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Oc Motility > Week 1 > Flashcards

Week 1 Flashcards

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1
Q

What are the 3 reasons why we need eye movements?

A
  1. To change the angle of gaze
  2. To keep visual images stable on retina
  3. To prevent fading of visual images
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2
Q

What 3 major eye movements hold images steady on the retina, preventing motion smear?

A
  1. Fixation
  2. VOR
  3. OKN
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3
Q

What 3 major eye movements change the angle of gaze by directing the fovea?

A
  1. Saccades
  2. Pursuits
  3. Vergence
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4
Q

WIT: Eyes continue to fixate on target as head moves.

A

Vestibular Ocular Reflex

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5
Q

WIT: Eyes fixate on a moving target while head is still

A

Optokinetic Nystagmus

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6
Q

Stabilization of the angle of gaze is accomplished by what 2 eye movements?

A

VOR and OKN

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7
Q

What are the 3 mini movements prevent fading of visual images??

A
  1. drifts
  2. tremors
  3. saccades
  • velocity is less than 1 degree per sec
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8
Q

Explain the Troxler Effect

A

Fading of stabilized retinal image

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9
Q

What 3 things are required for eye movements?

A
  1. The orbital plant
  2. EOMs
  3. Neural Network
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10
Q

What 2 forces must the eye overcome to move?

A
  1. Viscous drag of orbit

2. Elastic restoring forces of orbital tissues

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11
Q

WIT: Burst in neural activity to allow the EOM to move quickly, saccade

A

Pulse

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12
Q

WIT: Keeps the eye in position and holds it against elastic restoring forces

A

Step

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13
Q

What happens in a faulty pulse?

A

Eye movement is too slow; looks more like pursuit

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14
Q

What happens ina faulty step?

A

Eccentric eye position cannot be maintained

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15
Q

At what age does VOR develop?

A

6 months in utero (first one to develop)

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16
Q

When does OKN develop?

A

at birth

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17
Q

When does Saccades develop?

A

newborn

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18
Q

When will pursuits develop?

A

6-8 weeks

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19
Q

When does vergence,,

accommodation and binocularity develop?

A

at 3 months

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20
Q

WIT: The brain needs information about where the eye is located w/ respect to the head/orbit?

A

Afferent System - sends sensory information to the brain

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21
Q

WIT: The brain needs information regarding where and by how much to move the eye?

A

Efferent System - outgoing information from the brain to the eyes

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22
Q

What are the 2 sources of afferent information?

A

Proprioception

Efferency copy/Corollary discharge

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23
Q

What 2 things does proprioception include to aid in the afferent system?

A
  1. Muscle spindles - in EOMs, respond to stress

Palisade Tendon Organ - in EOMs, responds to tension

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24
Q

WIT: A copy of the efferent response to move the eyes is sent back to a different part of the brain for instant knowledge of eye location

A

Efference Copy

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25
Pulse and step signals are apart of what system?
Efferent System - tells the eyes where and how much to move
26
WIT: global fibers, good for rapidly moving the eye to a new position?
Twitch fibers (burst)
27
WIT: orbital fibers, good for maintaining new eye position
Non-twitch fibers (tonic/step)
28
WIT: elevation and depression axis
X-axis
29
WIT: Abduction and adduction axis
Z-axis
30
WIT" Intorsion and Extorsion
Y-axis
31
WIT: Superior Pole moves nasally
Intorsion
32
WIT: Superior POle moves temporally
Extorsion
33
All possible points go through what point inside the globe?
Semicircular locus or Space Centroid or Body Centroid
34
Who's Law is This: Law depends on the horiontal and vertical gaze angles to get to a tertiary movement
Donder's Law
35
Who's Law: Rotation about an axis on Listing's plane ; causes the eye to move to another position in one movement
Listing's Law
36
WIT: Define the limit of eye rotation (i.e. field of fixation); formed by Tenon's capsule
Check ligament
37
WIT: Superior Check ligament
CL of Whitnall
38
WIT: Inferior Check Ligament
CL of Lockwood
39
WIT: Defined by lines joining the center of rotation to the muscle axis
Muscle Plane
40
WIT: Physical point of insertion of the EOM to the eyeball
Anatomical Insertion
41
WIT: The point on the muscle that is tangential to the eye/globe; where the belly touches
Physiological Insertion
42
Superior muscles ____
intort
43
Inferior muscles _____
extort
44
Vertical recti ______
adduct
45
Oblique muscles _____
abduct
46
Who's Law: Increased activity in one EOM (agonist) is associated with decreased activity in the antogonist EOM (in same eye)
Sherrington's law
47
Who's Law: Equal and simultaneous innervation is given to synertistic EOMs (yoked muscles in opposite eye)
Hering's Law
48
Eye rotations occur alone with small < ___ degree movements. Anything over that, eye and head rotate together.
15 degree
49
Monocular field of fixation is limited by the _______.
Orbital Plant
50
Binocular field of fixation is limited by the ability to maintain ____ fixation
Bi-foveal fixation
51
What are the 3 things must a target be for a clinical exam?
1. Interesting 2. Challenging 3. Accomodation
52
CN3 Palsy results in what 3 things?
1. Dilated pupil 2. Ptosis 3 Strabismus (down & out)
53
CN6 palsy results in what deficit?
Abduction deficit
54
What test can you do to determine if a CN4 palsy is there?
Parks 3-step test
55
What are the 3 steps of Parks 3-step?
Step 1: Primary gaze Step 2: L & R gaze Step 3: L & R head tilt
56
WIT: An eye movement generated to follow or track a moving target
Pursuits
57
What is the pursuit latency?
10-150 msec
58
What is the VOR latency?
16 msec
59
What is the OKN latency?
70msec
60
What is saccade latency?
200msec
61
What are the stimuli for pursuits?
1. Visual Targets 2. Non- visual targets 3. Imaginary targets
62
What are the 2 types of non-visual stimuli?
Auditory and Tactile stimulus
63
In photopic conditions, the ____ is used to track targets. In scotopic conditions the ____ is used to track targets
Fovea, parafovea
64
Can a patient w/ AMD pursue a moving target? experience OKN or VOR
Yes, but may not be accurate Yes, Yes
65
What are the 3 functions of pursuits?
1. stabilizes images of small moving target on fovea 2. VOR cancellation 3. OKN cancellation
66
What is the gain (eye velocity/head velocity) of Pursuits?
1.0 (ideal)
67
Does a pursuit rely more on where the target is or how fast the target is moving?
Both
68
This is caused whena pursuit target is moving too fast or in an unpredictable path
Saccadic Intrusion Back-up saccades correct these movements
69
What 3 things occur when you have bad pursuits?
1. visual smearing 2. blurred vision 3. saccadic intrusion
70
What are the horizontal movement neural integrators?
1. Medial Vestibular Nucleus | 2. Nucleus Prepositus Hypoglossi
71
What is the vertical and torsional neural integrators?
Interstitial Nucleus of Cajal (INC)

Oc Motility (10 decks)

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