vision Flashcards
eye movements: recognise the main eye movements and their functions, identify the main brain structures involved in each kind of eye movement, recognise the main disorders that can occur with each type of eye movement and identify the main types of nystagmus
types of eye movement
voluntary, involuntary
why is eye movement necessary
for acquiring and tracking visual stimuli
what does contraction of muscles cause
muscle to pull (in agonist-antagonist pairs)
define duction
eye movement in one eye
define version
simultaneous movement of both eyes in same direction
define vergence
simultaneous movement of both eyes in opposite direction
define convergence
simultaneous adduction (inward) movement in both eyes when viewing an object
2 speeds of eye movement
saccade (short fast burst), smooth pursuit (slow sustained movement)
4 types of saccade movement
reflexive saccade to external stimuli, scanning saccade, predictive saccade to track object, memory-guided saccade
what drives slow movement
motion of moving target across retina
what do extraocular muscles attach
eyeball to orbit
2 types of movement
straight, rotatory
four straight extraocular muscles
superior rectus, inferior rectus, lateral rectus, medial rectus
where does superior rectus attach to eye, and what is its associated movement
12 o’clock, moves eye up
where does inferior rectus attach to eye, and what is its associated movement
6 o’clock, moves eye down
where does lateral (external) rectus attach to eye, and what is its associated movement
3/9 o’clock, attached to temporal side of eye, moves eye towards outside of head (temple)
where does medial (internal) rectus attach to eye, and what is its associated movement
3/9 o’clock, attached to nasal side of eye, moves eye towards middle of head (nose)
what are the 2 oblique eye muscles
superior and inferior
where does superior oblique attach to eye, what does it pass under and through, and what is its associated movement
attached high on temporal side, passes under superior rectus, travels through trochlea, moves eye diagonally down and in
where does inferior oblique attach to eye, what does it pass over, and what is its associated movement
attached low on nasal side of eye, passes over inferior rectus, moves eye diagonally up and out
3 nerves innervating extraocular muscles
oculomotor (III), trochlear (IV), abducens (VI)
what 2 things are innervated by the superior branch of the oculomotor nerve
superior rectus (elevates eye), lid levator (raises eyelid)
what 4 things are innervated by the inferior branch of the oculomotor nerve
inferior rectus (depresses eye), medial rectus (adducts eye), inferior oblique (elevates eye), pupil (PSNS so constricts)
what muscle is innervated by trochlear nerve
superior oblique (depresses eye)
what muscle is innervated by abducens nerve
lateral rectus (abducts eye)
diagram of cranial nerve innervation, extraocular muscle and associated movement
slide 17
how is eye movement tested
require patient to move eyes in circle or specific direction depending on muscle investigated (maximise its actions whilst minimising actions of other muscles)
elevation of eye: one vs both
supraduction is one eye, supraversion is both
depression of eye: one vs both
infraduction is one, infraversion is both
right (dextroversion) of eye
right abduction and left adduction
left (levoversion) of eye
right adduction and left abduction
what is torsion
rotation of eye around its anterior-posterior axis
effect of third (oculomotor) nerve palsy
affected eye down and out, droopy eyelid, unopposed superior obique innervated by trochlear nerve (down), unopposed lateral rectus action innervated by abducens nerve (out)
effect of sixth (abducens) nerve palsy
affected eye unable to abduct and deviates inwards; double vision worsen on gazing to side of affected eye
what is nystagmus
involuntary (oscillatory) eye movement in infancy
what is the optokinetic nystagmus reflex used for in infants
tests visual acuity by observing presence of nystagmus movement in response to moving grating patterns of various spatial frequencies; if present, subject has sufficient visual acuity but still being developed
