Visual System - Eye Movements Flashcards

1
Q

What is eye movement?

Why is eye movement important?

A

Voluntary or involuntary movement of the eye

Necessary for acquiring and tracking visual stimuli

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2
Q

What are the muscles and innervation of the eyes?

A

6 extraocular muscles

3 CNs - CN III, IV, VI

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3
Q

What is meant by:

Duction

Version

Vergence

Convergence

A

Duction = eye movement of one eye

Version = simulatenous movement of both eyes in the same direction

Vergence = simultaneous movement (abduction) of both eyes in the opposite direction

Convergence = Simulatenous adduction (inward) movement in both eyes when viewing a near object

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4
Q

What are the 2 speeds of eye movements?

A

Saccade - short, fast bursts (900 degrees/sec)

Smooth Pursuit - sustain, slow movement (60 degrees per second). Driven by motion of a moveing target across the retina

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5
Q

What are the 4 types of saccade?

A

Reflexive saccade to external stimuli
Scanning saccade
Predictive saccade to track objects
Memory-guided saccade

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6
Q

What are the 6 extraocular muscles of the eye?

A

They all attach from the eyeball to the orbit
Superior, inferior, medial and lateral recti = straight muscles
Superior and inferior oblique

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7
Q

What are the functions of the superior and inferior recti?

What is the function of the lateral and medial recti?

A
Superior = move eye up
Inferior = move eye down
Lateral = abduction 
Medial = adduction
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8
Q

What is thestructure and function of the superior oblique?

A

Attached high on the temporal side of the eye, muscle originates from the orbit, through the trochlea, and passes under the superior rectus
Moves the eye down and out (abduct)

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9
Q

What is the structure and function of the inferior oblique?

A

Attached low on the nasal side of the eye, passes over the inferior rectus
Moves the eye up and out

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10
Q

What muscles so the CNs: CN III, IV, and VI innervate?

A

CN III:

Superior Branch =
Superior Rectus – elevates eye
levator palpebrae superioris – raises eyelid (not shown)

Inferior Branch =
Inferior Rectus – depresses eye
Medial Rectus – adducts eye
Inferior Oblique – elevates eye
Parasympathetic Nerve – constricts pupil

CN IV:

Superior Oblique – depresses eye

CN VI:

Lateral Rectus – abducts eye

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11
Q

How are these extraocular muscles tested?

A

Isolate muscles = maximises its action and minimises the action of other muscles

Abduction – Lateral Rectus
Adduction – Medial Rectus
Elevated and Abducted – Superior Rectus
Depressed and Abducted – Inferior Rectus
Elevated and Adducted – Inferior Oblique
Depressed and Adducted – Superior Oblique
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12
Q

Where may a patient be asked to look?

Why are they not asked to look directly up or down?

A

Look left and right, then upper left and lower right, finally upper right, lower left

As more than one extraocular muscle contributes to the up and down movement of the eyes

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13
Q

What is meant by the terms:

Up (Elevation)
Supraduction
Supraversion

Down (Depression)
Infraduction
Infraversion

Right – Dextroversion

Left – Levoversion

Torsion

A

Up (Elevation)
Supraduction – one eye
Supraversion – both eyes

Down (Depression)
Infraduction – one eye
Infraversion – both eyes

Right – Dextroversion
Right Abduction
Left Adduction

Left – Levoversion
Right Adduction
Left Abduction

Torsion – rotation of eye around the anterior-posterior axis of the eye

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14
Q

What is 3rd nerve palsy?

How does it present clinically and why?

A

Palsy = damage or dysfunction

Droopy eyelid (loss of elevator palpebrae superioris)

Affected eye goes down and out because:

Unopposed superior oblique innervated by fourth nerve (down)

Unopposed lateral rectus action innervated by sixth nerve (out)

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15
Q

What is a 6th nerve palsy?

How does it present clinically?

A

Palsy = damage or dysfunction

Affected eye unable to abduct and deviates inwards

Double vision worsen on gazing to the side of the affected eye

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16
Q

What is nystagmus?

What is an Optokinetic Nystagmus?

A

Nystagmus = oscillatory eye movement

Optokinetic Nystagmus = smooth pursuit followed by fast phase reset saccade

17
Q

Why is the Optokinetic Nystagmus Reflex useful in children?

A

Testing visual acuity in pre-verbal children by observing the presence of nystagmus movement in response to moving grating patterns of various spatial frequencies

18
Q

What does it mean if someone has Otokinectic Nystagmus in response to moving grating?

A

The subject has sufficient visual acuity to perceive the grating pattern