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V. J. Volbrecht, L. S. Baker, J. L. Nerger; Color Discrimination of Peripheral Stimuli and the Influence of Rods. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3471.
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The purpose of this study was: 1) to reveal the influence of rods on color discrimination in the peripheral retina, 2) to determine if the effect of rods is the same across the wavelength spectrum, and 3) to assess whether the rod effect is time dependent with rod photopigment regeneration.
Wavelength discrimination functions were derived from color-naming data obtained in the fovea and at 10° in the temporal retina using the Uniform Appearance Diagram (UAD) and methods of Abramov, Gordon, & Chan (1990). Color-naming data were obtained from 4 observers every 4 minutes for 28 minutes following a bleaching stimulus calculated to bleach >98% of photopigment when viewed for 10 sec. The 20 td stimuli ranged in wavelength from 480-620 in 20 nm steps and were presented for 500 msec on a dark background. UADs were then calculated for each data set and used to derive mean wavelength discrimination functions across the four observers at each of the separate time periods.
The UAD derivations and resulting discrimination functions were validated by comparison to previous psychophysical measurements in the literature. Peripheral wavelength discrimination functions derived 4 and 8 minutes post bleach were unchanged as compared to the fovea. As time progressed, however, the peripheral wavelength discrimination functions departed from the foveal functions at wavelengths greater than 560 nm. Peripheral functions derived from data obtained at 12 minutes and beyond following the bleach showed a decrease in disciminability for wavelengths longer than 560 nm; 480-540 remained unchanged by the experimental manipulations.
Rod signals decrease our ability to discriminate middle- and long- wavelength stimuli presented to the peripheral retina, but do not affect short-wavelength discrimination. Comparisons of the discrimination functions from the seven time periods following the bleach indicate the effect of rods abruptly appears at approximately 12 minutes post bleach. Furthermore, the pattern of results suggests that the rod effect on wavelength discrimination cannot be modeled in terms of a simple reduction in saturation.Abramov, I. Gordon, J. and Chan, H. (1990) Perceiving, Measuring and Using Color. Proceedings of the SPIE, 1250, 40-51.
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