Oc Motility > Week 5 > Flashcards

Week 5 Flashcards

(73 cards)

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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
Binocular disparity is dependent on what ratio?
CA/C
26
Binocular disparity is related to what eye movements?
Vergence eye movements
27
What's the 3rd stimulus to accommodation?
Perceptual factors
28
What are the 2 types of perceptual factors?
1. Proximity or size of object | 2. Perspective
29
What's the 4th stimulus to accommodation?
Voluntary effort
30
What are the 6 stimuli to accommodation?
1. Blur 2. Binocular Disparity 3. Perceptual Factors 4. Voluntary effort 5. Miniature Eye movements 6. Chromatic aberration
31
Focusing errors due to ___ ____ serve as a guide for accurate accommodation.
Chromatic Aberration
32
How many diopters does the eye have in chromatic aberration?
1D
33
What are the 5 types of acommodation?
1. Tonic 2. Reflex 3. Proximal 4. Vergence 5. Voluntary
34
Tonic accommodation is due to what?
due to tonus of ciliary muscle
35
Tonic accommodation is a balance between what 2 innervations?
parasympathetic and sympathetic
36
Tonic accommodation manifests when the stimulus is degraded in what conditions?
1. relative darkness 2. empty field 3. total darkness
37
How many diopters of tonic accommodation does the average person have?
0.5-1.5D
38
The posture of the lens in reduced conditions causes what types of myopia?
1. Night myopia | 2. empty field myopia
39
When measured in total darkness, tonic accommodatin is known as what?
Dark focus of accommodation | this is the resting state of accommodation
40
This type of accommodation is induced to obtain clear focus and linked to changes in stimulus distance.
Reflex accommodation
41
Proximal (Psychic) accommodation is induced by what?
induced by the awareness of a near object
42
Vergence accommodation is induced by what? What ratio is it related to?
- induced by vergence changes | - related to CA/C ratio
43
Voluntary accommodation is induced by what?
Induced by effort of will
44
What is amplitude of accommodation?
the maximum motor output of accommodation system
45
Donder's push-up test is affected by:
- Increased target size as object approaches
46
What is the normal diopter lag found in accommodation?
0.75D lag
47
Accom. lead is what 2 factors added together?
tonic accom. + DOF
48
Accom. lag is what 2 factors added together?
Accom. Property + DOF
49
What does soft saturation mean?
Pt only has a little bit of accommodation left
50
What does hard sturation mean?
Pt reached amplitude of accommodation
51
An accurate accommodation response is when...
When the lag of accommodation is small (normal lag ~ +0.25 to +0.75D)
52
What 5 stimulus factors affect accommodation response?
1. High spatial frequency 2. Contrast 3. Luminance 4. Retinal eccentricity 5. Target speed
53
Accommodative response is more accurate between how many cycles/deg?
between 3-10 cycles/deg
54
AR is inaccurate when spatial freq is ?
too high or too low
55
AR is decreased when the stimulation is ____.
peripheral
56
As eccentricity increases, AR ____ dramatically.
decreases
57
If the stimulus doesn't meet the criteria for the 5 stimulus factors that increase Aus?R it's called what?
Reduced stimulus
58
If only tonic accomm. is being used, what type of stimul
Degraded stimulus
59
Can accommodative issues be fixed with VT?
Yes
60
Explain the accommodation after-effect.
Accommodation is stuck at the previous stimulus level due to change
61
With time, can the accommodative after-effect decrease?
Yes, it takes time to return to original baseline level BUT it can become the habitual position of the lens
62
T/F: Prolonged near-point viewing induces prolonged accommodation aftereffect
True
63
Explain accommodative spasm.
Greater than normal accommodative response for a given stimulus demand
64
Accommodative spasm is due to what?
involuntary contraction of the ciliary muscle
65
What are the other 4 names for accommodative mspasm?
1. Accommodative excess 2. Hyperaccommodation 3. Pseudomyopia 4. Ciliary spasm
66
What is the latency for the dynamics of accommodation?
latency = 380 +/- 80 msec entire response ~1 sec
67
Accommodation is more accurate with what type of stimuli?
1. Stationary Stimuli | 2. Slow moving stimuli
68
What is the near triad?
1. Accommodation 2. Converge 3. Miosis
69
What are the 2-way interaction of the near triad?
1. accommodation causes vergence | 2. Convergence causes accommodation
70
Mueller's experiment proved that?
vergence induced is called accommodative vergence
71
How is accommodative vergence measured? What's the ave. prism diopters per diopter?
Measured as AC/A ratio | ~ 3-4 pd per diopter
72
To accommodate, what 2 things do we need?
1. parasympathetic system | 2. EW nucleus
73
Wat do we need to relax accommodation?
Sympathetic system
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