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Effect of stimulus check size on multifocal visual evoked potentials
Chandra Balachandran1, Alexander I Klistorner, Stuart L Graham
1Save Sight Institute, Department of Ophthalmology, University of Sydney, Sydney, Australia.
Documenta Ophthalmologica. Advances in Ophthalmology
|April 8, 2003
Summary
The study found that 16 checks per segment is optimal for multifocal visual evoked potential (VEP) testing. Adjusting check size impacts VEP latency, particularly in the central visual field.
Area of Science:
- Ophthalmology
- Neuroscience
- Visual electrophysiology
Background:
- Multifocal visual evoked potential (VEP) is crucial for assessing visual field function.
- Current methods use cortical scaling of stimulus segments, but optimal check size requires investigation.
Purpose of the Study:
- To determine the effect of varying stimulus check sizes on multifocal VEP.
- To evaluate the efficacy of current cortical scaling in stimulus segment presentation.
Main Methods:
- Tested stimuli with 9, 16, 25, 36, and 49 checks/segment on 10 normal subjects.
- Recorded VEP using bipolar occipital electrodes.
- Analyzed VEP amplitude and latency in relation to check size and eccentricity.
Main Results:
- The setting with 16 checks/segment (26' to 140' from center to periphery) demonstrated the most effective VEP response.
- Reducing check size primarily increased latency in the central visual field.
- Cortical scaling provided consistent response magnitudes but could be refined for peripheral signals.
Conclusions:
- The standard 16 checks/segment setting is optimal for multifocal VEP.
- Stimulus check size significantly influences VEP latency, especially centrally.
- Cortical scaling is effective but has room for improvement in peripheral signal detection.