Visual System - Eye Movements Flashcards
Define duction.
Eye Movement in One Eye
Define version.
Simultaneous movement of both eyes in the same direction
Define vergence.
Simultaneous movement of both eyes in the opposite direction
Define convergence.
Simultaneous adduction (inward) movement in both eyes when viewing a near object
What is saccade?
- Rapid, conjugate, eye movement
Short fast, burst up to 900 degrees/second
Voluntary and involuntary
What are the 4 types of saccade?
- Reflexive saccade to external stimuli
- Scanning saccade
- Predictive saccade to track objects
- Memory guided saccade
What is smooth pursuit?
- Sustains slow movement (up to 60 degrees/s)
Driven by motion of a moving target across the retina
Involuntary
What are the six extra-ocular muscles?
- Lateral Rectus
- Medial Rectus
- Superior oblique
- Inferior oblique
- Superior rectus
- Inferior rectus
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Which extra-ocular muscles are innervated by the oculomotor nerve (CNIII)?
- Medial rectus
- Superior rectus
- Inferior Oblique
- Inferior rectus
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Which nerve innervates the superior oblique?
- Trochlear (CNIV) nerve
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Which extra-ocular muscle is innervated by the abducens (CNVI) nerve?
- Lateral rectus
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What is the function of the superior rectus?
- Elevation of the eyeball
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What is the function of the inferior rectus?
- Depression of the eyeball
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In what position will the superior rectus elevate the eye maximally?
- Abducted position
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What is the function of the lateral / external rectus?
- Abduction of the eyeball
Moves eye toward the outside of the head
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What is the function of the medial rectus?
- Adduction of the eyeball
Moves eye toward the middle of the head
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What is the function of the superior oblique?
Moves the eye in a diagonal pattern down and out
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- Attached high on the temporal side of the eye
- Passes under the Superior Rectus
- Travels through the trochlea
What is the function of the inferior oblique?
Elevate and abduct the eye
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- Attached low on the nasal side of the eye
- Passes over the Inferior Rectus
Which muscle raises the eyelid?
- Levator palebrae superioris
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Which nerve innervates the levator palpebrae superioris?
- Oculomotor nerve
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Which specific nerve innervates the superior rectus muscle?
- The superior oculomotor nerve
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Which specific nerve innervates the medial rectus, inferior rectus and the inferior oblique?
- Inferior oculomotor nerve
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Which position is the lateral rectus muscle best tested?
- In the abducted position
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Which position is the medial rectus best tested?
- In the adducted position
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Which position is the superior rectus best tested in?
- Elevated and abducted position
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Which position is the inferior rectus best tested in?
- Depressed and abducted position
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Which position is the inferior oblique best tested in?
- Elevated and adducted
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Which position is the superior oblique best tested in?
- Depressed and adducted
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Which muscles assist with convergence?
- Medial recti
What is the eye movements in a patient with third nerve palsy?
Down & Out
Unopposed superior oblique innervated by fourth nerve (down)
Unopposed lateral rectus action innervated by sixth nerve (out)
What happens to the eyelid in a third nerve palsy?
- Ptosis, drooping of the eye lid as the levator palpebrae superioris is affected
Which extra-ocular muscles are not affected in a third nerve palsy?
Superior oblique and lateral rectus
Which nerve is affected in a sixth-nerve palsy?
- Lateral rectus
What happens to eye movements in a sixth nerve palsy?
- Affected eye is unable to abduct and thus deviates inwards
What is nystagmus?
Oscillatory movement of the eye
What is an optokinetic nystagmus?
Smooth pursuit + Fast phase reset saccade
Which eye reflex is useful when testing the visual acuity in pre-verbal children?
Optokinetic nystagmus reflex
Observes the presence of nystagmus movement in response to moving grating patterns of various spatial frequencies
What is the optokinetic nystagmus reflex?
- Opto-kinetic Nystagmus is a form of physiological nystagmus, triggered by the presentation of a constantly moving grating pattern
- The eyes track along the grating motion, with smooth pursuit up to a limit, and resets the eye position to the centre, with a burst of fast saccade motion
- This results in cycles of slow phase smooth pursuit, alternating with fast phase reset saccade in the opposite direction