Q3: Neurology: Control Of Eye Movement

Front 1

What kind of eye movements must be explained? (6)

Back 1

1) Vestibulo-ocular reflex
2) Fixation reflexes
3) Smooth pursuit eye movements
4) Voluntary gaze
5) Vergence
6) Pupillary reflexes

Front 2

What do we need to understand? (4)

Back 2

1) Most eye movements are eye reflexes
2) Precise conjugate movemetns keep visual images on equivalent location- - so you don't get diplopia aka double vision
3) Lots of areas of brain contribute to eye movements
a)retina
b)vestibular system
c)cerebral cortex
d)cerebellum
e)superior collilculus

Front 3

What are 5 eye movements?

Back 3

1) Primary (looking straight forward)
2) Adduction and Abducation
3) Elevation
4) Depression
5) Extorsion and intorsion (focusin on the location of the superior part of the eye)

Front 4

Note about eye movements and muscles

Back 4

1) Except for the medial and lateral rectus, each muscle produces combined motions
2) EVERY movement above and below the plane involves at least 2 muscles

Front 5

What are the cardinal directions of gaze?

Back 5

See slide, table, picture

Front 6

** Esotropia

Back 6

Abnormal convergence of eyes. "Cross- eyed."

Front 7

Exotropia

Back 7

Abnormal divergence of eyes.

Front 8

Strabismus

Back 8

Eyes looking in different directions

Front 9

Amblyopia

Back 9

Wandering of an eye due to insufficient fixation reflex

Front 10

Vestibulo-ocular reflex

Back 10

Reflex movement of eyes equal and opposite to head motion

Front 11

Optokinetic reflex

Back 11

Reflex tracking of moving objects. "Railway nystagmus."

Front 12

Fixation reflex

Back 12

Reflex fixation on objects in vision.

It uses the same pathway as optokinetic reflex.

Front 13

Conjugate gaze

Back 13

Equal movement of eyes.

Front 14

Paramedian pontine reticular formation (PPRF)

Back 14

Pontine lateral gaze center

Front 15

Rostral interstitial nucleus of MLF

Back 15

Midbrain vertical gaze center

Front 16

Frontal eye field

Back 16

Region of the frontal lobe that initiates voluntary conjugate horizontal eye movements

Front 17

Occiptal eye field

Back 17

Visual association area responsible for fixation and optokinetic responses

Front 18

Nystagmus

Back 18

to and fro motions of the eyes. May be pendular (even to both sides) or jerk (fast on way with slow return)

Front 19

Pupillary light reflex

Back 19

Consensual constriction of pupil when light shines in either eye

Front 20

Consensual reflex

Back 20

Reflex response that is identical onboth sides to unilateral stimulus

Front 21

Vergence

Back 21

Convergence or divergence of the eyes (as fornear or far vision)

Front 22

Saccades

Back 22

Rapid eye movement used to acquire a target or to direct eyes toward an object of interest (reflexly or voluntarily)

Front 23

Tracking smooth pursuit

Back 23

Ability to follow a moving object

Front 24

Fixation

Back 24

Ability to lock eyes onto a target

Front 25

Accommodation

Back 25

Adjustment of the lens and pupil of the eye to focus on near objects

Front 26

What is the function of the OCULAOMOTOR NERVE/ NUCLEUS

Back 26

This is GSE innervation to all extraocular muscles (including levator palpebrae superioris (elevator of the eyelid) except lateral recrus and superior oblique.

Front 27

What does the Edinger-Westphal nucleus do?

Back 27

This nucleus provides GVE innervation to the ciliary ganglion
which, in turn, innervates the constrictor pupillae and ciliary muscles of the eye (for papillary
constriction and making the lens round).

Front 28

What does the Trochlear nerve/nucleus provide innervation for?

Back 28

provides GSE innervation to the superior oblique muscle

Front 29

What does the abducens nerve/abducens nucleus provide innervation for?

Back 29

provides GSE innervation to the lateral rectus muscle.

Front 30

VESTIBULO-OCULAR REFLEXES (VOR)

What do VOR induced eye movements compensate for?

Back 30

VOR is vestibular induced eye movements that
compensate for head movements.

Front 31

A) Where does the superior and medial vestibular nuclei
project?

B) What is it necessary for?

C) How can vestibular function be tested?

D) What are "Doll's eyes"?

*How does the VOR provide a test for brain stem?

Back 31

A) Superior/ medial vestibular nuclei project bilaterally to ocular nuclei and to
PPRF via the ascending MLF.

B) This reflex is necessary in order to focus on
an object when the head is moving.

C)Vestibular function can be tested by caloric
tests that examine eye movements when the
vestibular system are stimulated.

D) This term refers to
compensatory eye movements seen by
moving the head side-to-side in a comatose patient.

Front 32

A) What is TRACKING or SMOOTHING PURSUIT MOVEMENTS?

B) What does TRACKING involve?

Back 32

A) This refers to "locking" eyes on to a
perceived moving object. The eyes can
track objects in a very smooth manner.Smooth pursuit/tracking

B) It involves the "occipital eye field" and is
probably mediated through projections
from this area to the superior colliculus.

Front 33

C) Why is TRACKING an voluntary movement?

D)What other part of the brain does TRACKING involve?

Back 33

C) Tracking is a voluntary movement because
the cortex must designate the target of
interest, but a smooth sweep of the eyes
cannot be done voluntarily inabsence of visual stimuli.

D) Note that the neural pathway for tracking
involves the cerebellum and some of
the same pathways that are involved in
the vestibulo-ocular reflex (comparethe drawings.

Front 34

What is FIXATION REFLEX?

Back 34

This is essentially the same as smooth pursuit movements.
It refers to the ability to fixate when the object of interest or the person (or both) are moving
- Along with the VOR, this enables one to read a road sign when driving on a bumpy
road.

Front 35

What is RAILWAY NYSTAGMUS (optokinetic)?

Back 35

1) This refers to the to and fro eye movements made when
focusing on objects (e.g., telephone poles, fence posts, etc.) while sitting and looking out
the side window of a moving train.

2) It illustrates the powerful tendency displayed by normal individuals to fixate on moving
objects.

3) It is also called optokinetic nystagmus

Front 36

Describe neural control of voluntary conjugate deviation. (2)

Back 36

1) The control of conjugate lateral gaze and vertical gaze is by completely different pathways.

2) The control of conjugate lateral (horizontal) gaze is much better defined.

Front 37

Conjugate lateral (horizontal) gaze:
A) What is the highest recognizatble center for voluntary lateral gaze?

B) Where is it located and where does it project to?

Back 37

A) Frontal eye field


B)This is located just anterior to the lower portion of the precentral gyrus on the lateral
hemisphere.

This projects to the contralateral pons (the PPRF).

Front 38

Where is the PPRF located?

Back 38

The PPRF (paramedian pontine
reticular formation) is located near
the abducens nucleus in the pons and
therefore has also been called thparabducens nucleus.

Front 39

What does stimulation of the FRONTAL EYE FIELD result in?

Back 39

It results in horizontal eye movements away from the side of stimulation

Front 40

What does stimulation of the PPRF RESULT IN?

Back 40

Stimulation of the PPRF results in conjugate horizontal movement
toward the side of stimulation.

Front 41

What does the PPRF receive and where does it project?

Back 41

The PPRF receives multiple other
afferents involved in eye movement (including vestibular and tectal).

The PPRF projects directly to the abducens nucleus and to the contralateral
oculomotor nucleus via the medial longitudinal fasciculus (MLF).

Front 42

What does the abducens also connect to and what is the MLF also thought to be?

Back 42

The abducens nucleus also has connections to the contralateral oculomotor nucleus
through the MLF.

Therefore, the MLF can be thought to yoke the eyes together in horizontal gaze.

Front 43

A) What are the AFFERENT PROJECTIONS to the SUPERIOR COLLICULUS?

B) What does it project to?

C) What movement does the SUPERIOR COLLICULUS direct?

Back 43

A) This area receives many afferents especially from retina, inferior colliculus and cerebral
cortex.

B) It projects to spinal cord (tectospinal tract) and brainstem (tectoreticular) including PPRF.
These pathways traverse the MLF.

C) Directs movement of head and eyes towards novel stimulus. It also contains neurons that respond to moving visual stimuli

Front 44

What will electrical stimulation of the site in the superior colliculus cause?

Back 44

Electrical
stimulation of a site in the superior colliculus will cause the eyes and head to move
toward the part of the world which projects to that portion of the superior colliculus.

Front 45

What are the two portions of the cerebral cortex that are important to eye movement?

Back 45

1) Frontal Eye Field
2) Occipital Eye Field

Front 46

Describe 3 points about the FRONTAL EYE FIELD.

Back 46

1) It is located in the middle frontal gyrus.

2) It is considered to be the center for voluntary eye saccades in horizontal direction

3) It influences ocular nuclei via projections to the superior colliculus and contrallateral PPRF.

Front 47

Describe 2 points about the OCCIPITAL EYE FIELD.

Back 47

1) This is not a well-defined area in the anterior occipital lobe/posterior temporal lobe.

2) There are projections to superior colliculus that appear to subserve eye movements in
response to visual inputs to the occipital cortex and also projections to pontine nuclei
for smooth tracking and fixation (see above).

Front 48

What is VERTICAL GAZE?

Back 48

It is not driven by one cortical "center," but appears to be a diffuse cortical phenomenon.

Front 49

A) What are SACCADES?

B) What are they generated by? (2)

C) What happens during rapid movement?

D) What does rapid head movement cause?

Back 49

A) These are rapid, ballistic eye movements.
- Humans average 3/second.

B) Saccades are generated by the cerebral cortex and the superior colliculus.

C) Vision blurred during the rapid movement of a saccade.

D) The head turns 20-40 msec after saccade.
- The head movement causes opposite, compensatory eye movement to keep the eyes
fixed on target. This is controlled by vestibular feedback and is a vestibulo-ocular
reflex.

Front 50

A) Where are CONJUGATE VERTICAL EYE MOVEMENTS organized?

B) What has the rostral interstitial nucleus also been called and what area does it include?

C) Where does the rostral interstitial nucleus receive input?

D) What disease may diminish vertical gaze because of diffuse cerebral damage?

Back 50

A) Conjugate vertical gaze
Vertical eye movements are organized in the
rostral mesencephalic reticular formation,
also known as the rostral interstitial nucleus
of the MLF

B) The rostral interstitial nucleus of the MLF has
also been called the VERTICAL GAZE CENTER and
includes an area around the MLF, rostral to
the oculomotor nucleus

C) diffuse cortical areas

D) Alzheimer’s disease

Front 51

What does VERGENCE refer to and what is it controlled by?

Back 51

This refers to reflex convergence or divergence of the eyes in order to focus on objects moving toward or away from the viewer.

It is probably controlled by occipital cortical projections to the “vergence center” in the rostral midbrain. This is wired in parallel with the accommodation reflex (pupil
constriction and lens becoming round).

Front 52

CLINICAL APPLICATION:
What are two types of NYSTAGMUS?

Back 52

1) PENDULAR NYSTAGMUS

2) JERK NYSTAGMUS

Front 53

What is PENDULAR NYSTAGMUS?

Back 53

It is a regular and even to and fro movement of the eyes that is even in amplitude and speed to both sides. This is usually due to very weak fixation reflexes (often due to poor eyesight as a child).

Front 54

What is JERK NYSTAGMUS?

Back 54

1) It has a rapid and slow component.

2) It's described in terms of fast component- - and it's always pathologic when it occurs spontaneously in the mid position.

3) It is the most common finding in vestibular disorders.

4) It's the result of an imbalance in the vestibular system due to destructive or
irritating lesions.

Front 55

JERK NYSTAGMUS CONTINUED...

A) Induced postrotatory nystagmus (of Barany) ?

B) Induced caloric nystagmus?

C) End-point nystagmus?

Back 55

A) Rotation of body (about 10 rotations/20 seconds) sets endolymph in motion and
causing deflection of receptor cell sterocilia when the fluid continues to move
after the body is stopped.

B)
1) Irrigation of external auditory canal with warm or cold water results in convection currents in vestibular labyrinths and stimulates crista ampullaris by deflecting receptor cell sterocilia.

2) This can be used to test function of individual semicircular canals,especially the horizontal canal.

C) A few beats of nystagmus can occur normally with eye fatigue at the full end of
horizontal conjugate gaze.
It is always in the horizontal direction and in the direction of gaze

Front 56

1) Unilateral abducens nerve

Back 56

At rest, the left eye may deviate medially due to unopposed action of medial rectus.

Voluntary or reflex gaze toward the side of the lesion results in an internal deviation
(adduction), which causes diplopia.

Front 57

2) Unilateral abducens nucleus

Back 57

Involves direct or indirect (via the PPRF) connections with the oculomotor nucleus.

Lateral gaze paralysis - unable to move both eyes toward side of lesion because lesion disrupts connections between the abducens and oculomotor nucleus.

Front 58

3) MLF rostral to the abducens nucleus (internuclear ophthalmoplegia)

Back 58

This is commonly involved in multiple sclerosis.
With unilateral lesion (anterior internuclear ophthalmoplegia - INO) the patient is unable to move affected eye away from the side of the lesion.

2) There is also horizontal nystagmus in the abducting eye.
Bilateral lesions - cause disocciated horizontal eye movements with attempted gaze to either
side (reptilian stare).

Front 59

4) Frontal eye fields

Back 59

With damage, the patient is unable to voluntarily look away from side of lesion.

Reflex eye movements away fromshould be able to move eyes.

Front 60

5) Flocculo-nodular lobe

Back 60

Disequilibrium, with difficulty coordinating body and eye movements

Front 61

6) Unilateral trochlear nerve

Back 61

Eye deviates slightly medial and extorts

Head laterally flexed away from the side of lesion to limit diplopia.

Front 62

7) Rostral interstitial nucleus lesion

Back 62

Damage to this area will produce an inability to look up or down