Advantages of EOG
- The EOG is linearly proportional to eye displacement.
- The EOG is easy to use (in children and patients confined to bed).
- The signals are measured with respect to the head.
- Registration of eye movements with closed eyelids and during sleep are possible.
- Artifacts from eyelid blinking can be detected easily.
- Eye movement data is analog and the sampling rate of a following analog-digital-converter (ADC) can be chosen freely.
- The EOG is the most inexpensive eye movement recording system.
- This can be used with glasses or contact lenses, unlike some reflection methods.
- The necessary fixtures do not obstruct the visual field.
- With naso-temporal electrode application the linearity amounts to ± 20 degrees, with bi-temporal up to ± 30 degrees
Disadvantages of EOG
- This signal seldom is deterministic, even for same person in different environment.
- The EOG signal is a result of a number of factors, including eyeball rotation and movement, eyelid movement, different sources of artifact such as EEG, electrodes placement, head movements, influence of the luminance.
- EOG signal increase if the luminance increase.
- These EOG systems have a disadvantage that the detected signals are easily contaminated with drift in long-term measurements.
- However, the EOG suffers from a lack of accuracy at the extremes, due to noise compounded from the effects of an EEG, EMG, and the recording equipment equivalent to approximately 100 of eye movement. Thus movements of less than 100 are difficult to record.
- In addition, large eye movements do not produce bioelectric amplitudes that are proportional to eye position.
- Variation in skin resistance, electrode slippage or polarization, even a variable corneoretinal potential due to light accommodation and level awareness.
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