Eye Movements & its Classifications Flashcards
why do we need eye movements
to achieve precise, clear, & stable view of an object in the visual world
to achieve a precise, clear & stable view, it requires the image to be
held fairly stable on the foveal region
what is required to achieve a stable image on the fovea (foveation)
eye movement or oculomotor system
what is required to achieve a clear image
accommodation system
what system tracks objects in depth & also provides stereopsis & stereoacuity
vergence system
what system tracks objects sideways that is lateral
pursuit system
what are the 4 characteristics that eye movements can be classified into
function, conjugacy, direction, speed
what are the two types of function
to direct the fovea to an object of interest,
hold images steady on retina
what are the 3 factors that direct the fovea to an object of interest
saccades, smooth pursuit, vergence
which factor brings the image of the object of interest rapidly onto the fovea
saccades
which factor brings & stabilizes the image of a small moving target onto the fovea
smooth pursuits
which factor moves eyes in opposite directions so images of a single object are held simultaneously on both fovea
vergences
what factors hold images steady on the retina
fixation, vestibular, optokinetic
which factor holds the image of a stationary object on the fovea when the head is steady
fixation
which factor holds the image steady on the retinal during brief head movements
vestibular
which factor holds the image steady on the retina during sustained head movements or when the environment moves around the head
optokinetic
what are the two systems in conjugacy
versional & vergence
is versional conjugate or disconjugate
conjugate
movement of eyes in same direction to see objects positioned in various directions from us is called
pure versional saccadic
movement of eyes in opposing directions to see objects singly at different distances than us is called
pure symmetric vergence
duction is what kind of eye movement
monocular
version is what kind of eye movement
binocular
in monocular eye movements, explain the Fick’s x, y, & z axes
z-axis → abduction & adduction
y-axis → incyclotorsion & excyclotorsion
x-axis → elevation & depression
in binocular eye movements, explain the Fick’s x, y, & z axes
z-axis → dextroversion (left) & levoversion (right)
y-axis → dextrocycloversion & levocycloversion
x-axis → elevation & depression
what are the 5 types of version movements
fixation, saccadic, smooth pursuit, vestibular ocular reflex (VOR), optokinetic
stimulus & function of fixation
stationary target → stabilizes target onto fovea
stimulus & function of saccadic movement
step of target displacement → acquire an eccentric target onto fovea
stimulus & function of smooth pursuits
target velocity → to match eye velocity w/ target velocity to stabilize retinal image
stimulus & function of optokinetic movement
target or field velocity → maintain a stable image during sustained head movement
stimulus & function vestibular ocular reflex
head acceleration → maintain a stable image w/ target on fovea during transient head movement
what are the 2 types of vergence
convergence, divergence
what are the subsystems of vergence eye movements
disparity, accommodative, proximal, tonic
which subsystem does not track a target moving in depth
tonic
what is the stimulus for disparity
target disparity
what is the stimulus for accommodation
target blur
what is the stimulus for proximal vergence
apparent nearness or perceived distance of target
what is the stimulus for tonic vergence
baseline neural innervation (midbrain)
which eye movements have fast speed
saccades & vergence
which eye movements have slow speed
pursuits
what is the velocity of saccades
1,000deg/sec
