Department of ORL-HNS Maastricht University Medical Centre The Netherlands comparison video-oculography and electro-nystagmography using the search coil technique as a golden standard azMazM

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-nystagmography 50 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 standard in 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 EOGVOG 2D /3D2D2D sometimes 3D accuracy < 3°< 0.5° precision (reproducibility) < 1°< 0.5° spatial resolution< 0.5 ° < 0.2 ° field of view H x Vunlimited40 x 40° range H x V 80 x 60°40 x (10-40)° linearity horizontal 25°25° linearity vertical20°20° drift0 – 5 °/s 0°/s artefactsEMG,ECG, blinksblinks eyes openokok eyes closedoknot possible impact of lightyes: CRP! no calibrationnecessarynot necessary applicability98%80%

EOG versus VOG are EOG and VOG appropriate to detect saccade 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 points not 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 ms validation Nyquist reconstruction algorithm with SCT 1000 Hz 50 Hz 50 Hz reconstructed small saccade large saccade

simulation using SCT 1000 Hz vs 50 Hz

ms application for VOG of Nyquist reconstruction algorithm 50 Hz 50 Hz reconstructed smalllarge 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 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 azMazM