Visual System Eye Movements Flashcards
What are the two types of eye movement?
Voluntary
Involuntary
What is eye movements necessary for?
Necessary for acquiring and tracking visual stimuli
What facilitates eye movements?
Facilitated by the six extraocular muscles innervated by the three cranial nerves (III, IV and VI
What his Duction?
Eye Movement in One Eye
What is Version?
Simultaneous movement of both eyes in the same direction
What is Vergence?
Simultaneous movement of both eyes in the opposite direction
What is Convergence?
Simultaneous adduction (inward) movement in both eyes when viewing a near object
What are the two different speeds?
Saccade- short, fast burst
Smooth Pursuit - sustains slow movement
What are the features of saccade?
Reflexive saccade to external stimuli
Scanning saccade
Predictive saccade to track objects
Memory-guided saccade
What are the features of smooth pursuit?
Slow movement – up to 60°/s
Driven by motion of a moving target across the retina.
What are the 4 straight eye muscles?
Superior rectus
Inferior rectus
Lateral rectus
Medial rectus
What does the superior rectus do?
Attached to the eye at 12 o’clock
Moves the eye up.
What does the inferior rectus do?
Attached to the eye at 6 o’clock
Moves the eye down.
What does the lateral rectus do?
Also called the external rectus
Attaches on the temporal side of the eye
Moves the eye toward the outside of the head (toward the temple)
What does the Medial Rectus do?
Also called the internal rectus
Attached on the nasal side of the eye
Moves the eye toward the middle of the head (toward the nose)
What does the superior oblique do?
Attached high on the temporal side of the eye.
Passes under the Superior Rectus.
Moves the eye in a diagonal pattern down and out
Travels through the trochlea
What does the inferior oblique do?
Attached low on the nasal side of the eye.
Passes over the Inferior Rectus.
Moves the eye in a diagonal pattern - up and out.
What is the superior branch of the third cranial nerve responsible for?
Superior Rectus – elevates eye
levator palpebrae superioris - raises eyelid (not shown)
What is the inferior branch of the third cranial nerve responsible for?
Inferior Rectus – depresses eye
Medial Rectus – adducts eye
Inferior Oblique – elevates eye
Parasympathetic Nerve – constricts pupil
What is the trochlear nerve responsible for?
Superior Oblique – depresses eye
What is the abducens nerve responsible for?
Lateral Rectus – abducts eye
How do we test eye movements?
Extraocular Muscle Testing – Isolate muscle to be tested by maximizing its action and minimizing the action of other muscles
What movements correspond to each muscle? (isolation testing)
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
What is the name given to upwards movement of eyes?
Up (Elevation)
Supraduction – one eye
Supraversion – both eyes
What is the name given to downwards movement of eyes?
Down (Depression)
Infraduction – one eye
Infraversion – both eyes
What is the name given to right movement of eyes?
Right – Dextroversion
Right Abduction
Left Adduction
What is the name given to left movement of eyes?
Left – Levoversion
Right Adduction
Left Abduction
What is torsion?
Rotation of eye around the anterior-posterior axis of the eye
What are the main features of third nerve palsy?
Affected eye down and out Droopy eyelid (loss of elevator palpebrae superioris) Unopposed superior oblique innervated by fourth nerve (down) Unopposed lateral rectus action innervated by sixth nerve (out)
What are the main features of sixth nerve palsy?
Affected eye unable to abduct and deviates inwards
Double vision worsen on gazing to the side of the affected eye
What is nystagmus?
Oscillatory eye movement
What is optokinetic nystagmus?
Smooth Pursuit + Fast Phase Reset Saccade
Why is optokinetic nystagmus useful?
useful in testing visual acuity in pre-verbal children by observing the presence of nystagmus movement in response to moving grating patterns of various spatial frequencies
Presence of Optokinetic Nystagmus in response to moving grating signifies that the subject has sufficient visual acuity to perceive the grating pattern
