Ocular Motility Exam 2

Front 1

what is the purpose of saccades

Back 1

to place the image on the fovea as rapidly as possible

400-700 degree arc/sec

Front 2

saccadic pulse

Back 2

1. burst of activity ~8ms before the eye starts to move
2. overcomes orbital viscous drag
3. eye moves quickly from one position to another

Front 3

saccadic step

Back 3

increase in tonic innervation to MAINTAIN NEW POSITION in the orbit by counteracting the visco-elastic forces working to return the eye to the primary position

Front 4

saccadic slide of innervation

Back 4

the transition between the end of the pulse of innervation and the beginning of the step

Front 5

Saccades: there are lawful relationship between...

Back 5

amplitude of movement
peak velocity
duration

Front 6

what is the relationship between amplitude and peak velocity

Back 6

larger amplitude have greater peak velocities

Front 7

what does the westheimer's experiment tell us about the saccadic system

Back 7

1. saccadic system can react to only ONE STIMULUS at a time
2. refractory period: during which a second saccade CAN NOT be initiated after the first

Front 8

saccadic reaction time

Back 8

interval between the appearance of a target of interest and the onset of the eye movement:

~200msec

Front 9

hick's law

Back 9

applies to saccadic programming: A log relationship exists between response time and the number of alternative choices

Front 10

when is the saccadic system slowed down and by how much

Back 10

~10% SLOWER

1.made in complete darkness
2.to remembered locations
3.anticipation
4.when in opp. direction to visual stimulus

Front 11

what does the saccadic velocity depend on...

Back 11

DIRECTION

movement towards the center is FASTER THEN towards the peripherals

Front 12

normometric saccade

Back 12

consist of a single accurate movment, having appropriate gain and dynamics

NORMAL

Front 13

what is normal gain

Back 13

ratio of amp. of initial eye movement to amp. of target movement

~92%

Front 14

hypometric saccades

Back 14

pulse amplitude too small
but pulse and step are matched appropriately

Front 15

corrective saccades

Back 15

when normal people UNDERSHOOT a target, they usually make a corrective saccade with a latency of 100 to 130ms

Front 16

hypermetric saccades

Back 16

pulse amplitude too LARGE
OVERSHOOT

Front 17

gissade

Back 17

mismatch between the saccadic pulse and step creating post saccadic drift

Front 18

gaze evoked nystagmus

Back 18

failure to hold gaze
clinically: drift of eye towards center

Front 19

neuroanatomic sites that influence saccadic pulse generation

Back 19

frontal eye fields
parietal lobes
superior collicus
cerebellum

Front 20

what causes saccadic omission

Back 20

1. threshold for detecting light ELEVATE during saccades
2. visual masking
3. motor information to sensory system
4. afferent information from proprioceptor

Front 21

saccadic omission

Back 21

during saccadic eye movement we do not appear to see blur

Front 22

when does the saccadic system develop

Back 22

1. initiate during neonate
2. accuracy inc. rapidly at 2months
3. infants use the coordinated head and eye movements to change gaze to a greater extent than adults
4. ability to change fixation with a single saccade develop by 1yr

Front 23

what did the kommerelle and colleagues experiment show

Back 23

the cns change saccadic innv. to best meet the visual needs of the HABITUAL view eye

Hering's Law of Equal Innervation
can be readjusted
to improve performance of the habitually fixating eye

Front 24

what are the ocular flutters

Back 24

back2back saccades
no intersaccadic interval
pathology of the fast phase sys.

Front 25

psychogenic flutters

Back 25

voluntary nystagmus: NOT pathology
not true nystagmus
horz. oscillation
back2back saccades
cycles, long or short (usually short)
5-8% of population
hereditary

Front 26

convergence retraction pulse

Back 26

1. DORSAL MIDBRAIN SYNDROME
2. asynchronous
3. not true convergence movement
4. saccadic disorder initiated by bursts

Front 27

Physiological Square Wave Jerk

Back 27

involuntary saccades
takes eye of target
after 130-200ms
6-8 per min

Front 28

treatment for SWJ

Back 28

diazepam
clonazepam
barbiturates

Front 29

frontal eye fields (saccades_)

Back 29

regions mapped with respect to size and direction of saccades

Front 30

parietal lobe (saccades)

Back 30

sending information related to localizing and attending to future targets in the field

Front 31

superior colliculus (saccades)

Back 31

receives input related to intended saccade direction and amplitude from eye field and parietal lobes

target selection
initiating saccades
contributing to their speed

Front 32

cerebellum (saccades)

Back 32

output to brainstem
maintain or adapts saccadic sign
control saccadic accuracy

Front 33

READ PAGE 6 of SACCADIC MOVEMENTS

Back 33

READ PAGE 6 of SACCADIC MOVEMENTS

Front 34

what is the purpose of the pursuit system

Back 34

1. smooth tracking of an object in space
2. pursue movement of a target on the retina
3. to match eye velocity w/ target velocity as closely as possible

Front 35

in pursuit, where may the image lay in relation to the retina

Back 35

on the fovea or parafovea

Front 36

when and where could the PURSUIT SYSTEM be triggered

Back 36

1. triggered by moving objects in the far visual periphery
2. can be triggered before a saccade can be programmed

Front 37

foveal lesions may impair...

Back 37

smooth pursuit of small targets

Front 38

smooth eye movement generation with relationship to perception

Back 38

usually we CAN NOT generate smooth eye movement without any perception of movement

Front 39

initial acceleration in respects to horizontal movement

Back 39

greater in the central than in the peripheral field

Front 40

initial acceleration in respects to vertical movement

Back 40

greater for stimulus in the lower visual field

Front 41

initial acceleration in respects to closing movement (ie coming at you) (TWSS)

Back 41

greater for targets moving towards the fovea

Front 42

lead and lag pursuit

Back 42

lead: puts the eye ahead of the target
lag: eye falls short of the object

Front 43

what is the significance of the Rashbass Exp.

Back 43

step-ramp stimulus
1. pursuit sys. responds to the ramp (MOTION)
2. the saccadic sys. takes into account the motion of the ramp, which brings the target back to the fovea, making saccades unnecessary

Front 44

how does field size effect the pursuit system

Back 44

1. full field stimulus=central 5-10 deg. of the visual field dominates the response
2. pursuit of small target leads to slip of images of the background on the retina

Front 45

how does stimulus size effect the pursuit system

Back 45

larger stimuli-enhances pursuit
1. due to stimulation of a larger area of the retina
2. allowing freedom to select and attend

Front 46

how does the background image effect the pursuit system

Back 46

~20% decrement in pursuit gain when pursuing a target as it moves across a TEXTURED background

Front 47

difference between pursuit and saccades

Back 47

pursuit: continuous
saccades: discrete with a refractory period

Front 48

anticipatory drift

Back 48

prior to onset of target motion
eye will start to move in anticipation

small <1.0deg/sec if the time of onset and direction of the target motion are unknown (up to 6deg/sec)

Front 49

how long does it take for the pursuit system to respond to a ramp target motion

Back 49

100msec

Front 50

what are the two type of pursuit responses

Back 50

1. open loop phase: the first ~140msec after initiation (driven by the target's retinal image velocity)
2. closed loop or steady state phase: pursuit is maintained by an internal signal

Front 51

what are the steps from beginning to end of the pursuit system

Back 51

0-20msec: initial eye acceleration (40-100deg/sec)

20-40msec: eye movement independent of the target stimulus characteristic and functions to initiate an eye movement in the correct dir.

40-100msec: loosely related to target velocity and eccentricity of target

after 100msec: pursuit is under visual feedback control (closed loop)

Front 52

what is acceleration saturation in the pursuit system

Back 52

target velocity increase progressively BUT eye acceleration does not increase by the same amount

Front 53

pursuit gain

Back 53

ratio:
(eye velocity/target velocity)

~0.90-0.95

Front 54

vertical pursuit vs. horizontal pursuit

Back 54

1. vertical NOT as effective as horizontal
2. lower gain
3. greater phase lag
4. more and larger corrective saccades

Front 55

what happens when you no longer want to pursuit a target (Offset of pursuit)

Back 55

1. off set latency is slightly less than onset (<100msec)
2. eye velocity DECLINE EXPONENTIALLY to zero (time constant 90msec)

Front 56

response latency

Back 56

80-150msec

target velocity low=response latency longer

Front 57

how can pursuit gain be reduced

Back 57

1. addition of either a stationary or a moving background
2. increase target amp. over the range of 5-20deg

Front 58

what are the effects of aging on pursuit

Back 58

1. 25% decrement in smooth pursuit tracking (reduced gain)
2. reduced initial acceleration
3. increase latency to initial velocity
4. increase distractibility (anticipatory saccades)
5. increase square wave jerks
6. increase saccade freq.

Front 59

how do you test pursuit system

Back 59

EOM as done in OTM

Front 60

disorder of pursuit system

Back 60

1. inability to follow the target in one direction
2. movement may break down into a series of small saccades

Front 61

development of pursuit system

Back 61

neonate-following with saccades
6weeks- tracking becomes mixed
3months- 22deg/sec

Front 62

MEDIAL RECTUS:
Primary
Secondary
Tertiary

Back 62

Primary: ADduction
Secondary:
Tertiary:

Front 63

LATERAL RECTUS
Primary
Secondary
Tertiary

Back 63

Primary: ABduction
Secondary:
Tertiary:

Front 64

INFERIOR RECTUS
Primary
Secondary
Tertiary

Back 64

Primary: DEPRESSION
Secondary: EXCYCLOTORSION
Tertiary: ADduction

Front 65

SUPERIOR RECTUS
Primary
Secondary
Tertiary

Back 65

Primary: ELEVATION
Secondary: INCYCLOTORSION
Tertiary: ADduction

Front 66

INFERIOR OBLIQUE
Primary
Secondary
Tertiary

Back 66

Primary: EXCYCLOTORSION
Secondary: ELEVATION
Tertiary: ABduction

Front 67

SUPERIOR OBLIQUE
Primary
Secondary
Tertiary

Back 67

Primary: INCYCLOTORSION
Secondary: DEPRESSION
Tertiary: ABduction

Front 68

agonist muscles

Back 68

contract to pull eye in that direction

Front 69

antagonist muscle

Back 69

relaxes

Front 70

field of action

Back 70

direction of gaze in which the muscle exerts its greatest contraction forces as an agonist

Front 71

synergistic muscles

Back 71

same field of action

for vertical gaze: SR/IO in moving eye UP

Front 72

antagonistic muscles

Back 72

opposite field of action

for torsion:
SR: intorsion
IO: extorsion

Front 73

saccadic Opsoclonus

Back 73

uncontrolled eye movement; rapid, involuntary, conjugate, fast eye movements w/o intersaccadic intervals