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T. Meigen, M. Kraemer; Binocular Summation of Multifocal Visual Evoked Potentials Does Not Depend on Eccentricity. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2341.
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© ARVO (1962-2015); The Authors (2016-present)
The multifocal visual evoked potential (mfVEP) is an important diagnostic tool to study visual pathway function. The aim of this study was to test whether the binocular summation of mfVEP responses depends on the eccentricity of the stimulus location within the visual field.
29 subjects with normal acuity and normal stereo vision (as quantified by the TNO test) participated in the experiment. Their age ranged from 24 to 55 years. Dartboard patterns with 60 fields were presented within a circular stimulus field with a diameter of 38°. Within the dartboard fields checkerboard patterns with a mean luminance of 86,1 cd/m2 and a contrast of 99.8% were reversed in contrast following m-sequence stimulation. Binocular mfVEPs and two monocular mfVEPs for the left and right eye were recorded from an electrode arrangement with two electrodes 4 cm above and below the inion. Root-mean-square (RMS) amplitudes were derived in three steps. First we summed the squared second order mfVEP traces across (a) all 60 fields, and (b) 5 concentric rings of the 60 stimulus fields. Second, we calculated the mean for each of these sums of squares in the time interval between 50 and 170 ms. Third, the time interval between 360 and 480 ms was used to estimate the noise level and to remove noise contributions from the RMS amplitude. Finally, we quantified the binocular summation by the ratio of the RMS amplitude for the binocular mfVEP to the RMS amplitude for the mean of both monocular recordings for each subject and for each subset of the 60 stimulus fields.
The ratio of binocular summation was 1.40 ± 0.03 (mean ± SEM) when analyzing RMS amplitudes across all 60 stimulus fields. The mean ratios of binocular summation for the 5 rings were 1.46 ± 0.05 (central ring), 1.38 ± 0.03 (ring 2), 1.39 ± 0.04 (ring 3), 1.42 ± 0.05 (ring 4), and 1.43 ± 0.05 (ring 5). (c) The ANOVA showed that the eccentricity of the stimulus fields had no significant effect on the ratio of binocular summation (p > 0.53).
Our data suggest that binocular summation of mfVEP signals does not depend on eccentricity. The uniform ratio of binocular summation across the visual field may facilitate future applications of mfVEPs to study binocular visual function in basic research and in the clinical routine.
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