Purchase this article with an account.
B.D. Gomes, G.S. Souza, A.R. Rodrigues, C.A. Saito, L.C. L. Silveira, M. daSilvaFilho; Color Discrimination Ellipses in Normal Trichromatic Color Vision Subjects and in a Dichromatic Subject Using Transient VECP . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5374.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To measure human color discrimination ellipses using transient Visual Evoked Cortical Potential (tVECP). Comparison of results obtained with electrophysiology and psychophysics.
C.I.E 1976 chromaticity diagram was used throughrout as a coordinate reference system. Six normal trichromats (24±1 years–old) and one deutan (26 years–old) were tested. Horizontal isoluminant sinewave gratings were made from color pairs located along 4 different color directions radiating from two reference points (u’=0.219, v’=0.48; u’=0.225, v’=0.415), 2 cycles per degree (cpd), onset (300 ms) / offset (700 ms) presentation mode. Each subject performed a heterochromatic flicker photometry (HFP) assessment to determine his/her isoluminance condition for all color axes. Monocular N1 tVECP amplitudes were plotted against color distances to find color thresholds by extrapolation to the null amplitude value. Psychophysics thresholds were obtained by using the same stimulus with an onset/offset and a static presentation mode. Furthermore, thresholds were estimated by our homemade Mollon–Reffin Test (Rodrigues et al., 2006). In each method, we found the best elliptical function to fit the data.
We found a negative deflection in the tVECP related to chromatic difference. As the difference decreased, amplitude also decreased, and latency increased. tVECP thresholds were similar to those obtained with psychophysics using sinusoidal stimuli for all subjects, however smaller than those obtained using Mollon–Reffin Test. Normal color vision subjects had vertically oriented ellipses with small size and low ellipticity. For the deutan subject, ellipses had larger size, higher ellipticity, and were oriented towards the deutan copunctal point.
The present work extends the use of tVECPs as a tool to evaluate human color vision. The tVECP results were consistent with psychophysics methods using the same stimulus configuration.
This PDF is available to Subscribers Only