where do they project to?

Answer 12

located in the rostral midbrain and fibers cross at the posterior commissure where the pineal gland is in close proximity where they synapze at oculomotor subnuclei

Question 13

What is the primary CN associated with the vertical gaze center and the muscles?

Answer 13

CN III, superior and inferior lateral rectus

Question 14

where is the vergence gaze center located and where do the neurons project?

Answer 14

located in the reticular formation of the rostral midbrain
neurons project to CN III for convergence and CN VI for divergence

Question 15

what are the four cortical gaze centers?

Answer 15

frontal eye field, parietal eye field, occipital eye field and temporal eye field

Question 16

the frontal eye field is involved in what types of movement and projects to what gaze centers?

Answer 16

voluntary saccadic movement
vertical and horizontal centers as well as superior colliculus

Question 17

parietal eye field influences what type of movement?

Answer 17

saccadic

Question 18

the temporal eye field influences what type of movement?

Answer 18

smooth pursuit

Question 19

the occipital eye field influences what type of movement and signals to which CN’s?

Answer 19

influences vergence movements, focus shifts from faraway or near target
signals to oculomotor (convergence) or abducens nuclei (divergence)

Question 20

what does LR6SO4AO3 stand for?

Answer 20

lateral rectus CN 6, superior oblique CN4, all other CN3

Question 21

if a patient has an affected left eye that is elevated and adducted which CN and muscle is affected?

Answer 21

superior oblique and CN 4

Question 22

superior oblique is referred to as the what muscle?

Answer 22

down and out

Question 23

what is the only way to test if your CN IV is functioning properly?

Answer 23

ask your patient to look medially then look down (superior oblique to depress an already adducted globe)