Saccadic intrusions!
Louis Émile Javal (1839 – 1907)
“during reading… eyes do not move continuously along a line of text, but make short rapid movements (saccades) intermingled with short stops (fixations)”
2) Normal vs abnormal
Normal saccades - help fixation
Saccadic intrusions - interrupt fixation
*In the absence of quantitative eye movement recordings, simply counting gaze fixation breaks (>9/min) may suffice
3) Types of saccadic intrusions
Square wave jerks (SWJ)
Macrosquare wave jerk
Macrosaccadic oscillations
Saccadic pulses
Ocular flutter
Opsoclonus
Voluntary nystagmus or flutter
*defined by eye position, amplitude (size), and velocity
4) Saccadic intrusions ≠ nystagmus ≠ saccadic dysmetria
Saccadic intrusions
-omnipause neuron def
-pause cell dysfunction (fast-fast)
Nystagmus
-neural integrator def
-leaky integrator (fast-slow)
Saccadic dysmetria
-cerebellum def
-eye over/undershoot before landing on target
5) Square wave jerks (SWJ) aka Gegenrucke
- 0.5 to 5 degrees
- intersaccardic interval (200 msc)
5.1. SWJ
-most common saccadic intrusion
- intersaccadic interval
- fixate on the camera, sir! But saccades interrupt fixation
5.2. SWJ
≠ nystagmus: no slow phase
- healthy individuals, usually elderly
5.4. SWJ
- long intersaccardic interval
- intersaccadic interval
6) Macrosquare wave jerk
- > 5 degrees
- 2-3 Hz
- intersaccardic interval (200 msc)
- burst occurrence (vary amplitude)
- monocular vision suppression
6.1. MSWJ
7) Macrosaccadic oscillations
- inc-dec amplitude
- intersaccardic interval (200 msc)
- burst occurrence
7.1. MSO
- intersaccadic interval
- variable amplitude
8) Saccadic pulses
- small-amplitude saccades away from fixation followed by a rapid drift back
- “flutter in pulses”
9) Flutter
- horizontal saccades
*microflutter can have vertical & torsional
- no intersaccadic interval
9.1. Ocular Flutter
- fixation, fast-fast component
- horizontal
- no intersaccadic interval (back-to-back horizontal oscillatory movements)
9.2. Ocular flutter
- burst horizontal fast-fast moves with no intersaccadic interval
- "pause" neurons usually prevent saccadic oscillations during fixation by inhibiting "bursts" neuron firing
> saccadic intrusion - pause neuron lesion
9.3. Ocular flutter
- short eye movements (avoiding fixation) to prevent flutter initiation
9.4. Ocular flutter
- horizontal fast-fast
- occur at primary gaze
- can not be elicited by eye movement
9.5. Benign ocular flutter
- challenging to assess fixation
> color and bright stationary object
- subjectively assess oscillopsia
> feeding
10) Opsoclonus
- multidirectional, horizontal, vertical, and torsional saccadic oscillations
- no intersaccadic interval
10.1. Opsoclonus in the oscilloscope screen
"die in the eye and record eye movements"
- multidirectional
- varied amplitude
- no intersaccadic interval
- all directions fast-fast component
- worsen w/ convergence
10.3. Opsoclonus- 1st patient with opsoclonus due to anti-Ri in setting of breast cancer
10.4. Opsoclonus
- multidirectional
- fast-fast component
- no intersaccadic interval
10.5. Opsoclonus
- ramdon caotic saccades
- occurring at fixation
10.6. Opsoclonus
- multidirectional
- fast-fast component
- no intersaccadic interval
10.7. Opsoclonus
-multidirectional
10.8. Opsoclonus
- multidirectional
- no intersaccadic interval
11) Voluntary flutter/nystagmus
“ability to induce nystag & flutter”
- high frequency (usually, > 15 Hz)
- duration < 30 sec
- precipitated by convergence
- superimposed by smooth-tracking
*psychogenic: convergence effort, facial grimacing, eyelid flutter
11.1. Voluntary Ocular Flutter
≠ from ocular flutter:
- convergence elicits flutter
- unsustained
- near triad cause miosis
11.2 Voluntary ocular flutter
- stop w/ closing eyes
- eyelid flutter
- forcing convergence to occur flutter
> patient did not notice that she was purposefully converging for this to occur