Control of Eye Movements Flashcards

1
Q

What are the important players in terms of controlling eye position?

A

MLF (medial longitudinal fasciculus, reflexes and cerebral centers)

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2
Q

What is saccadic movement? How about smooth pursuit?

A

Chopped up focus/rapid eye movements trying to focus an image on the fovea (scanning the room)
Smooth pursuit keeps a moving image centered on the fovea when head isn’t moving

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3
Q

What is vestibulo-ocular eye movement? How about vergence?

A

Holds image steady on fovea while head is moving

Keeps image steady on fovea when trying to see near and far

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4
Q

What is optokinetic eye movement?

A

keep image on retina while following a target

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5
Q

What are the major players involved in saccadic movement?

A

Frontal eye field (voluntary) and superior colliculus (reflexive)

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6
Q

What is the relay center for horizontal saccades and which part of the brainstem is it located? Which CNs are important for this?
What about vertical saccades?

A

Contralateral paramedian pontine reticular formation (PPRF/horizontal gaze center) in pons. CN III and VI
Rostral interstitial nucleus of the MLF (riMLF)/vertical gaze center in midbrain. CN IV and VI

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7
Q

Draw the pathway for horizontal saccades

A

Ok

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8
Q

Which frontal eye field and PPRF are active when eyes are turning left?
Lesion in the PPRF results in?

A

Right frontal eye field and left PPRF (and vice versa)

Both eyes cannot look to the side of the lesion

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9
Q

What happens when you have a pineal tumor?

A

Compression of the superior colliculus and posterior commissure = problems with vertical saccades

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10
Q

Damage to the nucleus of Cajal and red nucleus results in?

A

Problems with downward saccades since the circuit passes through this general area (medial midbrain)

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11
Q

What are the major players involved for reflexive saccades?

A

Supplementary and parietal eye fields and superior colliculus

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12
Q

Explain the mechanism for enabling saccadic control

A

Excitatory burst that moves eye towards the target > tonic neuron firing which locks the target on the fovea > pause neurons to hold the image still

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13
Q

What are the burst, tonic and pause cells for horizontal saccades?

A

Burst: PPRF
Tonic: Nucleus prepositus hypoglossi
Pause: omnipause cells of Raphe nuclei

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14
Q

What are the burst, tonic and pause cells for vertical saccades?

A

Burst: riMLF
Tonic: Interstitial nucleus of Cajal
Pause: Omnipause cells of raphe nuclei

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15
Q

How do you test saccadic movement?

A

Visually jump from one object to another

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16
Q

Saccades:
Destructive lesion to the frontal gaze center means?
Seizure (irritating) activity to the frontal gaze center means?

A

Eyes are deviated toward the lesioned eye field (that guy whose eyes are stuck to the left)
Eyes are deviated away from the lesioned eye field

17
Q

What are the major players of the smooth pursuit pathway?

A

Parieto-occipital junction (area 19)
Vestibulocerebellum
Medial vestibular nuclei
MLF

18
Q

Draw the smooth pursuit pathway

A

Ok

19
Q

Smooth pursuit: If we are moving eyes left, which hemisphere is stimulated?

A

Left hemisphere (and vice versa)

20
Q

Draw the optokinetic pathway

A

Ok

21
Q

How would you test smooth pursuit movements?

A

Visually track slow moving object (using optokinetic tape) and see optokinetic nystagmus

22
Q

When is optokinetic movement lost?

A

Lesions of parietal lobe equals loss of smooth pursuit towards side of lesion. No Optokinetic nystagmus when tape is moved towards side of damaged lobe

23
Q

Draw the vestibulo-occular reflex pathway again

A

OK

24
Q

How do you test vestibulo-ocular movements?

When are these tests absent?

A

Doll’s eye maneuver and ice water caloric

These will be absent in patient with brainstem level lesion

25
Q

What are doll’s eye maneuver and ice water caloric tests?

A

Doll’s eye - eyes move in opposite direction of head turning

Ice water caloric - nystagmus to irrigated ear

26
Q

Internuclear Ophtalmoplegia (INO)
Cause
Clinical

A
  • MLF lesion (ipsilateral to eye that cannot abduct)

- Weak adduction in affected eye and abduction nystagmus of contralateral eye

27
Q

Draw out the differences between INO (MLF lesion), CN VI nucleus lesion and CN VI palsy

A

Ok

28
Q

Compare and contrast INO, CN VI nucleus lesion and CN VI palsy

A

INO: affected eye cannot adduct, other eye has nystagmus
CN VI nucleus: both eyes cannot move to the side of lesion from central position
CN VI palsy: cannot laterally move affected eye

29
Q

What is needed to have the near reflex?

A

Convegence so image is on fovea (MLF is bypassed)
Pupillary constriction for better optical performance
Accommodation to thicken lens so image is focused on fovea

30
Q

Describe the pathway of the Near reflex

A

Normal visual pathway > visual association cortex > superior colliculus, pretectal area or both > CN III (adduction of MR) and EWN (pupillary constriction)

31
Q

How would you test vergence?

A

Make patient focus on a near object and you should see vergence

32
Q

Argyll Robertson pupil

A

Absent light reflex, but pupil constricts during near reflex testing
Associated wit heurosyphilis