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Visual Science: Ocular Motility > Ocular Motility: Lecture 5: Fixational Eye Movements > Flashcards

Ocular Motility: Lecture 5: Fixational Eye Movements Flashcards

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1
Q
  1. Does the eye remain perfectly motionless during an attempted steady fixation on a Stationary Object?
A
  1. NO! it does not
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2
Q

Fixational Area Increases w/Increased Fixation Duration

  1. Fixation for 10 seconds?
  2. 20 seconds?
  3. for 1 minute?
A
  1. +/- 7.5 min arc
  2. +/- 30 min arc
  3. Fixation is CENTRAL and in CLOSE Proximity to the target
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3
Q

Eye movements During Fixation

What 3 things occur?

A
  1. Drift
  2. Microsaccade
  3. Tremor
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4
Q

Eye Movements

  1. Tremor: What is it?
    a. Relation to AMPLITUDE?
    b. What is it in the Oculomotor System?
    c. Impact on Vision?
  2. Freq?
  3. Amp?
  4. Vel?
  5. OU?
  6. Other?
A
  1. High Frequency movement ranging from 30-100 Hz
    a. Inversely Related to Amplitude
    b. Noise
    c. No
  2. 30-100 Hz
  3. 20 arc secs
  4. 30 arc min/sec
  5. Not correlated
  6. Frequency inversely related to Amplitude
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5
Q

Eye Movements

  1. Drift: What is it?
  2. Drift Amplitude INCREASES slightly when what is generated?
  3. Drift makes up more than 95% of what?
  4. Freq?
  5. Amp?
  6. Vel?
  7. OU?
  8. Other?
A
  1. A Low Velocity Irregular Eye Movement
  2. When Retinal Errors are generated from the Near and Far Retinal Periphery
  3. of one’s Total Fixation Time

4.

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6
Q

Eye Movements

  1. Microsaccade: What is it?
  2. Freq?
  3. Amp?
  4. Duration?
  5. OU?
  6. Other?
A
  1. Error Correcting
  2. 1-2/sec
  3. 1-25 min arc; Mean is 5 min arc
  4. 10-25 msec
  5. Bin & High Amp correlation
  6. Large Dynamic Overshoot
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7
Q

Ocular Drift

  1. Light: What happens to Ocular Drift?
  2. Dark: What happens to Drift Velocity?
  3. What are drifts?
  4. In the presence of Visual feedback, what happens to the Accuracy of Fixation?
A
  1. It INCREASES over a 1.6 sec period
  2. Drift Velocity is INCREASED
  3. Error producing and Microsaccades are Error Correcting
  4. It was GREATLY INCREASED
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8
Q
  1. Fixational Eye Movement is ROBUST to changes in response to what?
  2. Fixation in Darkness has the MOST what?
  3. Is there an Age related Effect in Overall Stability?
A
  1. to EXTERNAL STIMULI
  2. the Most Deleterious Effects on Accuracy of Fixation
  3. NO!
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9
Q

Neurophysiology of Fixation

  1. What 6 areas are involved?
A
  1. Parietal Eye Field (Lateral Interparietal Area and Area 7a in monkeys)
  2. V5 and V5A (MT and MST in Monkeys)
  3. Supplementary Eye Field
  4. Dorsolateral Prefrontal Cortex
  5. Substantia Nigra Pars Reticulata in the Basal Ganglia
  6. Rostral Pole of the Superior Colliculus
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10
Q

Anormal Fixation

  1. What 3 things are there?
A
  1. Nystagmus
  2. Saccadic Intrusion
  3. Slow Drift
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11
Q

Aberrant Tremor

  1. What is it?
  2. ABSENCE of what?
  3. PRESENCE of what 2 things?
  4. Extended periods of what?
  5. OVERALL REDUCTION in what?
A
  1. Different Overall Patterns b/w the 2 eyes.
  2. of High-Frequency Bursts
  3. of Irregular and Low Frequency Bursts of Latitude
  4. of Very Low-Frequency Movement
  5. in the Dominant Frequency Response
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12
Q

Slow Drift

  1. Found in Persons with what?
  2. Amplitude of up to what?
  3. Velocity less than what?
  4. Frequency?
  5. Generally not rapid enough to degrade what?
  6. Observed with what?
  7. Drift Improves with what?
A
  1. with Functional Amblyopia
  2. 1 degree
  3. than 3 degrees per second
  4. Irregular, Slow Frequency (
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13
Q

Saccadic Intrusions

  1. Found in what 3 things?
  2. What does it do?
  3. Is it affected by age?
A
  1. Normals, Functional Strabismus, and Cerebellar Disease
  2. Jerks the eye away from the object of regard via a SACCADE and Approx 200 msec later return the eye back to original position by a second opposite second (??)
  3. No
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14
Q

Square Wave Jerk

  1. What can they be found in?
  2. Amplitude
  3. Time Course
  4. Latency
  5. Foveation
  6. Presence in Darkness
A
  1. Sq-wave jerks found in Strabismus can be transiently suppressed
  2. 0.5-3 deg, constant
  3. Sporadic
  4. 200 msec
  5. Yes
  6. Yes
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15
Q

Saccadic Intrusions (2)

  1. Macro Square-wave Jerks are what?
    a. They occur more frequently (how much)
    b. They remove the eye from the target for how much time?
    c. Found in what 2 things?
  2. Amplitude
  3. Time Course
  4. Latency
  5. Foveation
  6. Presence in Darkness
A
  1. Are LARGER
    a. 2-3 Hz
    b. For a Shorter Period of time (100 msec)
    c. Cerebellar Disease and MS
  2. 4-30 degrees
  3. Bursts
  4. 50-150 msec
  5. Yes
  6. Yes
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16
Q

Saccadic Intrusions (3)

  1. Macrosaccadic Oscillations
    a. Sequence of saccades doing what?
    b. Intersaccadic Pauses or Intervals of how much time?
    c. Found in what disease?
  2. Amplitude
  3. Time Course
  4. Latency
  5. Foveation
  6. Presence in Dakness
A
  1. a. INCREASING then DECREASING Amplitude to EITHER SIDE Of the FIXATION POINT
    b. 200 msec
    c. Cerebellar Disease
  2. 1-30 degrees
  3. Bursts
  4. 200 msec
  5. No
  6. No
17
Q

Nystagmus

  1. What is it?
  2. % of patients w/Strabismus have Nystagmus?
  3. % of patients w/Congenital Nystagmus that have Strabismus?
  4. Head turn in a direction opposite to what?
A
  1. Rhythmic Oscillation of the Eye
  2. 50%
  3. 15%
  4. to their null position
18
Q

Nystagmus (2)

  1. Early Onset Nystagmus
    a. AKA?
    b. What 2 are there?
A
  1. a. Congenital Nystagmus or Infantile Nystagmus Syndrome

b. Sensory Defect Nystagmus (Including Albinism) and Motor Defect Nystagmus (Congenital Idiopathic Nystagmus)

19
Q

Nystagmus (3)

  1. Latent Nystagmus
    a. AKA?
    b. What 2 types?
A
  1. a. Fusion Maldevelopment Nystagmus Syndrome

b. Latent Latent Nystagmus, and Manifest Latent Nystagmus

20
Q

Nystagmus (4)

  1. Acquired
    a. AKA?
    b. 6 of them
A
  1. a. Neurological Nystagmus
    b. Acquired Pendular

Acquired Jerk

Convergence Retraction

Gaze Paretic (Evoked)

See-Saw

and

Vestibular Nystagmus

21
Q

Characteristics and Observations

  1. General Observations
  2. Apparent Type of Nystagmus
  3. Direciton
  4. Amplitude
  5. Frequency
  6. Constancy
  7. Conjugacy
  8. Latent Component
  9. Position of Gaze Changes
A
  1. General Posture, Facial Asymmetries, Head Posture
  2. Pendular, Jerk or mixed
  3. Horizontal, vertical, torsional or a combo
  4. Small ( movements approximately parallel), Disjunctive (Eyes move independently) or monocular
  5. Does nystagmus increase or change w/occlusion of 1 eye. If so, does it always beat away from the covered eye (pathognomonic of latent nystagmus)
  6. Null point; does nystagmus increase or decrease in any field of gaze or with convergence
22
Q

Pendular Nystagmus

  1. Velocity of Movement
  2. Foveation
  3. Null Position
A
  1. Similar in both directions
  2. Occurs when the eye velocity is the lowest
  3. Present
23
Q

Jerk Nystagmus

  1. Velocity of Movement
  2. Foveation
  3. Null Position
A
  1. Slow in one direction and Rapid Saccade in opposite
  2. Occur immediately after the rapid saccade
  3. present
24
Q

Pendular Nystagmus

  1. High-gain instability in what?
  2. What -scopy?
  3. Amplitude
  4. Frequency
  5. Peak Velocity
A
  1. in the Slow-Control System
  2. Visuoscopy
  3. 0.5-10 degrees
  4. 2-8 Hz
  5. up to 100 degrees/sec
25
Q

Pendular Nystagmus: Congenital Pendular

  1. Direction
  2. Variability
  3. Systemic Disorder
A
  1. Horizontal
  2. Less variable b/w the 2 eyes
  3. Associated w/Albinism
26
Q

Pendular Nystagmus: Acquired

  1. Direction
  2. Variability
  3. Systemic Disorder
A
  1. Vertical and Torsional
  2. More variable b/w the 2 eyes
  3. Associated with Myelin Disease
27
Q

Congenital Jerk Nystagmus

  1. Monocular or Binocular?
  2. Amplitude in both eyes?
  3. Diminished by what?
  4. Increased by what?
  5. VA may be what @Foveation?
  6. Amplitude
  7. Frequency?
  8. Velocity?
A
  1. Binocular
  2. Similar in both eyes
  3. by Convergence
  4. by Fixation attempt

5.

28
Q

Gazed Evoked Nystagmus

  1. Features are similar to what?
  2. Slow phase moves the eye towards what?
  3. A Saccade does what?
  4. Found in patients with what? (4)
A
  1. to Congenital Nystagmus w/the slow-phase velocity waveform of decreasing (rather than increasing) exponential variety
  2. Towards the Midline
  3. Corrects the position Error
  4. Using Certain Drugs, Cerebellar and Vestibular Problems, and MS
29
Q

Latent Nystagmus

  1. Latent: What is it?
    a. Slow phase toward what?
    b. Fast phase towards what?
  2. Manifest Latent Nystagmus: What is it?
    a. Occurs with what 2 things?
    b. Difficult to Observe with what?
A
  1. Form of Jerk Nystagmus that occurs only under monocular condition

a. Toward the occluded eye
b. in the other direction

  1. Binocular and Conjugate
    a. Strabismus and head Turn
    b. with Visuoscopy under binocular conditions
30
Q

Peripheral Vestibular Nystagmus

  1. Direction of Nystagmus
  2. Purely Horizontal Nystagmus
  3. Vertical Nystagmus
  4. Visual Fixation
  5. Severity of Vertigo
  6. Direction of Environmental Spin
    * What is Vestibular Nystagmus?
A
  1. Unidirectional
  2. Uncommon
  3. Never present
  4. Inhibits Nystagmus and Vertigo
  5. Marked
  6. Toward Slow Phase
    * Eye moves away from the object of regard and is followed by a foveating Saccade
31
Q

End Organ Vestibular Nystagmus

  1. Direction of Nystagmus
  2. Purely Horizontal Nystagmus
  3. Vertical Nystagmus
  4. Visual Fixation
  5. Severity of Vertigo
  6. Direction of Environmental Spin
A
  1. Bidirectional or Unidirectional
  2. Common
  3. May be Present
  4. No Inhibition
  5. Mild
  6. Variable
32
Q

Treatment of Nystagmus (3)

A
  1. Base Out Prism
  2. Yoked Prisms
  3. Orthoptics, Contact Lenses & Biofeedback

Visual Science: Ocular Motility (14 decks)

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