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Vision Science 5 > Final Quiz > Flashcards

Final Quiz Flashcards

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1
Q

What is the amplitude of microtremors?

A

5-30 seconds of arc

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2
Q

Are microtremors smaller or bigger than microsaccades?

A

Smaller

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3
Q

What is the frequency of microtremors?

A

50-100 Hz

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4
Q

What are the two important characteristics of microtremors?

A

High frequency

Small amplitude

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5
Q

What is the average amplitude of a microsaccade?

A

6 minutes of arc

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6
Q

What is the range of amplitudes for microsaccades?

A

About 6 minutes of arc to 26 minutes of arc

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7
Q

What is the frequency of microsaccades?

A

120 Hz

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8
Q

What is the function of microdrift?

A

To prevent a stable image from fading

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9
Q

Microdrift is similar to what other eye movement?

A

Smooth pursuits

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10
Q

Which is slower, microdrift or smooth pursuits?

A

Microdrift

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11
Q

Which of the fixational eye movements is continuous and high frequency?

A

Microtremor

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12
Q

What is the usual range of microtremor amplitude?

A

5-20 seconds of arc

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13
Q

Microdrift generally has a velocity of less than __ minutes of arc.

A

20

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14
Q

Which fixational system is necessary to prevent the image of a stable object from fading?

A

Microdrift

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15
Q

What is the average amplitude of microsaccades

A

6 minutes of arc

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16
Q

What is the mean frequency of microsaccades?

A

120 Hz

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17
Q

Which of the fixational eye movements has no known function?

A

Microsaccades

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18
Q

Neuroanatomical control of fixation is a primarily active process that mostly involves which type of neurons?

A

Inhibitory

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19
Q

The neurology for fixation is meant to inhibit what?

A

Saccadic eye movements

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20
Q

What is anomalous slow drift?

A

When the eye slowly drifts away from the fixation target

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21
Q

Is the magnitude of anomalous slow drift larger or smaller than normal microdrift?

A

Larger

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22
Q

What is the usual amount of anomalous slow drift?

A

Up to 1 degree or more

Normal drift is between 6-26 minutes of arc

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23
Q

What is the most common cause of anomalous slow drift?

A

Amblyopia

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24
Q

What can cause anomalous slow drift?

A

Any condition that causes significant abnormality of foveal vision

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25
Q

What anatomical part of the eye dominates fixation?

A

The fovea

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26
Q

Which of the fixation anomalies can be described as sporadic, biphasic disruptions of fixation?

A

Saccadic intrusions

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27
Q

What is a general description of saccadic intrusions?

A

Inappropriate saccades during fixation

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28
Q

What causes an increase of normal saccadic intrusions?

A

Aging

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29
Q

Normal saccadic intrusion shows what kind of wave?

A

Square-wave jerk

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30
Q

What is the amplitude for normal saccadic intrusion?

A

0.5 - 3 degrees

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31
Q

Saccadic intrusions are associated with what diseases?

A

Cerebellar or brainstem diseases

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32
Q

Which of the fixation anomalies can be described as continuous?

A

Saccadic oscillations

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33
Q

What are saccadic oscillations?

A

Continuous disruptions of fixation

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34
Q

What does the graph of macrosaccadic oscillation look like?

A

A series of large saccades that straddle fixation (never on target)

35
Q

What are the two types of saccadic oscillations?

A

Macrosaccadic oscillation

Opsoclonus

36
Q

People with which of the saccadic oscillations can’t make a normal commanded saccade?

A

Macrosaccadic oscillation

37
Q

What is opsoclonus?

A

A saccadic oscillation without an intersaccadic interval, so there is no square wave, and they are never on target or steady

38
Q

Which is the most typical type of nystagmus?

A

Jerk nystagmus

39
Q

What are the two types of nystagmus?

A

Jerk nystagmus

Pendular nystagmus

40
Q

Which type of nystagmus doesn’t have any distinct phases?

A

Pendular nystagmus

41
Q

Jerk nystagmus has magnitudes up to how many degrees?

A

10 degrees

42
Q

Jerk nystagmus has rates up to how many Hz?

A

8 Hz

43
Q

How is jerk nystagmus described?

A

Rhythmic oscillations containing a slow phase

44
Q

What does the slow phase of jerk nystagmus represent?

A

Smooth pursuit

45
Q

Which type of nystagmus is generally congenital?

A

Pendular nystagmus

46
Q

Which fixational eye movement is necessary to prevent the image of a stable object from fading?

A

Microdrift

47
Q

T or F: Saccadic intrusion should never be seen in a normal individual during fixational testing.

A

False - small and infrequent ones are OK

48
Q

What does VOR do to stabilize retinal images during head motion?

A

Counter-rotates eyes at the same speed as the head

49
Q

When does OKN stabilize eyes?

A

During tracking of a large moving visual scene which causes an illusionary sensation of self-rotation

50
Q

What are the two types of vestibulo-ocular response?

A

VOR

Vestibular nystagmus

51
Q

VOR is a momentary movement of the eye meant to compensate for what?

A

A brief head movement

52
Q

Vestibular nystagmus is a response to what?

A

Continuous head motion

53
Q

Which of the vestibulo-ocular responses is an ongoing eye movement?

A

Vestibular nystagmus is an ongoing nystagmoid eye movement

54
Q

What organs are responsible for reading yaw, pitch, and roll?

A

Semicircular canals

55
Q

What two things make up the otolith organs?

A

Utricle and saccule

56
Q

What do the otolith organs do?

A

Direct head translation (heave, bob, surge)

57
Q

What EOMs does the horizontal semicircular canal connect with?

A

Ipsilateral - Medial Rectus

Contralateral - Lateral Rectus

58
Q

What EOMs does the anterior semicircular canal connect with?

A

Ipsilateral - Superior rectus

Contralateral - Inferior oblique

59
Q

What EOMs does the posterior semicircular canal connect with?

A

Ipsilateral - Superior oblique

Contralateral - inferior rectus

60
Q

In which plane is the utricular macula oriented?

A

Horizontal plane

61
Q

In which plane is the saccular macula oriented?

A

Vertical plane

62
Q

What are the three stimuli for VOR?

A

Rotational motion (pitch or yaw)
Translational (head linear acceleration)
Torsional (heat tilt/roll)

63
Q

What are the three aspects of the behavior of VOR?

A

Phase
Gain
Latency

64
Q

What is the phase of VOR supposed to be?

A

0 phase shift

65
Q

What is the fain of VOR supposed to be?

A

Depends on the frequency of head motion

Usually 0.5-5.0 Hz

66
Q

When is VOR gain induced?

A

During walking/running

67
Q

What is the VOR latency?

A

16 msec

68
Q

How is VOR gain equated?

A

Eye velocity / head velocity

69
Q

What is the ideal VOR gain?

A

-1.0

70
Q

What is VOR phase?

A

Temporal difference between head and eye movements

71
Q

In the dark, what is VOR gain?

A

-0.9

72
Q

In the dark, what is the VOR phase shift?

A

0

73
Q

In the light, what is VOR gain?

A

-1.0

74
Q

Describe torsional VOR

A

Tilting of the head from shoulder to shoulder

75
Q

What primarily mediates dynamic torsional VOR?

A

Vertical semicircular canals

76
Q

What is the gain range for dynamic torsional VOR?

A

-0.4 to -0.7

77
Q

What mediates static torsional VOR?

A

Otolith-ocular reflex from inputs of the utricles

78
Q

What is the gain range for static torsional VOR?

A

-0.1 - -0.24

79
Q

How is VOR controlled?

A

Pure reflex, with an arc of 3 or 4 neurons

80
Q

When the head rotates, which horizontal canal is stimulated (ipsi or contralateral)?

A

Ipsilateral

81
Q

When the head is rotated to the left, which horizontal canal is stimulated, and which muscles are activated?

A

Left (ipsilateral) horizontal canal, stimulating the left medial rectus, and the right lateral rectus

82
Q

What is the excitatory pathway of the horizontal VOR neural circuit?

A

Signal from horizontal semicircular canal to MVN, to contralateral abducens nucleus, to lateral rectus. (end 3-neuron arc)
The same abducens neurons cross the midline and ascend the MLF to innervate the contralateral medial rectus (end 4-neuron arc)

83
Q

What is the inhibitory pathway of the horizontal VOR neural circuit?

A

Signal from horizontal semicircular canal to MVN, to ipsilateral abducens nucleus, inhibits the lateral rectus (end 3-neuron arc)
Ascends the MLF to inhibit the contralateral medial rectus (end 4-neuron arc

Vision Science 5 (8 decks)

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