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OP2204- Optometric Neurophysiology Lectures > 8. Eye Movements 1 & 2 > Flashcards

8. Eye Movements 1 & 2 Flashcards

1
Q

Eye movement is the movement of?

A

Movement of the brain itself because the eye is not a peripheral organ.

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2
Q

Retina is what type of tissue?

A

Brain tissue

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3
Q

Do eye muscles have monosynaptic strech reflex?

A

No

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4
Q

What does each movement have in unique?

A

Each EM has its own function, stimulus, anatomic & physiological pathway.
Also, this movements can occur simultaneously at the same time.

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5
Q

What is saccade?

A

The fastest eye movement that can be made. Hence, to record saccades a high sampling rate is required.

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6
Q

Eyes have how many muscles?

A

6 muscles that exists in pairs.

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7
Q

How many axis for eye movements?

A

3 axes
1. Vertical axis- movement of eyes horizontally.
2. Horizontal axis- movement of eyes vertically.
3. Visual axis- along the fovea at the centre of the pupil, controls torsion of the eye.

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8
Q

2 overall functions of eye movements?

A
  1. Maintain a stable view of the world
  2. Redirect the line of sight
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9
Q

What are the 2 compensatory (Reflective eye movements)? And the role of this movements?

A

VOK & OKN
Role: correct eye movements to keep the view stable

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10
Q

Saccades meaning?

A

Change in gaze independent to head orientation.

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11
Q

Smooth pursuit movement?

A

Follow a (Slowly) moving target.

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12
Q

Vergence meaning?

A

Enlarge binocular field/ reduce disparity.

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13
Q

3 eye movements that redirect line of sight (Fovea)

A

Saccades, smooth pursuit & vergence

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14
Q

Vergence is said to be the only disjunctive eye movement, what does this mean?

A

eyes move in opposite directions

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15
Q

Effect of inertial mass on eye movements humans vs birds

A

Humans have a smaller inertial mass of eyes compared to birds. Hence, in birds the head moves to create movements whereas in humans eyes move.

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16
Q

Primates have frontally faced eyes but animals have laterally orientated eye, hence they require a special system to main stable gaze. what is the special system for birds?

A

Head bobbing in birds

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17
Q

Influence of eye movements?

A

Disturbance to the stable view of the world

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18
Q

Land’s observation?

A

All animals have the same five visuomotor movements.

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19
Q

Mittelstaedt’s hypothesis?

A

Saccadic systems are designed to localize objects in space.

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20
Q

Most eye movements are conjugate- what does this mean?

A

Eyes moves together

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21
Q

What is the relationship between head movements?

A

Gaze

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22
Q

Stability of vision is the same as stability of gaze- what does this mean?

A

This is the stability gaze that is stability of retinal image on the fovea

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23
Q

3 Classifications of eye movements?

A
  1. Compensatory/ stabilizing OR targeting.
  2. Conjugate or disjunctive
  3. Visual vs non- visual stimulus (VOR)
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24
Q

2 Compensating eye movements?

A

VOR - Vestibulo-ocular reflex
OKN- Optokinetic Nystagmus

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25
Q

3 Targeting movements?

A

Saccades, Smooth Pursuit and Vergence

26
Q

Which eye movement has no visual stimulus?

A

VOR

27
Q

Role of VOR

A

Stabilises gaze ensuring clear vision during head movements. It is non-visual stimulus

28
Q

Non-visual stimulus is driven by?

A

Afferent signals from the inner ear canals.

29
Q

VOR compensates for?

A

fast, transient head movements

30
Q

VOR takes place in what light conditions?

A

Dark and light

31
Q

Which system kicks in when trying to maintain a stable gaze?

A

VOR

32
Q

VOR is unconscious or conscious?

A

Unconscious

33
Q

VOR driven by which system?

A

Vestibulo system

34
Q

VOR nystagmus meaning

A

The eyes are trying to maintain stable gaze for as long as possible THEN it snaps- this is called slow & fast phase.

35
Q

What is the fastest movement made in terms of latency?

A

VOR

36
Q

Implications of large head movements and fast movements?

A

Large head movements, beyond limit leads to fast phase correction.
Fast movements cause retinal slip- Because VOR IS not compensating for complete head movements.

37
Q

Slow vs fast phase eye movements in relation to head movements?

A

Slow phase: opposite direction to head movement.
Fast phase: same direction to head movements.

38
Q

OKN Role?

A

Stabilizes gaze ensuring clear vision during movements of the visual field (world).

39
Q

Visual stimulus of OKN?

A

Retinal slip or Optic flow

40
Q

OKN compensates for?

A

Fat and transient movements

41
Q

OKN has a speed limit?

A

Yes
OKN can not compensate for very very fast motion

42
Q

OKN generates slow phase movements in which direction?

A

Slow phase movements generated in the same direction and velocity as perceived retinal slip.

43
Q

When OKN reaches its maximum limit it produces?

A

Quick “reset” phase called saccade

44
Q

Saccades or Pursuits - which movement needs a stimulus?

A

Saccades do not require a stimulus. They can also be made from memory. Pursuit needs a stimulus.

45
Q

Ballistic movement?

A

React to 1 stimulus at a time, then a refractive period (i.e., latency period).

46
Q

Main sequence?

A

Correlation between amplitude, duration and velocity. This sequence is used to compare normal Px’s with abnormal Px’s.

47
Q

Saccadic suppression?

A

Inability to see anything during a saccade.

48
Q

When a saccade is executed there is suppression of?

A

Conscious vision in V1

49
Q

Relation between duration and amplitude of saccade?

A

Linear relationship

50
Q

Relationship between peak velocity and saccadic amplitude exists because?

A

Because of action potential of motor neurons driving the muscles making the saccade.

51
Q

Duration and velocity of a saccade is driven by?

A

Duration- bust of firing in the motor neuron
Velocity- by the frequency of action potential

52
Q

Saccadic suppression is suppression of?

A

Low spatial frequency

53
Q

Saccadic suppression involves which pathway?

A

Magnocellular at LGN

54
Q

Which system is suppressed in smooth pursuit?

A

OKN

55
Q

Smooth pursuit is driven by?

A

vestibular NUCLEUS

56
Q

Slowest eye movement is?

A

Vergence

57
Q

How can the speed of vergence be increased

A

If combined with saccades

58
Q

Stimuli for vergence?

A

-Blur = accommodative vergence (provoked by changing lens)
-Disparity = fusional vergence (provoked by changing prism)

59
Q

Retinal ques that provoke accommodative response?

A

Objects temporal to the fovea- interpreted as closer, nasal to the fovea- interpreted as far.

60
Q

Parallax is?

A

Non-retinal que on distance of objects

61
Q

Visuomotor control is restricted by how many axes?

A

3

62
Q

How does the brain identify if change in retinal image is due to objective motion or subjective motion?

A

Brain has a system called efference control center. The brain gets a copy of efference output which is compared against retinal shift.

OP2204- Optometric Neurophysiology Lectures (8 decks)

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