Optokinetic Response and Pursuits (M2)

Question 1

What type of eye movement is the optokinetic response?

Answer 1

gaze holding eye movement

Question 2

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

Answer 2

1. little to no effect

2. malingering, infants, IDD patients

Question 3

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

Answer 3

right

Question 4

How can OKN be used to estimate VA?

Answer 4

decrease stripe size until can no longer be resolved

Question 5

Are vertical or horizontal pursuits more accurate?

Answer 5

horizontal

Question 6

What is the development of the OKR like during infancy?

Answer 6

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

Question 7

What are the neurological pathways involved in the OKN?

Answer 7

1. accessory optic system (AOS) in midbrain

2. nucleus of optic tract (NOT) in midbrain

Question 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

Answer 8

1. 0.80

2. 1.00

Question 9

What is the interaction of the OKR and the VOR?

Answer 9

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

Question 10

What is the latency of the OKR?

Answer 10

140ms (slow compare to RVOR and TVOR)

Question 11

What are the major uses of OKN?

Answer 11

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)

Question 12

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

Answer 12

psychooptical reflex

Question 13

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

Answer 13

1. barbiturates

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

Question 14

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

Answer 14

1. 100 plus or minus 5ms

2. 60 to 70deg/sec or less

Question 15

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

Answer 15

catch-up saccade

Question 16

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

Answer 16

1. age (decline with age)

2. target prediction (educated guess of future behavior)

Question 17

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

Answer 17

1. gain vs frequency

2. phase vs frequency

Question 18

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

Answer 18

1. pursuit eye movements

2. target velocity

Question 19

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

Answer 19

1. optokinetic nystagmus

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