Optokinetic Response and Pursuits (M2) Flashcards Preview

III. Binocular Vision > Optokinetic Response and Pursuits (M2) > Flashcards

Flashcards in Optokinetic Response and Pursuits (M2) Deck (19):
1

What type of eye movement is the optokinetic response?

gaze holding eye movement

2

What effect does blur have on the OKN response? 1 . What is the OKN useful for? 2

1. little to no effect
2. malingering, infants, IDD patients

3

When the OKN is a left beating nystagmus, are the stripes moving to the right or left?

right

4

How can OKN be used to estimate VA?

decrease stripe size until can no longer be resolved

5

Are vertical or horizontal pursuits more accurate?

horizontal

6

What is the development of the OKR like during infancy?

1. temporal to nasal OKR develops first so stronger monocular response
2. asymmetry disappears by 2 to 6 months
3. asymmetry remains if strabismus/amblyopia

7

What are the neurological pathways involved in the OKN?

1. accessory optic system (AOS) in midbrain
2. nucleus of optic tract (NOT) in midbrain

8

What is the gain for a patient told to stare ahead passively for a "stare OKN"? 1. Gain for when told to fixate a feature of the stimulus for a "look OKN"? 2

1. 0.80
2. 1.00

9

What is the interaction of the OKR and the VOR?

1. OKR helps take over to stabilize visual scene by providing positive after-effect to counterbalance RVOR negative after-effect
2. helps to stabilize world during post-rotational nystagmus

10

What is the latency of the OKR?

140ms (slow compare to RVOR and TVOR)

11

What are the major uses of OKN?

1. estimate VA
2. check for cortical blindness (need occipital cortex to have response)
3. screen for amblyopia and strabismus (will be better temporal to nasal)

12

What is a reflexive eye movement that requires visual input called?

psychooptical reflex

13

What drugs can eliminate smooth pursuits but leave saccades intact? 1. Can pursuits be improved with training (and what are the limitations)? 2

1. barbiturates
2. yes (plateau at same level and for baseball can only pursue ball if beyond 10 feet away when batting)

14

What is the latency of pursuits? 1. At what target velocity can pursuits closely match? 2

1. 100 plus or minus 5ms
2. 60 to 70deg/sec or less

15

What is triggered if the eyes are behind a pursuit target?

catch-up saccade

16

What factors contribute to the accuracy of a pursuit eye movement?

1. age (decline with age)
2. target prediction (educated guess of future behavior)

17

What are the 2 plots that contribute to the Bode analysis for pursuits?

1. gain vs frequency
2. phase vs frequency

18

What is a slow, conjugate tracking eye movement in response to a moving stimulus? 1. What is the primary stimulus for this? 2

1. pursuit eye movements
2. target velocity

19

What is an involuntary jerk nystagmus caused by the OKR? 1. How is this clinically elicited? 2

1. optokinetic nystagmus
2. presenting a moving square wave pattern (alternating black and white stripes)