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Oc Motility > Week 1 > Flashcards

Week 1 Flashcards

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
Q

Pulse and step signals are apart of what system?

A

Efferent System - tells the eyes where and how much to move

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26
Q

WIT: global fibers, good for rapidly moving the eye to a new position?

A

Twitch fibers (burst)

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27
Q

WIT: orbital fibers, good for maintaining new eye position

A

Non-twitch fibers (tonic/step)

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28
Q

WIT: elevation and depression axis

A

X-axis

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29
Q

WIT: Abduction and adduction axis

A

Z-axis

30
Q

WIT” Intorsion and Extorsion

A

Y-axis

31
Q

WIT: Superior Pole moves nasally

A

Intorsion

32
Q

WIT: Superior POle moves temporally

A

Extorsion

33
Q

All possible points go through what point inside the globe?

A

Semicircular locus or Space Centroid or Body Centroid

34
Q

Who’s Law is This: Law depends on the horiontal and vertical gaze angles to get to a tertiary movement

A

Donder’s Law

35
Q

Who’s Law: Rotation about an axis on Listing’s plane ; causes the eye to move to another position in one movement

A

Listing’s Law

36
Q

WIT: Define the limit of eye rotation (i.e. field of fixation); formed by Tenon’s capsule

A

Check ligament

37
Q

WIT: Superior Check ligament

A

CL of Whitnall

38
Q

WIT: Inferior Check Ligament

A

CL of Lockwood

39
Q

WIT: Defined by lines joining the center of rotation to the muscle axis

A

Muscle Plane

40
Q

WIT: Physical point of insertion of the EOM to the eyeball

A

Anatomical Insertion

41
Q

WIT: The point on the muscle that is tangential to the eye/globe; where the belly touches

A

Physiological Insertion

42
Q

Superior muscles ____

A

intort

43
Q

Inferior muscles _____

A

extort

44
Q

Vertical recti ______

A

adduct

45
Q

Oblique muscles _____

A

abduct

46
Q

Who’s Law: Increased activity in one EOM (agonist) is associated with decreased activity in the antogonist EOM (in same eye)

A

Sherrington’s law

47
Q

Who’s Law: Equal and simultaneous innervation is given to synertistic EOMs (yoked muscles in opposite eye)

A

Hering’s Law

48
Q

Eye rotations occur alone with small < ___ degree movements. Anything over that, eye and head rotate together.

A

15 degree

49
Q

Monocular field of fixation is limited by the _______.

A

Orbital Plant

50
Q

Binocular field of fixation is limited by the ability to maintain ____ fixation

A

Bi-foveal fixation

51
Q

What are the 3 things must a target be for a clinical exam?

A
  1. Interesting
  2. Challenging
  3. Accomodation
52
Q

CN3 Palsy results in what 3 things?

A
  1. Dilated pupil
  2. Ptosis
    3 Strabismus (down & out)
53
Q

CN6 palsy results in what deficit?

A

Abduction deficit

54
Q

What test can you do to determine if a CN4 palsy is there?

A

Parks 3-step test

55
Q

What are the 3 steps of Parks 3-step?

A

Step 1: Primary gaze
Step 2: L & R gaze
Step 3: L & R head tilt

56
Q

WIT: An eye movement generated to follow or track a moving target

A

Pursuits

57
Q

What is the pursuit latency?

A

10-150 msec

58
Q

What is the VOR latency?

A

16 msec

59
Q

What is the OKN latency?

A

70msec

60
Q

What is saccade latency?

A

200msec

61
Q

What are the stimuli for pursuits?

A
  1. Visual Targets
  2. Non- visual targets
  3. Imaginary targets
62
Q

What are the 2 types of non-visual stimuli?

A

Auditory and Tactile stimulus

63
Q

In photopic conditions, the ____ is used to track targets. In scotopic conditions the ____ is used to track targets

A

Fovea, parafovea

64
Q

Can a patient w/ AMD pursue a moving target? experience OKN or VOR

A

Yes, but may not be accurate

Yes, Yes

65
Q

What are the 3 functions of pursuits?

A
  1. stabilizes images of small moving target on fovea
  2. VOR cancellation
  3. OKN cancellation
66
Q

What is the gain (eye velocity/head velocity) of Pursuits?

A

1.0 (ideal)

67
Q

Does a pursuit rely more on where the target is or how fast the target is moving?

A

Both

68
Q

This is caused whena pursuit target is moving too fast or in an unpredictable path

A

Saccadic Intrusion

Back-up saccades correct these movements

69
Q

What 3 things occur when you have bad pursuits?

A
  1. visual smearing
  2. blurred vision
  3. saccadic intrusion
70
Q

What are the horizontal movement neural integrators?

A
  1. Medial Vestibular Nucleus

2. Nucleus Prepositus Hypoglossi

71
Q

What is the vertical and torsional neural integrators?

A

Interstitial Nucleus of Cajal (INC)

Oc Motility (10 decks)

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