Introduction
Color vision, lens
LENS
We assessed the effect of a contact lens that filters short-wavelength (SW) visible light on color appearance. These effects were modeled and measured by direct comparison to a clear contact lens. Sixty-one subjects were enrolled, and 58 completed as cohort; 31 were 18 to 39 years old (mean ± SD, 29.6 ± 5.6), 27 were 40 to 65 years old (50.1 ± 8.1). A double-masked contralateral design was used; participants randomly wore a SW-filtering contact lens on one eye and a clear control lens on the other eye. Subjects then mixed three primaries (including a short-wave primary, strongly within the absorbance of the test lens) until a perceived perfect neutral white was achieved with each eye. Color appearance was quantified using chromaticity coordinates measured with a spectral radiometer within a custom-built tricolorimeter. Color vision in natural scenes was simulated using hyperspectral images and cone fundamentals based on a standard observer. Overall, the chromaticity coordinates of matches that were set using the SW-filtering contact lens (Tinted filters are often used in photography to alter the color appearance of images. It has also been hypothesized (e.g., The light-filtering characteristics of the natural lens, tinted intraocular implants, and macular pigment are all relatively stable features of the eye. When filtering changes quickly, however, the system requires time to renormalize. SW-filtering contact lenses contains chromophores that intentionally absorb specific wavelengths (380–450 nm) of visible light. Chromophores that filter in this range have a yellowish hue or “tint” imparted to them when viewed against a white background. The test lens also contains a bluish compound to normalize the cosmetic acceptance of the lens, thus resulting in a slightly teal color. This should not be confused with “tinted” contact lenses that contain pigments or dyes for the purpose of changing cosmetic appearance or making a lens easier to see for handling. See Transmittance of the SW-filtering (orange) and control (blue) contact lenses.In this study, we assessed whether SW-filtering contact lenses would influence color appearance (as opposed to chromatic discrimination measured by tests such as the FM-100 hue test). Two approaches were used. The first was to measure color appearance using additive tricolorimetry where three color primaries (red, green, and blue) are mixed to achieve a perfect neutral white. Subject settings are plotted in CIE space as chromaticity coordinates. This type of geometric representation of color space allows specification of the appearance of any mixture of light, rather than its spectral composition, by specific coordinates. Disruptions from normal trichromatic color vision are represented as alterations in the relative amounts of the color primaries used to create a perfect perceived neutral white. Because each variable is on a continuous scale, even small alterations in color appearance can be assessed.Although it is informative to characterize the effectiveness of such filters using precisely controlled and calibrated stimuli, 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 filter on color perception in natural environments, we also modeled the visual responses of individual observers to light in the real world. Thus, as a complement to the aforementioned empirical study, we developed modeling tools that permit quantitative characterization of the effect of filters on the color vision of individually specified observers. We present summary statistics of the predicted effects of the tested SW-filtering lenses on the color vision of a standard observer for a series of hyperspectral images of natural scenes.