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Fall17-OcularMotility > Block 1 > Flashcards

Block 1 Flashcards

1
Q

What is positive angle lambda mean?

A

In hirschberg, it means the eye is exo

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2
Q

What is negative angle lambda?

A

Eye is eso

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3
Q

What is the motor system responsible for in vision?

A

It enlarges the field of view to make it a field of fixation

Brings image to fovea and keeps it there

Gives best single binocular vision by aligning the eyes

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4
Q

The action of a muscle is due to what?

A

The direction of it’s pull

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5
Q

This is the point at the center of the muscle or tendon that first touches the globe

A

Tangential point

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6
Q

This is the arc formed between the tangential point and the center of insertion of the muscle on the sclera. It changes length as contraction and relaxation occurs

A

Arc of contact

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7
Q

This is the direction of the pull of the muscle and determines the axis the muscle will move around?

A

Muscle plane

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8
Q

What is the order of the spiral of Tillaux from shortest to longest?

A

Medial rectus
Inferior rectus
Lateral rectus
Superior rectus

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9
Q

How far is the medial rectus from limbus?

A

5.5mm

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10
Q

How far is the inferior rectus from the limbus?

A

6.5

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11
Q

How far is the lateral rectus from the limbus?

A

6.9mm

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12
Q

How far is the superior rectus from the limbus?

A

7.7mm

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13
Q

Which axis do the horizontal rectus muscles move on?

A

Z

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14
Q

Which axis do the vertical rectus muscles move on?

A

X

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15
Q

What is the primary action of the medial rectus?

A

Adduction

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16
Q

What is the primary action of the lateral rectus?

A

Abduction

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17
Q

What is the primary action of the superior rectus?

Secondary action?

Tertiary action?

A

Elevation

Intortion

Adduction

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18
Q

What is the primary action of inferior rectus?

Secondary?

Tertiary?

A

Depression

Extortion

Adduction

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19
Q

What is the primary action of the superior oblique?

Secondary?

Tertiary?

A

Intorsion

Depression

Abduction

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20
Q

What is the primary action of the inferior oblique?

Secondary?

Tertiary?

A

Extortion

Elevation

Abduction

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21
Q

At what degree and which direction do the visual and orbital axes coincide and the superior rectus acts ONLY as an elevator?

A

23 degrees abducted

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22
Q

At what angle do the oblique muscles insert into the globe?

A

51 degrees

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23
Q

At what angle and direction does the superior oblique act only as an intorter?

A

ABducted 39 degrees

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24
Q

At what angle and direction is the superior oblique only a depressor?

A

Adducted 51 degrees

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25
Q

This is the position when eyes are fixating straight ahead. The eyes and head are both straight.

A

Primary position

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26
Q

This is when the eyes are purely moving vertically or horizontally

A

Secondary position

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27
Q

This is the Y axis movement - including head tilt positions

A

Tertiary position

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28
Q

What are cardinal positions and how many are there?

A

They are when only ONE muscle in each eye is responsible for movement

There are 6

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29
Q

This is the gaze where the effect of a single muscle is best observed (cardinal position)

A

Field of action

30
Q

What direction and degree does the superior rectus become a pure intortor?

A

Adduction 67 degrees

31
Q

Any weakness of the superior oblique will be seen as what?

A

Failure of depression in ADDUCTION

32
Q

This is a pair of muscles in the same eye that move the eye in opposite directions

A

Agonist-antagonist

33
Q

This is a pair of muscles in the same eye that move the eye in the same direction

A

Synergistic muscle

Ex. Inferior oblique and superior rectus

34
Q

This is a pair of muscles, one in each eye, that move the eye in the same direction

A

Yoke muscle

35
Q

This is the law of innervation which increases innervation to one muscle and decreases innervation to its antagonist in the SAME EYE.

A

Sherrington law

This is NOT yoked muscles

36
Q

This law of innervation is equal and simultaneous innervations to yoked muscles

A

Hering law

37
Q

What is primary deviation

A

When the UNaffected eye is fixating

38
Q

What is secondary deviation?

A

When the restricted eye is fixating

Usually bigger than a primary deviation b/c of the increased innervation to get the bad eye to fixate

39
Q

In deviations, the increased innervation goes to which eye to cause an excessive action and larger deviation?

A

NON-fixating eye!!

40
Q

Which muscles are we looking at when patient looks up and to their right?

A

SR and IO

41
Q

Which muscles when patient looks up and to their left?

A

IO and SR

42
Q

When muscles when patient looks down and to their right?

A

IR and SO

43
Q

Which muscles when patient looks down and to their left?

A

SO and IR

44
Q

This is movement of one eye?

A

Suction

45
Q

This is binocular, conjugate movements of the eyes?

A

Version

46
Q

What are vergences important for?

A

Fusion

47
Q

This is how quick the eyes start to follow a target after a stimulus

A

Latency

48
Q

Versions are _____ acting movements which vergences are ______.

A

Fast

Slow

49
Q

What are versions and vergences controlled by?

A

Supra nuclear pathway

50
Q

What does the supranuclear pathway do?

A

Cortex and brainstem. Plans and controls the eye movements

51
Q

These are the fast conjugate eye movements to place and keep images on the fovea

A

Saccades

52
Q

What is saccade latency time?

When is it developed?

A

120-200 ms

Usually developed by 1 year old

53
Q

These are eye movements that maintain a target moving in the parafovea.

This helps match eye velocity to target velocity

A

Pursuits

54
Q

Which LATENCY is faster? Pursuits or saccades

A

Pursuits!!

55
Q

When are smooth pursuits developed?

A

3rd to 4th month

56
Q

When are pursuits involuntary?

A

In Optokinetic movements to track a moving object then refixate with a saccade

57
Q

This is the reflex that stabilizes a retinal image during brief head movement - the head is moving NOT the target.

What is the maneuver to induce this?

A

Vestibulo-ocular reflex (VOR)

Doll’s head

58
Q

When does VOR develope and does it require stimuli?

A

Horizontal VOR is developed at birth, but vertical VOR develops much later

No stimuli required

59
Q

What is the eye movement produced in VOR?

A

They are equal magnitude but opposite in direction to the head movement to keep the target focused

Vestibular damage causes horizontal nystagmus

60
Q

If Doll’s head is not possible, what is another test for VOR?

A

Caloric Testing!

Angle head to 30 degrees and pour water in ear

61
Q

What does warm water produce?

A

A fast eye movement to same ear

COWS

62
Q

This is the continuous eye movements AFTER brief head movements.

It holds image of the world steady on the retina during sustained head movement

A

Optokinetic reflex (OKR)

63
Q

This is a slow pursuit eye movement followed by a fast corrective saccade

A

Optokinetic nystagmus (OKN)

64
Q

What does the OKN require that VOR doesn’t?

A

OKN requires visual input!

65
Q

What is an OKN drum good for?

A

Malingering and uncooperative patients

It means that VA is at or better than size of the stripes

66
Q

These vergences require attention and cooperation of the cerebral cortex - the eyes move to correct the disparity and get images back on the retina

A

Fusional vergences

67
Q

These vergences hold our eyes straight. This is constant innervation when awake and alert

A

Tonic vergence

68
Q

This type of vergence is induced convergence movement due to the awareness of something near

A

Proximal vergence

69
Q

This type of vergence is an increment of accommodative convergence that happens with each diopter of accommodation (AC/A ratio)

A

Accommodative vergence

70
Q

What does abnormally high AC/A produce?

A

Esotropia - too much convergence

71
Q

What does abnormally low AC/A produce?

A

Exotropia - harder to converge

Fall17-OcularMotility (4 decks)

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