department of orl-hns maastricht university medical centre the netherlands
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a z M. comparison video-oculography and electro-nystagmography using the search coil technique as a golden standard. Department of ORL-HNS Maastricht University Medical Centre The Netherlands. EOG versus VOG which eye movement recording technique - PowerPoint PPT PresentationTRANSCRIPT
Department of ORL-HNSMaastricht University Medical Centre
The Netherlands
comparison video-oculography and electro-nystagmography using the search coil technique as a golden standard
azM
EOG versus VOG
which eye movement recording technique is optimal for the clinical setting ?
- clinical relevant eye movement types: spontaneous, fixation, pursuit, saccades, nystagmus
- requirements: easy and comfortable application accuracy, precision, spatial resolution (Δ°), time resolution (Δt)
electro-oculography /electro-nystagmography50 Hz, drift, eye-blink + EMG artifacts, 2D, EO+EC
video-oculography (VOG) / video-nystagmography (VNG)50 Hz, 3D but limited range, only EO
search coil technique (SCT): golden standardin clinic not accepted, 1000 Hz, 3D, EO + EC
EOG versus VOG
which eye movement recording technique is optimal for the clinical setting ?
- clinical relevant eye movement types:spontaneous, fixation, pursuit, saccades, nystagmus
- requirements: easy and comfortable application accuracy, precision, spatial resolution (Δ°), time resolution (Δt)
EOG versus VOG
which eye movement recording technique is optimal for the clinical setting ?
method:
- simultaneous recording of eye movements with EOG, VOG and SCT- exclusion of interference between the techniques- 6 healthy subjects- comparison of accuracy / drift / artefacts- comparison of time resolution
accuracy horizontal
EOG VOG
accuracy vertical
EOG VOG
- vertical eye movements can be analysed with EOG !- limited range EOG and VOG: 20°
detection of eye position
EOG VOG2D /3D 2D 2D sometimes 3Daccuracy < 3° < 0.5°precision (reproducibility) < 1° < 0.5°spatial resolution < 0.5 ° < 0.2 °field of view H x V unlimited 40 x 40°range H x V 80 x 60° 40 x (10-40)°linearity horizontal 25° 25°linearity vertical 20° 20°drift 0 – 5 °/s 0°/sartefacts EMG,ECG, blinks blinkseyes open ok okeyes closed ok not possibleimpact of light yes: CRP! nocalibration necessary not necessaryapplicability 98% 80%
EOG versus VOG
are EOG and VOG appropriate to detectsaccade latencies and peak velocities (time resolution) ?
method: - simultaneous recording of eye movements with EOG, VOG and SCT- exclusion of interference between the techniques- 6 healthy subjects- comparison of accuracy / drift / artefacts- comparison of time resolution:
* analysis of frequency compound of eye movements (SCT) in relation to the limited frequency range of EOG (noise) and VOG (25-50 Hz sample frequency)
* development of special signal analysis techniques for VOG
frequency content saccades
sct eog
eog: high frequency noise bandwidth can be limited from 0 to about 25 Hz
sample frequency of 50 Hz sufficient
noise
0 50 ms
VOG
which eye movement recording technique is optimal for the clinical setting ?
are EOG and is VOG appropriate to detect saccade peak velocities
- problem with VOG: 50 Hz ~ 20 ms saccade lasts only 50 ms: 2 data pointsnot enough to reconstruct peak velocity ?literature: you need minimum 300 Hz
Nyquist signal reconstruction technique used
to calculate eye velocities (IEEE, 2007 )
simulation using SCT 1000 Hz vs 50 Hz
0 50 100 150 200 0 100 200 300 400 ms
0 50 100 150 200 0 100 200 300 400 ms
validation Nyquist reconstruction algorithm with SCT
1000 Hz 50 Hz 50 Hz reconstructed
smallsaccade
largesaccade
simulation using SCT 1000 Hz vs 50 Hz
simulation using SCT 1000 Hz vs 50 Hz
0 200 400 600 800 0 100 200 300 400 500 ms
application for VOG of Nyquist reconstruction algorithm
50 Hz 50 Hz reconstructed
small large
0 200 400 600 800 0 100 200 300 400 500 ms
simulation using SCT 1000 Hz vs 50 Hz
application for VOG of Nyquist reconstruction algorithm
NB: peak velocities VOG even higher than peak velocities SCT ! artifact ?
- asymmetry EOG in case of monocular detection: artifact - binocular detection (100 Hz LPF, 1000 Hz SF): good estimates of latencies and peak velocities
NB: peak velocities EOG even higher than peak velocities SCT ! artifact?
leftwards rightwards
OD
ODOS
OS
ODS
is EOG appropriate to detect saccade peak velocities and latencies ?
comparison data SCT+VOG+EOG versus VOG+EOG:
- eye velocities detected with EOG and VOG are slower with COIL on the eye than without COIL on the eye
- search coil slows down eye velocities
peak velocities of both EOG and VOG are higher than peak velocities SCT !
visual check of VOG images of the eye with search coil:
search coil slips over the eye
- SCT- no perfect golden standard (coil slips and slows down the eye)
- VOG - optimal for BPPV - OD and OS saccades can be analysed with a 50 Hz system- but field of view and range are limited
- often detection fails (> 20% !) and 3D is often unreliable- EOG
- robust clinical method for binocular recordings- eo / ec, unlimited field of view, large range of detection H+V - only binocular saccades can be analysed reliable- but drift and noise can hamper a good detection (training)
EOG versus VOG which technique
is optimal for the clinical setting ?
• EOG is the first choice to deal with all patients
• VOG is very useful for BPPV and complex patients
azM