Color vision impairment was examined in patients with type 2 diabetes mellitus (DM2) without retinopathy. We assessed the type and degree of distortions of individual color spaces. DM2 patients (n = 32), and age-matched controls (n = 20) were tested using the Farnsworth D-15 and the Lanthony D-15d tests. In addition, subsets of caps from both tests were employed in a triadic procedure (Bimler & Kirkland, 2004). Matrices of inter-cap subjective dissimilarities were estimated from each subject's “odd-one-out” choices, and processed using non-metric multidimensional scaling. Two-dimensional color spaces, individual and group (DM2 patients; controls), were reconstructed, with the axes interpreted as the R/G and B/Y perceptual opponent systems. Compared to controls, patient results were not significant for the D-15 and D-15d. In contrast, in the triadic procedure the residual distances were significantly different compared to controls: right eye, P = 0.021, and left eye, P = 0.022. Color space configurations for the DM2 patients were compressed along the B/Y and R/G dimensions. The present findings agree with earlier studies demonstrating diffuse losses in early stages of DM2. The proposed method of testing uses color spaces to represent discrimination and provides more differentiated quantitative diagnosis, which may be interpreted as the perceptual color system affected. In addition, it enables the detection of very mild color vision impairment that is not captured by the D-15d test. Along with fundoscopy, individual color spaces may serve for monitoring early functional changes and thereby to support a treatment strategy.

A variety of light sources are used in museum environments where the main concern is to prevent damaging effects of the light on paintings. Yet, the visual impression of an artistic painting is strongly influenced by the intensity and spectral profile of the illumination. The aim of this work was to determine psychophysically the spectral profile of the illumination preferred by observers when seeing paintings dated from the Renaissance époque and to investigate how their preferences correlate with the color temperature of the illumination and with the chromatic diversity of the paintings. Hyperspectral images of five oil paintings on wood were collected at the museum and the appearance of the paintings under five representative illuminants computed. Chromatic diversity was estimated by computing the representation of the paintings in the CIELAB color space and by counting the number of nonempty unit cubes occupied by the corresponding color volume. A paired-comparison experiment using precise cathode ray tube (CRT) reproductions of the paintings rendered with several illuminant pairs with different color temperatures was carried out to determine observers' preference. The illuminant with higher color temperature was always preferred except for one pair where no clear preference was expressed. The preferred illuminant produced the larger chromatic diversity, and for the condition where no specific illuminant was preferred the number of colors produced by the illuminant pair was very similar, a result suggesting that preference could have been influenced by chromatic diversity.

The purpose of this study is to determine how the viewing distance affects the pass/fail results of the CN Lantern (CNLan). The CNLan is a color vision test designed for the railway industry. It presents 15 triplets of colored lights that could be any combination of red, green and yellow. The test was viewed from 4.6 m and 2.3 m. Sixty-seven color-defectives participated in the first part of the study. Sixty-six percent of the subjects repeated the experiment 10 days later. There was a significant (P < 0.05) decrease in the mean number of errors from 7.6 to 4.3 as the distance decreased. There was also a corresponding increase in the percentage of subjects who passed from 9.0% at 4.6 m to 20.9% at the 2.3 m viewing distance. None of the subjects who passed at the longer distance failed at the shorter distance. The replication results were statistically identical to the first session (P > 0.05). Decreasing the CNLan viewing distance by 50% does decrease the number of errors and increase the pass rate. This indicates that some color-defectives could work in the railway yards where the sighting distances for the signal lights are shorter than on the main track.

The original AO HRR color vision test has been considered by many as one of the best plate tests. It is still accepted by many governmental agencies for color vision certification. In their 1954 publication, Hardy, Rand, and Rittler stated that specially compounded inks were used for printing to avoid color changes with time. Fifty years later, it is both important and interesting to determine whether the wear and tear cause significant color changes. The chance finding of a never-used second edition offers an opportunity to evaluate the color changes. A GretagMacbeth Spectrolino spectrophotometer was used to measure the chromaticities of the never-used book, and an extensively used book. Four plates (#4, 7, 13, 16), selected randomly from the four red-green sections, were analyzed. The colored dots from each of the eight plates were plotted on a CIE chromaticity diagram. Isocolor lines were drawn to evaluate chromatic alignment. Chromaticities for plates #4 and 7 are significantly different between the two books. With regard to alignment with isocolor lines, the extensively used book is better than the never-used book for plate #4. There is significant misalignment on plate #7 for both books. Chromaticities for plates #13 and 16 are essentially identical between books, all with good alignment with isocolor lines. The overall comparison shows that the chromatic alignment characteristics of the extensively used book are not worse than the never-used book. Since colors in these plates have to be aligned with both the protan and deutan axes, any significant color changes would have disturbed this delicate requirement. The findings of many plates with good alignment, and the lack of differences on plates #13 and 16 between books, suggest that there are no significant color changes over time. Differences between books on plates #4 and 7 were likely the result of the original printing process.

A previous study identified a significant metamerism in the several editions of the Hardy-Rand-Rittler pseudoisochromatic plates (HRR) but did not proceed to quantify the consequences of that metamerism (Dain, 2004). Metamerism arises from two sources and is almost inevitable when a printed color vision test is reproduced in several editions. Metamerism has two consequences; these are illuminant/source-based changes in performance and changes in performance with observer (less well known) when assessing anomalous trichromats. This study addresses the effects of illuminant/source and observer metamerism on the fourth editions of the HRR. Groups of colors intended to lie on a dichromat confusion line generally remain on a confusion line when the source is changed. The plates appear to be resistant to each form of metamerism, perhaps because the features of the spectral reflectance are similar for figure color and background gray. As a consequence, the clinician needs to be less concerned about using a non-recommended source than was previously believed.

Recently, molecular biological techniques have presented new opportunities for addressing questions concerning the neural mechanisms involved in color coding, thereby rousing renewed interest in animal color vision testing. We have modified a computer-based assessment tool, the Cambridge Colour Test, to make it suitable for use with animals. Here, the validity and reliability of the testing method were evaluated using squirrel monkeys. Because the chromatic stimuli and the achromatic backgrounds of the test consist of dots that vary in lightness, the stimulus parameters can be adjusted so that animals are not able to use luminance differences to make correct discriminations. Thus, in contrast to methods used previously, this test does not require that time be spent equating the luminance of each chromatic stimulus examined. Furthermore, the computer video-display based design of the testing apparatus can be easily replicated and adapted for use with many species in a variety of settings. In the present experiments, the squirrel monkeys' behavioral results agreed with the predictions for their color vision based on genetic analysis and electroretinography (ERG) spectral sensitivity data. Repeated measurements were highly consistent. Thus, an adaptation of the Cambridge Colour Test provides a valid and reliable method for testing color vision in animals.