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Vision Science 5 > Lecture 14 Objectives > Flashcards

Lecture 14 Objectives Flashcards

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1
Q

What are the three types of fixational eye movements?

A

Microtremor
Microsaccades
Microdrift

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2
Q

What is the amplitude of microtremors?

A

5-30 minutes of arc

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3
Q

Which is smaller, microsaccades or microtremors?

A

Microtremors

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4
Q

What is the frequency of microtremors?

A

50-100 Hz

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5
Q

What is the mean amplitude of microsaccades?

A

6 minutes of arc

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6
Q

T or F: The amplitude of microsaccades is usually less than 26 minutes of arc.

A

True

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7
Q

T or F: Microtremors are low frequency and high amplitude.

A

False - high frequency and low amplitude

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8
Q

What is the frequency of microsaccades?

A

120 Hz

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9
Q

What is the purpose of microdroft?

A

To prevent the image of a stable object from drifting off the retina

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10
Q

What is the velocity of microdrift?

A

less than 20 minutes of arc per second

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11
Q

Which of the fixational eye movement have no known function?

A

Microsaccades

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12
Q

What are the four types of fixation anomalies?

A

Anomalous slow drift
Saccadic intrusions
Saccadic oscillations
Nystagmus

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13
Q

What is the magnitude of anomalous slow drift?

A

1 degree or more

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14
Q

What is the most common cause of anomalous slow drift?

A

Amblyopia

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15
Q

Many conditions involving the ___ may cause anomalous slow drift.

A

Fovea

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16
Q

What is the definition of saccadic intrusions?

A

Sporadic, biphasic disruptions of fixation

17
Q

The frequency of normal saccadic intrusions increases with ___.

A

Age

18
Q

A normal saccadic intrusion shows a square wave jerk movement with an amplitude of what?

A

0.5-3 degrees

19
Q

What is the amplitude of a macro-square wave jerk movement?

A

4-50 degrees

20
Q

Saccadic intrusions are associated with what?

A

Cerebellar or brainstem diseases

21
Q

What are saccadic oscillations?

A

Continuous disruptions of fixation

22
Q

What are the two types of saccadic oscillations?

A

Macrosaccadic oscillation

Opsoclonus

23
Q

What are macrosaccadic oscillations?

A

A series of large saccades that straddle fixation, but never fixate correctly

24
Q

Patients with macrosaccadic oscillations can’t make which type of saccade?

A

Commanded (voluntary) saccade

25
Q

What is opsoclonus?

A

A saccadic oscillation without an intersaccadic interval

26
Q

Which type of saccadic oscillation doesn’t demonstrate a square wave jerk?

A

Opsoclonus

27
Q

What are the two types of nystagmus?

A

Jerk nystagmus

Pendular nystagmus

28
Q

Which type of nystagmus is the most typical?

A

Jerk nystagmus

29
Q

Describe jerk nystagmus.

A

Rhythmic oscillations containing a slow phase

30
Q

What is the magnitude of jerk nystagmus?

A

Up to 10 degrees

31
Q

What is the rate of jerk nystagmus?

A

Up to 8 Hz

32
Q

What is pendular nystagmus?

A

To and fro movements without any slow phase`

33
Q

Which type of nystagmus is usually congenital?

A

Pendular

Vision Science 5 (8 decks)

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