Discussion
lens on color perception, lens, color vision deficiencies
COLOR VISION DEFICIENCIES, LENS
The term “color” is used in many different ways across numerous fields, but, broadly, color is a perception. Unlike many perceptions, however, the perception of color can be very precisely quantified using the CIE colorimetry system. We used a tristimulus colorimeter along with a spectral radiometer and spectral computations based on color matching functions. Subjects were asked to mix three primaries to achieve a perfect white (a color sensation without hue). This was done on subjects wearing a SW-filtering test contact lens in one eye and a clear contact lens in the other. Based on this contralateral design of the clinical phase of our study, with 58 subjects younger and older, we found that subtle tinting of a contact lens in the violet/blue region of the spectrum did not alter color appearance values in normal trichromatic subjects. Note that we tested color vision monocularly using a contralateral design. Hence, it is possible that wearing the lens in both eyes using a between-subject design may have yielded different results. This, however, seems unlikely given the fact that color perception tends to be yoked (e.g., Tinting contact lenses has been suggested as a means of influencing chromatic discrimination (not color appearance) in patients with color vision deficiencies ((Upper left) Filter transmittance (orange) and the normalized S-cone responsivity with no lens (blue). (Upper right) Normalized S-cone responsivity after applying the transmittance functions of either the SW-filtering test (orange) or the clear control (blue) contact lens. (Bottom left) Spectral radiance of the blue primary filtered by the SW-filtering test (orange) and the clear control (right) contact lenses. The peak amplitude and wavelength of the best-fit Gaussian is shown at the top right. (Bottom right) Relative S-cone activation to the blue primary with the SW-filtering test (orange) and the clear control (right) contact lenses. The cumulative total relative S-cone activation is shown in the top right.Moreover, any functional impact of tinted lenses will be realized in the natural world through their effect on light in natural scenes. To estimate the impact of a SW-filtering lens on color perception in natural environments, we modeled the visual responses of individual observers to light in the real world. Summary statistics of the predicted effects of the tested tinted lenses on the gamut of colors available to a standard observer in a series of hyperspectral images acquired in natural scenes indicate that the SW-filtering lenses are expected to degrade L/(L+M) chromatic contrast by 0% to 0.1% on average and to degrade S/(L+M) chromatic contrast by between 3.6% and 8.2% on average. In summary, the SW-filtering lenses are generally not expected to change the gamut of color contrasts appreciably; however, substantial degradation of S/(L+M) contrast is expected in a minority of scene content.Evidence in the literature supports the notion that visual adaptation occurs over multiple time scales (