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AE Gallagher, CS Chen, DC Hood; A Comparison of Multifocal Visual Evoked Potentials (mfVEP) Recorded With Different Electrode Positions . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2172.
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Purpose: To compare multifocal visual evoked potentials (mfVEP) recorded with three sets of electrode positions. Methods: Three mfVEPs were recorded from the right eye of 10 subjects (mean age 29+/-12 yrs) with no known visual abnormalities. For one set of positions (Hetal ), the electrodes were held in place with wrap while the other two configurations (G&K and G&Kinv) used an electrode holder (ObjectiVision, Sydney, Australia) . The three configurations were: Hetal (inion (I), 4 cm above I, and 1 cm up and 4 cm to the right and left of I), G&K (4.5 cm below I, 3 cm above I, and 4 cm to the right and left of I), and the G&Kinv (G&K electrode holder inverted, i.e. 4.5 cm above I and 3 cm below I). Pattern-reversed mfVEPs were recorded using a 60-sector stimulus array (Dart Board 60 With Pattern, EDI). The records were amplified with cutoffs at 3 and 100 Hz and filtered offline with a FFT lowpass filter (35 Hz). Within each session, two 7-minute recordings were obtained. The three channels of recordings were obtained simultaneously with three additional channels derived. A signal-to-noise ratio (SNR) was determined for each of the 60 monocular responses by dividing the root mean square (RMS) of a signal window (45 to 150 ms) by the mean RMS of the 60-noise windows (325 to 430 ms) for each subject. For each subject, the best channel was also calculated for each of the 60 locations by choosing the channel with the largest SNR. Results: For the midline channel, the mean SNRs were 2.4 (G&Kinv), 2.3 (Hetal), and 1.5 (G&K). The largest SNR was obtained with the Hetal configuration for 6/10 of the subjects. For the best channel, the mean SNRs were 3.6 (Hetal), 3.0 (G&Kinv), and 1.8 (G&K). The largest SNR was obtained with the Hetal configuration for 7/10 subjects. Using the midline channel, analysis of the mean SNR values of the upper hemifield show that the G&Kinv configuration produced the largest mean SNR (2.3), while the mean SNRs for Hetal and G&K were 2.2 and 1.5, respectively. Conclusions: From anatomical considerations, we know that one electrode configuration will not be ideal for everyone . However, either the Hetal or the G&Kinv configuration appears preferable to the G&K configuration. 1. Hood et al (in press) Doc. Ophth 2. Klistorner & Graham, Ophthal, 2000 3. Hood & Zhang (2000) Doc. Ophth.
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