Control of Eye movements Flashcards by Staci Thomas

_________ are the vestibular information that normal head movements require

Vestibular information

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____ ________ _____ _________ is the proprioceptive information that is involved with eye movements

eye movement and position

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What is involved in selecting the visual target in a normal eye movement?

Brainstem and cortical areas

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What are the three things that help to achieve the control of the eye position

medial longitudinal fasciculus
reflexes
cerebral centers

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What is the main reflex that is involved in the eye movements?

The vestibuloocular reflex

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List the 4 supranuclear gaze control systems

saccadic
smooth pursuit
vestibular-ocular
vergence

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This gaze control system is the rapid eye movement that brings to object onto the fovea

Saccadic

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This supranuclear gaze control system keeps the moving image centered on the fovea

Smooth pursuit

your eyes are moving but your head is not; H test

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This gaze control system keeps the image steady on the fovea during head movements

vestibular-ocular

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This gaze control system keeps an image on the fovea when the object is moved near or far away

The vergence system

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Describe conjugate movements of the eye

The eyes move in the same direction

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What is the function of the vestibular eye movement

holds the image steady on the fovea during brief head rotations

eyes move opposite of the head movement so that you are able to stay focused on the eye movement (conjugate)

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What is the function of the smooth pursuit eye movement

holds the image of a moving target steady on the fovea

with a moving head; conjugate deviation toward the direction of movement of the object

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What is the function of the saccade eye movement

brings the image of an object of interest onto the fovea

rapid conjugate deviation toward the opposite side

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What is the function of the nystagmus quick phase

directs the fovea toward the oncoming visual scene during self rotation; resets the eyes during prolonged rotation

quick deviation toward the stimulated labyrinth

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What is the function of the optokinetic eye movement?

Holds the image of interest steady on the retina during sustained head rotation

maintains deviation of the eyes initiated by the vestibuloocular reflex ; quick deviation toward inhibited cerebellum

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What is the function of vergence

moves the eyes in opposite directions so that images of a single object are placed on both fovea

accommodation to near targets

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In the saccadic system the ______ ______ _______ are voluntary and the _______ ________ are reflexive

Frontal eye fields

Superior colliculus

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The ______ _______ _______ _______ is also known as the horizontal gaze center

Paramedian pontine reticular formation (PPRF)

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Describe the path of the saccadic system (horizontal system)

The rapid eye movement brings the image to the fovea

The frontal eye fields receive this info and it is sent to the PPRF on the contralateral side

These fibers project to CN VI and then to CN III via the medial longitudinal fasciculus and to the eye muscles that will allow the eyes to look left or right

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If the left PPRF is damaged, then the patient will not be able to look to the _______ for a saccade movement

left

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Where are the frontal eye fields located?

middle frontal gyrus

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If the right frontal eye fields are stimulated, the patient will look ______

left

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Describe the path of the saccadic system (vertical)

Rapid eye movement brings the image of the object on to the fovea

The frontal fields get this information and it is sent to the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) in the MIDBRAIN

This then travels to the CN IV and the CN III nuclei and causes the eye muscles to look up (conjugate)

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Where is the PPRF located?

In the pons

Where is the riMRF located?

in the rostral midbrain near the superior fasciculus and posterior commissure

If there is an enlargement of the pineal gland, what will occur to the field of vision?

If the gland is large enough to compress on the posterior commissure, then there will be a vertical saccades issue

If there is a lesion, or a blood supply issue to the area that encompasses the red nucleus, interstitial nucleus of Canal, and the oculomotor nucleus, what will happen clinically?

The patient will not be able to look down

What are some of the things that help to contribute to the reflex saccadic eye movements?

Supplementary and parietal eye movements and the superior colliculus

Describe in detail the various neurons that are needed throughout the control of saccadic movements 1. burst 2. tonic 3. pause

1. needs to be a pulse of neuronal firing in order to move the eyes to the target (burst) 2. The tonic neurons help to lock onto the target 3. The pause neurons help to inhibit the burst neurons so that no more movements happens and the target can be looked at

Where are all of the cells of the horizontal saccadic movements located?

pons

Where are all of the cells of the vertical saccadic movements located?

midbrain

Differentiate between the burst cells in the horizontal and the vertical pathways of the saccadic movements

Horizontal are located in the pontine paramedic reticular formation Vertical are located in the rostral interstitial nucleus of MLF (riMLF)

Differentiate between the tonic cells in the horizontal and the vertical pathways of the saccadic movements

Horizontal: nucleus prepositus hypoglossi Vertical: interstitial nucleus of Canal

Differentiate between the pause cells in the horizontal and the vertical pathways of the saccadic movements

Both are in the omnipause cells of the Raphe nuclei

How do you test the saccadic movements clinically?

Do something that makes the patient jump from one image to another Have the patient move their eyes to your fingers that are wiggling in the periphery of their vision

If there is a destructive lesion in the frontal gaze center, what happens?

eye deviation is towards the lesion like a stroke

If there is an irritation lesion (seizure) in the frontal gaze center, what happens?

The eye deviation is away from the firing gaze center

Describe the pathway of smooth pursuit

Occurs in the parietooccipital junction Information travels from the pontine nuclei to the vestibulocerebellum to the medial vestibular nuclei to the respective Cn nuclei

If the smooth pursuit movement is horizontal, what CN nuclei will be involved?

6 and 3

If the smooth pursuit movement is vertical, what CN nuclei will be involved?

3 and 4

If the left hemisphere is activated the eyes move to the ______ in smooth pursuit

left

Describe the pathway of the optokinetic movement

Information follows the same general pathway of the smooth pursuit movements The visual field travels to the nucleus reticularis of the pons and the nuclei of the accessory optic system of the optic tract, and to the vestibulocerebellum, vestibular nuclei and to the nuclei of CN III, IV, and VI

What is required in order for the optokinetic movements to be intact?

parietooccipital eye field

How do you test smooth pursuit movements clinically?

Patient visually tracks slow moving objects optokinetic tape

Lesion of the parietal lobe will cause a loss of the smooth pursuit movements (TOWARD/AWAY FROM) the lesion

TOWARDS!

Describe the vestibular-ocular system pathways

The head is turned to a side, which activates the labyrinth that is locates on that side via the semicircular ducts The information then travels via CN VIII to the vestibular nuclei to (horizontal-3 and 6) and (vertical- 3 and 4)

If you turn your head to the right, what way will your eyes move? Which semicircular canals are activated?

Your eyes will move to the left to try to offset the movement the right semicircular canals will be activated

What are two ways that you can test the vestibular ocular movements?

1. Doll's eye maneuver | 2. Ice water caloric test

What will be true of the vestibule-occular movements that are present in a comatose patient?

They will be absent; both the dolls eyes and the ice water calorics

This is characterized by impaired horizontal eye movements as a result from a lesion int he medial longitudinal fasciculus

internuclear ophthalmoplegia

What are the impaired eye movements that are seen in internuclear ophthalmoplegia?

weak adduction of the affected eye abduction nystagmus of the contralateral eye

In what chronic disease is a lesion in the MLF common?

Where is the MLF?

In the pons and the midbrain

If the patients left eye is not able to adduct and the right has a nystagmus characteristic with abduction, what is suspected?

A lesion of the left MLF

If the patient is not able to look left, what is the suspected lesion?

A lesion in the left nucleus of CN VI

If the patient is not able to abduct their left eye, what is the suspected lesion?

A left CN VI nerve palsy that is inhibiting the left lateral rectus

What are the three components that make up the near reflex?

1. convergence- image is on the fovea 2. accommodation- lens thickens so that the image is on the fovea 3. pupillary constriction- better optical performance (pupils narrow)

What is the pathway of the Near reflex?

1. Normal visual pathway tot he striate cortex 2. Visual association cortex 3. Information goes to the superior colliculus or the pretectal area or both 4. travels to the oculomotor nucleus, which stimulates the medial rectus motor neurons and the pre-ganglionic parasympathetic neurons of the edinger westphal nucleus

How do you test vergence clinically?

patient focuses on a near object

If a patient has a pupil that constricts in near reflex testing but does not constrict via the light reflex, what is the diagnosis?

An Argyll-Robertson pupil that is seen with neurosyphilis