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Monique Smyth, Caroline Kilemi, Givago Souza, Carolina Araujo, Eliza Maria Lacerda, Mellina Jacob, Bruno Gomes, Malinda Fitzgerald, Luiz Carlos Silveira; Chromatic and achromatic contribution to the multifocal visual evoked potentials. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6142. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the contribution of chromatic and achromatic mechanisms to multifocal visual evoked potentials generation.
The multifocal visual evoked potential of twelve trichromat subjects was recorded for seven red-green luminance combinations and one black-white condition. The stimuli were 60 checkboard sectors dartboard controlled by an m-sequence simulating pattern reversal presentation mode. Red-green luminance ratios varied from 0.2 to 0.8 in 0.1 steps, and the black-white condition was at 99% of Michelson contrast. First-slice of second order kernel were extracted and analyzed. The rate of reliable mfVEP waveforms was quantified and the mean RMS amplitude of these waveforms was calculated in six set of sectors of same eccentricities, from R1 to R6, where R1 was in the center of the visual field and R6 is the outer area in the visual field.
The mean rate of reliable waveforms versus red-green luminance ratio function had a V-shape across the visual field. The minimum rate of reliable mfVEP waveforms was found at luminance ratio 0.5 (low luminance contrast, high chromatic contrast) and the maximum rate of reliable mfVEP waveforms was found at 0.2 or 0.8 (high luminance contrast, low chromatic contrast) luminance ratios. At achromatic condition and red-green luminance ratios of 0.2, 0.3, 0.7, and 0.8 the sectors with highest mfVEP waveform reliability rate were in R3 and R4. At the red-green luminance-ratios 0.4, 0.5, and 0.6 the highest mfVEP waveform reliability rate occurred at, mainly, R2 and R3. The ratio of the reliability rate between the chromatic ratio 0.5 and achromatic was higher at R1 and lower at R6. Mean mfVEP amplitude versus red-green luminance ratio function had a U-inverted shape at R1 and R2, with maximum amplitude at color ratios between 0.4 and 0.6. At R3-R6 the mfVEP amplitude had few changes across the color ratio domain. The central rings elicited highest mfVEP amplitude at all color ratios, but for achromatic condition, the highest amplitude was found at R2-R4. The ratio between the mfVEP amplitude at color ratio 0.5 and achromatic condition was higher at R1 and decreased until a similar level at R4-R6.
The combination of luminance and chromatic stimulation increased the reliability rate of the sectors, but did not increase the mean mfVEP amplitude. Chromatic contribution to the mfVEP decreased from the center to the periphery of the visual field.
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