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Oc Motility > Week 5 > Flashcards

Week 5 Flashcards

1
Q

What’s the most important structure for horizontal gaze found in the tegmentum of Pons?

A

Abducen’s Nucleus

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2
Q

What 2 group of neurons does the abducens nucleus contain?

A
  1. Motor Neurons

2. Internuclear Neurons

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3
Q

Motor neurons of the abducens nerve do what?

A

send axons to innervate the ipsilateral lateral rectus

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4
Q

Internuclear nuerons of the abducens nerve do what?

A

Project to the contralateral MLF to synapse on the contralateral medial rectus

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5
Q

What are the 4 subpopulations of neurons in the abducens nerve?

A
  1. Twitch
  2. Non-twitch
  3. Internuclear
  4. Paramedian Tracts
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6
Q

The abducens nucleus receives input for what 3 things?

A
  1. Horizontal saccades from PPRF
  2. VOR, OKN, & Pursuits
  3. Step signals from NPH and MVN
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7
Q

Lesions of the left abducens nucleus cause what ? What else is effected?

A

Left Horizontal conjugate gaze palsy

  • Impaired right VOR
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8
Q

What 2 things are unaffected in a horizontal conjugate gaze center?

A
  1. Vergence

2. Vertical Movements

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9
Q

Lesions of the MLF cause what eye disorder?

A

Internuclear Ophthalmoplegia (INO)

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10
Q

INO is named by the eye with the _____ deficit.

A

adduction

- right eye can’t adduct, right INO

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11
Q

What type of nystagmus develops from INO?

A

Dissociated Nystagmus

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12
Q

When someone has one and a half syndrome, what does this mean?

A
  1. Impaired conjugate gaze to one side

2. Impaired adduction on opposite side

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13
Q

What’s the only surviving horizontal conjugate movement in one and a half syndrome?

A

Abduction of contralateral eye

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14
Q

Is convergence affected in one and a half syndrome?

A

No. convergence is unaffected

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15
Q

Where are the possible lesions for one and a half syndrome?

A
  1. Combined abducens nucleus and adjacent MLF

2. Bilateral INO and unilateral abducens palsy

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16
Q

Lesion of MLF leads to what issue?

A

INO

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17
Q

Oculomotor and trochlear nuclei receive inputs for vertical saccades from what?

A

riMLF

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18
Q

The interstitial nucleus of cajal provides what type of signals?

A

Step signals

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19
Q

The cerebellum does what?

A

Ensures all eye movements and gaze holding are calibrated to provide clearest vision

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20
Q

The cerebellum contains what 3 things?

A
  1. Vestibulo-cerebellum
  2. Dorsal Vermis
  3. Fastigial Nucleus
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21
Q

The vestibulo-cerebellum consists of what 4 things?

A
  1. Flocculus
  2. Paraflocculus
  3. Nodulus
  4. Ventral Uvula
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22
Q

What 3 things is the vestibulo-cerebellum important for?

A
  1. Steady gaze holding
  2. Smooth pursuits
  3. Optimal VOR
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23
Q

What is the stimulus to accommodation?

A

Blur

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24
Q

What is the 2nd stimulus to accommodation?

A

Binocular Disparity

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25
Q

Binocular disparity is dependent on what ratio?

A

CA/C

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26
Q

Binocular disparity is related to what eye movements?

A

Vergence eye movements

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27
Q

What’s the 3rd stimulus to accommodation?

A

Perceptual factors

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28
Q

What are the 2 types of perceptual factors?

A
  1. Proximity or size of object

2. Perspective

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29
Q

What’s the 4th stimulus to accommodation?

A

Voluntary effort

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30
Q

What are the 6 stimuli to accommodation?

A
  1. Blur
  2. Binocular Disparity
  3. Perceptual Factors
  4. Voluntary effort
  5. Miniature Eye movements
  6. Chromatic aberration
31
Q

Focusing errors due to ___ ____ serve as a guide for accurate accommodation.

A

Chromatic Aberration

32
Q

How many diopters does the eye have in chromatic aberration?

A

1D

33
Q

What are the 5 types of acommodation?

A
  1. Tonic
  2. Reflex
  3. Proximal
  4. Vergence
  5. Voluntary
34
Q

Tonic accommodation is due to what?

A

due to tonus of ciliary muscle

35
Q

Tonic accommodation is a balance between what 2 innervations?

A

parasympathetic and sympathetic

36
Q

Tonic accommodation manifests when the stimulus is degraded in what conditions?

A
  1. relative darkness
  2. empty field
  3. total darkness
37
Q

How many diopters of tonic accommodation does the average person have?

A

0.5-1.5D

38
Q

The posture of the lens in reduced conditions causes what types of myopia?

A
  1. Night myopia

2. empty field myopia

39
Q

When measured in total darkness, tonic accommodatin is known as what?

A

Dark focus of accommodation

this is the resting state of accommodation

40
Q

This type of accommodation is induced to obtain clear focus and linked to changes in stimulus distance.

A

Reflex accommodation

41
Q

Proximal (Psychic) accommodation is induced by what?

A

induced by the awareness of a near object

42
Q

Vergence accommodation is induced by what? What ratio is it related to?

A
  • induced by vergence changes

- related to CA/C ratio

43
Q

Voluntary accommodation is induced by what?

A

Induced by effort of will

44
Q

What is amplitude of accommodation?

A

the maximum motor output of accommodation system

45
Q

Donder’s push-up test is affected by:

A
  • Increased target size as object approaches
46
Q

What is the normal diopter lag found in accommodation?

A

0.75D lag

47
Q

Accom. lead is what 2 factors added together?

A

tonic accom. + DOF

48
Q

Accom. lag is what 2 factors added together?

A

Accom. Property + DOF

49
Q

What does soft saturation mean?

A

Pt only has a little bit of accommodation left

50
Q

What does hard sturation mean?

A

Pt reached amplitude of accommodation

51
Q

An accurate accommodation response is when…

A

When the lag of accommodation is small (normal lag ~ +0.25 to +0.75D)

52
Q

What 5 stimulus factors affect accommodation response?

A
  1. High spatial frequency
  2. Contrast
  3. Luminance
  4. Retinal eccentricity
  5. Target speed
53
Q

Accommodative response is more accurate between how many cycles/deg?

A

between 3-10 cycles/deg

54
Q

AR is inaccurate when spatial freq is ?

A

too high or too low

55
Q

AR is decreased when the stimulation is ____.

A

peripheral

56
Q

As eccentricity increases, AR ____ dramatically.

A

decreases

57
Q

If the stimulus doesn’t meet the criteria for the 5 stimulus factors that increase Aus?R it’s called what?

A

Reduced stimulus

58
Q

If only tonic accomm. is being used, what type of stimul

A

Degraded stimulus

59
Q

Can accommodative issues be fixed with VT?

A

Yes

60
Q

Explain the accommodation after-effect.

A

Accommodation is stuck at the previous stimulus level due to change

61
Q

With time, can the accommodative after-effect decrease?

A

Yes, it takes time to return to original baseline level BUT it can become the habitual position of the lens

62
Q

T/F: Prolonged near-point viewing induces prolonged accommodation aftereffect

A

True

63
Q

Explain accommodative spasm.

A

Greater than normal accommodative response for a given stimulus demand

64
Q

Accommodative spasm is due to what?

A

involuntary contraction of the ciliary muscle

65
Q

What are the other 4 names for accommodative mspasm?

A
  1. Accommodative excess
  2. Hyperaccommodation
  3. Pseudomyopia
  4. Ciliary spasm
66
Q

What is the latency for the dynamics of accommodation?

A

latency = 380 +/- 80 msec

entire response ~1 sec

67
Q

Accommodation is more accurate with what type of stimuli?

A
  1. Stationary Stimuli

2. Slow moving stimuli

68
Q

What is the near triad?

A
  1. Accommodation
  2. Converge
  3. Miosis
69
Q

What are the 2-way interaction of the near triad?

A
  1. accommodation causes vergence

2. Convergence causes accommodation

70
Q

Mueller’s experiment proved that?

A

vergence induced is called accommodative vergence

71
Q

How is accommodative vergence measured?

What’s the ave. prism diopters per diopter?

A

Measured as AC/A ratio

~ 3-4 pd per diopter

72
Q

To accommodate, what 2 things do we need?

A
  1. parasympathetic system

2. EW nucleus

73
Q

Wat do we need to relax accommodation?

A

Sympathetic system

Oc Motility (10 decks)

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