Eye Movements of the Visual System Flashcards
How many muscles innervate the eye?
6
What nerves innervate the eye muscles?
CN III (oculomotor) CN IV (trochlear) CN VI (abducens)
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 to version
Define convergence
Simultaneous adduction of both eyes when viewing a near object
Define saccades
Short, fast bursts of movement
What are the different types of saccades and what do they mean?
Reflexive saccade (to external stimuli)
Scanning saccade
Predictive saccade (to track objects)
Memory guided saccade
Define smooth persuit
Sustained slow movements of the eye
Driven by motion of slow moving target acoss retina
Where does the superior oblique move the eye?
Down and out
Where does the inferior oblique move the eye?
Up and out
What muscles does oculomotor innervate?
Superior branch:
Superior rectus and levator palpebrae superioris
Inferior branch:
Inferior and medial rectus, inferior oblique and parasympathetic nerve (pupil constriction)
What muscles does trochlear innervate?
Superior oblique
What is the role of the lateral rectus?
Moves eye towards the temple
What is the role of the medial rectus?
Moves eye towards nasal side of eye
What are the prefixes in terms of eye movement for elevation, depression, right and left?
Elevation= supra Depression= infra Right= dextro Left= levo
Define torsion as an eye movement
Rotation of eye around the anterior posterior axis of the eye
How does the affected eye appear in third nerve palsy- explain why
The eye goes down and out (the lateral rectus and superior oblique are unaffected as they aren’t innervated by CN III) and the eyelid is droopy (the levator palpabrae superioris isnt working)
How does the affected eye appear in sixth nerve palsy- explain why
Affected eye cannot abduct because the lateral rectus isnt working so it deviated inwards
When does double vision occur in sixth nerve palsy?
When gazing to the side of the affected eye
When is the optokinetic nystagmus reflex used and what does it indicate?
It is used to check that there is normal visual acuity in children who can’t speak yet
What is optokinetic nystagmus?
Smooth pursuit and fast phase reset saccade
