Visual System - Eye Movements Flashcards
List two types of eye movements.
voluntary
involuntary
Why is eye movement necessary?
acquiring and tracking visual stimuli
Eye movements are facilitated by what muscles?
6 extraocular muscles
Extraocular muscles are innervated by?
CN III, IV, VI
What is 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 movement in both eyes when viewing a near object
What is saccade?
short fast burst of movement
up to 900 degrees /sec
List types of saccade.
reflexive saccade
scanning saccade
predictive saccade to track objects
memory-guided saccade
What is smooth pursuit?
sustained slow movement
up to 60 degrees/sec
What is smooth pursuit driven by?
motion of a moving target across the retina
The extraocular muscles attach (?) to (?)
eyeball
orbit
What are the four straight extraocular muscles?
superior rectus
inferior rectus
lateral rectus
medial rectus
What is the muscle action of the superior rectus? Where is it attached?
moves the eye up
attached at 12 o clock
What is the muscle action of the inferior rectus? Where is it attached?
moves the eye down
attached at 6 o clock
What is the muscle action of the lateral rectus? Where is it attached?
moves the eye towards the outside of the head
attaches on the temporal side of the eye
What is the muscle action of the medial rectus? Where is it attached?
moves the eye toward the middle of the head/toward the nose
attached on nasal side of the eye
Apart from the ‘x rectus’ extraocular muscles, what two other muscles are there?
superior oblique
inferior oblique
Where is the superior oblique attached?
high on the temporal side
The superior oblique passes under what muscle?
superior rectus
What is the muscle action of the superior oblique?
moves the eye down and out
The superior oblique passes through what important structure?
trochlea
Where is the inferior oblique attached?
low on the nasal side of the eye
The inferior oblique passes over what muscle?
inferior rectus
What is the muscle action of the inferior oblique?
moves the eye up and out
Superior rectus is innervated by?
superior branch of the oculomotor nerve (CN III)
LPS is innervated by?
superior branch of oculomotor (CN III)
Inferior rectus is innervated by?
inferior branch of the oculomotor nerve (CN III)
Medial rectus is innervated by?
inferior branch of the oculomotor nerve (CN III)
Inferior oblique is innervated by?
inferior branch of oculomotor nerve (CN III)
Superior oblique is innervated by?
trochlear nerve (CN IV)
Lateral rectus is innervated by?
abducens (CN VI)
3rd nerve palsy causes what eye issues?
affected eye moves down and out droopy eyelid (loss of LPS)
6th nerve palsy causes what eye issues?
affected eye unable to abduct and deviated 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
Optokinetic nystagmus reflex is useful for?
testing visual acuity in pre verbal children by observing presence of nystagmus movement in response to moving grating patterns of various spatial frequencies
