EOG Signal Processing Guide
Electrooculography (EOG) measures voltage changes caused by the standing electrical potential between the cornea and retina. As the eyes move, the measured signal changes, making EOG useful for reviewing blinks, saccades, gaze shifts and eye-movement artifacts in EEG recordings.
A professional EOG workflow should make slow eye movements visible while reducing baseline drift, powerline interference and high-frequency noise that can make blink and saccade boundaries harder to inspect.
What EOG Measures
EOG electrodes are usually placed around the eyes. Vertical EOG channels capture blinks and up-down movements, while horizontal EOG channels capture left-right movements and saccades. Because EOG amplitudes are often larger than EEG, eye activity can also appear as a strong artifact in frontal EEG channels.
Common EOG Events
Blinks
Blinks are usually large, brief deflections in vertical EOG. They can be useful events in sleep, attention and fatigue studies, but they can also contaminate nearby EEG channels.
Saccades
Saccades are rapid eye movements between fixation points. In horizontal EOG, they often appear as sharp transitions followed by a new signal level.
Slow Eye Movements
Slow rolling eye movements are lower-frequency patterns often reviewed in sleep staging and drowsiness research. These signals require careful drift handling so the physiological trend is not removed accidentally.
Recommended EOG Filter Settings
EOG is a low-frequency biosignal, so filtering should be gentler than EMG and often closer to slow EEG preprocessing. The exact settings depend on whether you are reviewing blinks, saccades, slow eye movements or EEG artifact channels.
Standard EOG filter preset
- High-pass filter: 0.05 Hz to 0.1 Hz, order 2 or 4.
Reduces slow baseline drift while preserving meaningful eye-movement trends. - Notch filter: 50 Hz or 60 Hz.
Targets powerline interference when it appears in the recording. - Low-pass filter: 30 Hz to 40 Hz, order 4.
Preserves blink and saccade morphology while reducing high-frequency noise.
How to Analyze EOG Data Online
BioSignal Workstation gives you a fast way to review EOG recordings without installing a full signal-processing environment.
- Upload your EOG file: open CSV, TXT, XLS or XLSX data in the BioSignal Workstation analyzer.
- Select EOG channels: choose vertical and horizontal channels if your recording includes both.
- Apply gentle filtering: start with a low high-pass cutoff for drift and a low-pass cutoff around 30 Hz to 40 Hz.
- Inspect eye events: review blinks, saccades and slow eye movements in the time-domain chart.
- Export clean data: save filtered channels or ROI measurements for reports and downstream analysis.
Validate EOG with PSD and Time-Domain Review
EOG interpretation is usually time-domain first because blinks and saccades have recognizable shapes. PSD is still useful for checking whether drift, powerline noise or high-frequency contamination is dominating the signal. After filtering, the EOG trace should preserve eye-event morphology while showing reduced mains spikes and less unstable baseline motion.
EOG Analyzer FAQ
Can I analyze EOG CSV files online?
Yes. The EOG analyzer page is designed for browser-based review of EOG data from CSV, TXT, XLS and XLSX files.
What filter settings should I start with for EOG?
Start with a 0.05 Hz to 0.1 Hz high-pass filter, a 50 Hz or 60 Hz notch filter if needed, and a 30 Hz to 40 Hz low-pass filter for blink and saccade review.
Can EOG help identify eye artifacts in EEG?
Yes. EOG channels are commonly used to mark blinks and eye movements that may contaminate frontal EEG channels, making them useful for artifact review and documentation.