Visual System - Eye Movements Flashcards
What is eye movement?
Why is eye movement important?
Voluntary or involuntary movement of the eye
Necessary for acquiring and tracking visual stimuli
What are the muscles and innervation of the eyes?
6 extraocular muscles
3 CNs - CN III, IV, VI
What is meant by:
Duction
Version
Vergence
Convergence
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
What are the 2 speeds of eye movements?
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
What are the 4 types of saccade?
Reflexive saccade to external stimuli
Scanning saccade
Predictive saccade to track objects
Memory-guided saccade
What are the 6 extraocular muscles of the eye?
They all attach from the eyeball to the orbit
Superior, inferior, medial and lateral recti = straight muscles
Superior and inferior oblique
What are the functions of the superior and inferior recti?
What is the function of the lateral and medial recti?
Superior = move eye up Inferior = move eye down
Lateral = abduction Medial = adduction
What is thestructure and function of the superior oblique?
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)
What is the structure and function of the inferior oblique?
Attached low on the nasal side of the eye, passes over the inferior rectus
Moves the eye up and out
What muscles so the CNs: CN III, IV, and VI innervate?
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
How are these extraocular muscles tested?
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
Where may a patient be asked to look?
Why are they not asked to look directly up or down?
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
What is meant by the terms:
Up (Elevation)
Supraduction
Supraversion
Down (Depression)
Infraduction
Infraversion
Right – Dextroversion
Left – Levoversion
Torsion
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
What is 3rd nerve palsy?
How does it present clinically and why?
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)
What is a 6th nerve palsy?
How does it present clinically?
Palsy = damage or dysfunction
Affected eye unable to abduct and deviates inwards
Double vision worsen on gazing to the side of the affected eye
