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PART ONE REVISION. > PHYSIOLOGY - Eye movements > Flashcards

PHYSIOLOGY - Eye movements Flashcards

1
Q

What is the difference between uniocular and binocular movements?

A

uniocular movements - duction.
binocular movements - vergence and versions.

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2
Q

What are the six movements of duction? Which axis?

A
  1. ADduction (vertical axis - z axis)
  2. ABduction (vertical axis - z axis)
  3. ELEVATION (horizontal axis - x axis)
  4. Depression (horizontal axis - x axis)
  5. Intorsion (anteroposterior axis/y axis)
  6. Extorsion (anteriorposterior axis/y axis)
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3
Q

What is listing’s plane?

A

x axis and z axis transverse the globe through the equator and form the Listin’gs plane.

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3
Q

What is the difference between versions and vergence eye movements?

A

versions are CONJUGATE synchronous movements in same direction

vergence are DISJUGATE movement of eyes in opposite directions

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4
Q

For the horizontal recti muscles, why do they only have one primary action?

A

Their insertion into the eyeball is straight and vertical and in primary position of gaze, their muscle plane co-incides with the visual axis.

Their movement occurs along the z-axis.

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5
Q

Which muscles are activated in dextroversion?
Which muscles are activated in levoversion?

A

dextro: right LR, left MR
levo: left LR, right MR

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6
Q

at what angle of the globe do the visual and orbital axis co-incide for the vertical recti muscles? Why?
Which muscle action occurs in this plane?

A

When globe is ABducted at 23 degrees, the visual and orbital axis co-incide allowing primary action of elevation or depression.

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7
Q

When the globe is aDducted at 67 degrees, what happens to the visual and orbital axis? What movements can occur here for vertical recti muscles?

A

the visual and orbital axis are at 90 degrees to each other of vertical recti muscles. This causes rotational movements.
SR - INTORSION
IR - EXTORSION

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8
Q

In which gaze is the optimal position of globe for testing the function of vertical recti muscles?

A

ABduction - visual and orbital axis co-incide here.

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9
Q

What are the actions of the vertical recti muscles?

A

SR: elevation, intortion, adduction
IR: depression, extortion, adduction.

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10
Q

What is the globe angle to allow the visual and orbital axis to co-incide for the OBLIQUES? What action of movement occurs here?

A

51 degrees ADduction.
IO: elevation
SO: depression.

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11
Q

What is the globe angle to allow visual and orbital axes to be 90 degrees from each other? What action of movement occurs here?

A

39 degrees ABduction.
IO: extorsion
SO: intorsion.

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12
Q

What is the optimal position for globe testing for the function of the obliques muscles?

A

ADduction. (visual and orbital axis co-incide)

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13
Q

What are the actions of the obliques?

A

SO: intorsion, depression, abduction
IO: extorsion, elevation, abduction

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14
Q

What are the muscles acting in elevation?

What are the muscles acting in depression?

A
  1. bilateral SR and bilateral IO.
  2. bilateral IR and bilateral SO
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15
Q

What muscles cause dextroelevation?

A
  1. RIGHT SR (in abduction, SR moves eye upwards)
  2. LEFT IO (in adduction, IO moves eye upwards)
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16
Q

What muscles cause levodepression?

A
  1. Left IR (in abduction, IR moves eye downwards)
  2. Right SO (in adduction, SO moves eye downwards)
17
Q

Which muscles cause dextrocycloversion?

A

Right eye extorsion, Left eye intorsion.
1. Right IO (extorsion)
2. Left SO (intorsion)

18
Q

Which muscles cause levocycloversion?

A

Left eye extorsion, Right eye intorsion.
1. Left IO (extorsion)
2. Right SO (intorsion)

19
Q

Which muscles are involved in con-vergence?

A

RIght and Left medial rectus.

20
Q

Which muscles are involved in di-vergence?

A

Right and left lateral rectus

21
Q

What is the primary position of gaze?

A

position assumed by eye when fixing at distant object with head erect.

22
Q

What are the secondary positions of gaze? (3)

A

Elevation, Depression, Right and Left.

23
Q

What are the tertiary positions of gaze?

A

dextroelevation, dextrodepression, levoelevation and levodepression.

24
Q

What are the six cardinal positions of gaze?

A

position in which each fo the 12 EOM can be tested individually in their main field of action

25
Q

complete the diagram for testing muscles.

A
26
Q

Superior muscles ……tort
Inferior muscles …..tort

Obliques act in … duction
Obliques tertiary action is … duction

Recti act in …. duction
Recti tertiary action is …. duction

A

Superior muscles INtort
Inferior muscles EXtort

Obliques act in ADduction
Obliques tertiary action is ABduction

Recti act in ABduction
Recti tertiary action is ADduction

27
Q

What are the yoke muscle pairs? Complete the diagram.

A
28
Q

What are the cortical centres (cortexes) involved in eye movements? (2)

A
  1. Frontal cortex - voluntary activity
  2. Occipital cortex (and superior colliculus) - co-ordinating centres
29
Q

Which movement is slower, versional movements or vergence movements?

A

vergence

30
Q

What is Donder’s law?

A

The amount of false torsion associated with any tertiary position of gaze is constant, regardless of how the eye achieved that position.

eg the orientation of the eye when looking up and right is the same when the eye reached this position by first rotating right and then up or first up and then right.

“Donder makes the eyes yonder in the same direction

31
Q

What is Hering’s law?

A

during voluntary conjugate eye movements, the extent of movement of one eye is equal and symmetric to the other eye ie. the innervation to yoke muscle pairs are equal.

HERING HELPS THE TEAM - both eyes work together with equal stimulation.

32
Q

What is Sherrington’s law?

A

Increased contraction of the prime mover EOM is associated with diminished contractile activity of the antagonist muscle

SHERRINGTON STOPS THE SIDEKICK - One muscle works, the other relaxes in same eye.

33
Q

What is the initiation of eye movements controlled by?

A

The vermis

34
Q

What are smooth pursuit movements and what are they controlled by?

A

smooth, continuous tracking movements to keep an object on the fovea.

Controlled by ipsilateral occipitoparietal region (supranuclear cortical control)

35
Q

What is the velocity and latency of smooth pursuit movements?

What is the velocity and latency of saccadic movements?

A

Smooth pursuit:
velocity - 30-50 degrees per second
latency - 150ms

Saccadic movements
velocity - 800-1000 degrees per second
latency - 150ms

36
Q

what’s the difference between smooth pursuit movements and saccadic movements?

A

smooth pursuit aims to keep object in the fovea, VA doesn’t change, saccadic movements aim to place object in the peripheral field onto the fovea, VA is reduced.

37
Q

What are saccadic movements controlled by?
Which part controls horizontal saccades?
Which part controls vertical saccades?

A

contralateral frontal cortex (supranuclear cortical control)

Horizontal saccades - Pons
Vertical saccades - Mid-brain

38
Q

What is optokinetic nystagmus?

A

staionary observer and moving scene or moving scene and stationary observer.

Has slow phase (smooth pursuit) when eye follows target and fast flick (saccadic) when readjust to new target position.

39
Q

What does defective optokinetic nystagmus indicate?

A

cerebral cortex lesion

PART ONE REVISION. (78 decks)

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