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Vision Science 5 > Final Quiz > Flashcards

Final Quiz Flashcards

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
What anatomical part of the eye dominates fixation?
The fovea
26
Which of the fixation anomalies can be described as sporadic, biphasic disruptions of fixation?
Saccadic intrusions
27
What is a general description of saccadic intrusions?
Inappropriate saccades during fixation
28
What causes an increase of normal saccadic intrusions?
Aging
29
Normal saccadic intrusion shows what kind of wave?
Square-wave jerk
30
What is the amplitude for normal saccadic intrusion?
0.5 - 3 degrees
31
Saccadic intrusions are associated with what diseases?
Cerebellar or brainstem diseases
32
Which of the fixation anomalies can be described as continuous?
Saccadic oscillations
33
What are saccadic oscillations?
Continuous disruptions of fixation
34
What does the graph of macrosaccadic oscillation look like?
A series of large saccades that straddle fixation (never on target)
35
What are the two types of saccadic oscillations?
Macrosaccadic oscillation | Opsoclonus
36
People with which of the saccadic oscillations can't make a normal commanded saccade?
Macrosaccadic oscillation
37
What is opsoclonus?
A saccadic oscillation without an intersaccadic interval, so there is no square wave, and they are never on target or steady
38
Which is the most typical type of nystagmus?
Jerk nystagmus
39
What are the two types of nystagmus?
Jerk nystagmus | Pendular nystagmus
40
Which type of nystagmus doesn't have any distinct phases?
Pendular nystagmus
41
Jerk nystagmus has magnitudes up to how many degrees?
10 degrees
42
Jerk nystagmus has rates up to how many Hz?
8 Hz
43
How is jerk nystagmus described?
Rhythmic oscillations containing a slow phase
44
What does the slow phase of jerk nystagmus represent?
Smooth pursuit
45
Which type of nystagmus is generally congenital?
Pendular nystagmus
46
Which fixational eye movement is necessary to prevent the image of a stable object from fading?
Microdrift
47
T or F: Saccadic intrusion should never be seen in a normal individual during fixational testing.
False - small and infrequent ones are OK
48
What does VOR do to stabilize retinal images during head motion?
Counter-rotates eyes at the same speed as the head
49
When does OKN stabilize eyes?
During tracking of a large moving visual scene which causes an illusionary sensation of self-rotation
50
What are the two types of vestibulo-ocular response?
VOR | Vestibular nystagmus
51
VOR is a momentary movement of the eye meant to compensate for what?
A brief head movement
52
Vestibular nystagmus is a response to what?
Continuous head motion
53
Which of the vestibulo-ocular responses is an ongoing eye movement?
Vestibular nystagmus is an ongoing nystagmoid eye movement
54
What organs are responsible for reading yaw, pitch, and roll?
Semicircular canals
55
What two things make up the otolith organs?
Utricle and saccule
56
What do the otolith organs do?
Direct head translation (heave, bob, surge)
57
What EOMs does the horizontal semicircular canal connect with?
Ipsilateral - Medial Rectus | Contralateral - Lateral Rectus
58
What EOMs does the anterior semicircular canal connect with?
Ipsilateral - Superior rectus | Contralateral - Inferior oblique
59
What EOMs does the posterior semicircular canal connect with?
Ipsilateral - Superior oblique | Contralateral - inferior rectus
60
In which plane is the utricular macula oriented?
Horizontal plane
61
In which plane is the saccular macula oriented?
Vertical plane
62
What are the three stimuli for VOR?
Rotational motion (pitch or yaw) Translational (head linear acceleration) Torsional (heat tilt/roll)
63
What are the three aspects of the behavior of VOR?
Phase Gain Latency
64
What is the phase of VOR supposed to be?
0 phase shift
65
What is the fain of VOR supposed to be?
Depends on the frequency of head motion | Usually 0.5-5.0 Hz
66
When is VOR gain induced?
During walking/running
67
What is the VOR latency?
16 msec
68
How is VOR gain equated?
Eye velocity / head velocity
69
What is the ideal VOR gain?
-1.0
70
What is VOR phase?
Temporal difference between head and eye movements
71
In the dark, what is VOR gain?
-0.9
72
In the dark, what is the VOR phase shift?
0
73
In the light, what is VOR gain?
-1.0
74
Describe torsional VOR
Tilting of the head from shoulder to shoulder
75
What primarily mediates dynamic torsional VOR?
Vertical semicircular canals
76
What is the gain range for dynamic torsional VOR?
-0.4 to -0.7
77
What mediates static torsional VOR?
Otolith-ocular reflex from inputs of the utricles
78
What is the gain range for static torsional VOR?
-0.1 - -0.24
79
How is VOR controlled?
Pure reflex, with an arc of 3 or 4 neurons
80
When the head rotates, which horizontal canal is stimulated (ipsi or contralateral)?
Ipsilateral
81
When the head is rotated to the left, which horizontal canal is stimulated, and which muscles are activated?
Left (ipsilateral) horizontal canal, stimulating the left medial rectus, and the right lateral rectus
82
What is the excitatory pathway of the horizontal VOR neural circuit?
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
What is the inhibitory pathway of the horizontal VOR neural circuit?
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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