Color Deficiency Research Articles

Reply [to “Comment on ‘Color schemes for improved data graphics,” by A. Light and P.J. Bartlein”

By calling attention to the perception of data graphics among color‐impaired readers, we hoped to raise awareness of an even more prevalent phenomenon: the misuse of spectral, or “rainbow,” color schemes. David B. Stephenson is quite right regarding the incidence of different forms of color‐vision impairment, which varies among racial and ethnic groups and is much lower for females [Sharpe et al., 1999]. Our article highlighted simulations of the less common protanopia to dramatize the general peril of spectral schemes.Figure 1 shows simulations of spectral, diverging, and progressive color schemes as they might appear to readers with either of the most common forms of color deficiency Figures 1a and 1b illustrate why the adage “red and green should never be seen” is a good one. The simulations in the right‐hand column show how deuteranopes may find it difficult or impossible to distinguish between red and green.

Color discrimination in carriers of color deficiency

Color discrimination in carriers of color deficiency

Quantification of color vision with cone contrast sensitivity

Human color vision is based fundamentally on three separate cone photopigments. Hereditary color deficiency, which affects up to 10% of males, results from an absorption shift or lack of L or M cone phototoreceptors. While hereditary S cone deficiency is rare, decreased S cone sensitivity occurs early in eye disease, underscoring the importance of quantifying S cone function. Our purpose is to describe a novel approach for quantifying human color vision based on the photopigments of normal color vision. Colored letters, visible to a single cone type, are presented in graded steps of cone contrast to determine the threshold for letter recognition. This approach quantifies normal color vision, indicates type and severity of hereditary deficiency, and reveals sensitivity decrements in various diseases.

Quantifying variations in personal color spaces: Are there sex differences in color vision?

AbstractWe report a search for group differences in color experience between male and female subjects, focusing on the relative prominence of the axes of color space. Dissimilarity data were collected in the form of triadic (odd‐one‐out) judgments, made with the caps of the D‐15 color deficiency test, with lighting conditions controlled. Multidimensional scaling reduced these judgments to a small number of dimensional‐weight parameters, describing each subject's sensitivity to color axes, i.e., how much each axis contributes to the inter‐color dissimilarities perceived by each subject. Normal trichromatic subjects in two age bands were examined, teenagers and university students, and in both cases males placed significantly less weight on a ‘red‐green’ axis, and more on ‘lightness’. We consider the implications and possible explanations. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 128–134, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10232

Color adaptation for anomalous trichromats

AbstractIn this article, we propose a content‐based color adaptation method for color vision impairment, especially for anomalous trichromats, to improve color information accessibility. Color degradation caused by anomalous trichromacy is compensated in digital color content with a range of the visible spectrum corresponding to color deficiency characteristics. To verify the usefulness of the proposed method, we performed clinical experiments as well as computer simulations. The results of both the experiments and the simulations show that the proposed adaptation could convey better color information to anomalous trichromats. © 2004 Wiley Periodicals, Inc. Int J Imaging Syst Technol 14, 16–20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20002

Presenting surface colors on computer controlled CRT displays

It is well known that CRT displays have limited color presentation capability. In everyday cases the drawback mainly shows up in the DTP field where the color space of displays does not match the printers' color space thus the color presented on the display does not correspond completely to printed color. In the contrary case the aim is to present painted surface color on a computer display. Due to the narrow color space of CRT displays direct matching of colors that fall outside of the display's color space is impossible based on CIE xyY color system. When transferring surface colors to displays there are tasks for which not only color matching, but also spectral matching is vital. In "display as measuring device" type of tasks such as color deficiency diagnosis with painted tests transferred to computers, enabling maximal correspondence of both parameters is important because color deficiency is caused by spectral degeneration of the sensitivity of the eyes.

New Color Vision Tests to Evaluate Faulty Color Recognition

Purpose: To develop and assess new color vision tests to be used in evaluating faulty color recognition. Methods: We developed new color vision tests to evaluate faulty color recognition. The two types of color vision tests, designed to assess faulty color recognition in color vision deficiencies, are based on principles that are different from those of the conventional color vision tests. In the first test plate, the subject is asked to choose either a red, green, or gray line from among 10 lines that are randomly colored red, green, gray, yellow, or blue. The score is the difference between the number of correct answers and the number of incorrect answers. In the second test plate, the subject is asked to identify a total of 10 red azalea blossoms, which are dispersed among numerous green leaves. Seventy-five persons with congenital color deficiencies and 20 subjects with normal color vision were examined using these new test plates. Results: The scores differed significantly between dichromats and anomalous trichromats, and between anomalous trichromats and subjects with normal color vision. Conclusions: The new tests are easy to use, sensitive, and have good reproducibility for use in discriminating subjects with color vision anomalies. These tests reveal the faulty color recognition that occurs unconsciously in persons with color deficiencies, and are useful in judging the quantification of color vision required in their daily life and occupations.

Visual and spectrophotometric shade analysis of human teeth.

Due to interhuman differences in the perception of color, visual shade assessment of human teeth is lacking standardization that may be improved by the use of a spectrophotometer. In this study, we tested the hypothesis that spectrophotometric assessment of tooth color is comparable with human visual determination. On 30 patients, three operators with unreported visual color deficiency independently selected the best match to the middle third of unrestored maxillary central incisors, using a Vita Classical Shade Guide. The same teeth were measured by means of a reflectance spectrophotometer. In the human group, all 3 visual shade selections matched in only 26.6%. In the spectrophotometric group, all 3 shade selections matched in 83.3%. In 93.3%, Delta E values of visually assessed tooth shades were higher than spectrophotometrically assessed Delta E values (p < 0.0001). The results suggest that spectrophotometric shade analysis is more accurate and more reproducible compared with human shade assessment.

Impact of color blindness on recognition of blood in body fluids.

Since color blindness is a common hereditary X-linked disorder, the authors investigated whether color blindness affects the ability to detect the presence of blood in body fluids. Ten color-blind subjects and 20 sex- and age-matched control subjects were shown 94 photographs of stool, urine, or sputum. Frank blood was present in 57 (61%) of the photographs. Surveys were done to determine if board-certified internists had ever considered whether color blindness would affect detection of blood and whether an inquiry on color blindness was included in their standard medical interview. Color-blind subjects were significantly less able to identify correctly whether pictures of body fluids showed blood compared with noncolor-blind controls (P = .001); the lowest rate of correct identifications occurred with pictures of stool. The more severely color-blind subjects were significantly less accurate than those with less severe color deficiency. Only 2 (10%) of the 21 physicians had ever considered the possibility that color blindness might affect the ability of patients to detect blood, and none routinely asked their patients about color blindness. The authors conclude that color blindness impairs recognition of blood in body fluids. Color-blind individuals and their health care providers need to be made aware of this limitation.—Thomas J. Liesegang

The Dilemma of Color Deficiency and Art

No “major” painter is known to be color deficient. Are there truly no color deficient artists, or have they not been recognized? The historical literature cites criteria for recognizing color deficiency in artists, but they are hard to apply without knowing the intentions of an artist. The work and commentary of a color-deficient artist who works currently in Paris are presented as an example. He uses a limited palette of colors, based on advice from colleagues as much as his own perceptions, and he uses colors in ways that do not always fit with expectations for color deficiency. Biographies of earlier painters suggest that there were a few whose color sense was poor, but these painters used assistants to help. The color sense of others, such as the English landscape painter John Constable (1776–1837), has been questioned because of a preponderance of suspicious color, such as murky green. However, there are good reasons to doubt that Constable was color deficient. It is instructive to know how proven color deficiency has influenced an artist's style. When medical information is unavailable, the best advice for the diagnostically-inclined observer is just to enjoy the art.

Impact of color blindness on recognition of blood in body fluids.

Color blindness is a common hereditary X-linked disorder. To investigate whether color blindness affects the ability to detect the presence of blood in body fluids. Ten color-blind subjects and 20 sex- and age-matched control subjects were shown 94 photographs of stool, urine, or sputum. Frank blood was present in 57 (61%) of the photographs. Surveys were done to determine if board-certified internists had ever considered whether color blindness would affect detection of blood and whether an inquiry on color blindness was included in their standard medical interview. Color-blind subjects were significantly less able to identify correctly whether pictures of body fluids showed blood compared with non-color-blind controls (P =.001); the lowest rate of correct identifications occurred with pictures of stool (median of 26 [70%] of 37 for color-blind subjects vs 36.5 [99%] of 37 for controls; P<.001). The more severely color-blind subjects were significantly less accurate than those with less severe color deficiency (P =.009). Only 2 (10%) of the 21 physicians had ever considered the possibility that color blindness might affect the ability of patients to detect blood, and none routinely asked their patients about color blindness. Color blindness impairs recognition of blood in body fluids. Color-blind individuals and their health care providers need to be made aware of this limitation.

Use of the mollon-reffin minimalist color vision test with young children

Purpose: We evaluated the Mollon-Reffin Minimalist (M-R M) color vision test to determine how successfully young children can perform the task and to compare success rates with the American Optical Hardy Rand Rittler (HRR) test and a preferential-looking type test based on the F2 plates (the Pease-Allen color test [PACT]). Methods: Participants included 146 children (aged 3-10 years) and 32 older subjects (aged 11-39 years). The M-R M test uses 3 series of colored caps coinciding with protan, deutan, and tritan confusion axes, with 6 saturations along each axis. The observer must identify a single colored cap from gray caps of varying lightness. The PACT test consists of 2 cards with targets for detecting red-green and blue-yellow color deficiencies. The tester judges the location of the target on the basis of the child's looking and/or pointing responses. The HRR was performed according to standard instructions, although a more flexible scoring protocol was also used. Results: A significant difference in the children's performance between the “test” item of the 3 tasks emerged (Cochran Q test, P <.001): all children successfully completed the M-R M, 90% successfully completed the PACT, and 88% successfully completed the HRR. Few errors were made on the M-R M red-green series, even among children aged 3 to 4 years, although errors were made with the least saturated blue-yellow cap at all ages. Recommendations are made for the use of the M-R M with children. Conclusions: The M-R M test can be performed by young children and may prove to be especially useful for detecting and monitoring acquired color vision defects. (J AAPOS 2000;4:366-72)

A new colour vision test in a PC-based screening system

The most commonly used method to examine the ability of the visual system to discriminate colours and detect colour vision deficiencies is based on pseudoisochromatic plates, such as the Ishihara plates. We describe a computer-based method to determine red–green colour deficiencies based on an anomaloscope simulator, which gave good results in a study of red–green discrimination is studied. It was shown experimentally that this computer-based method discriminates between subjects with colour deficiencies and subjects without colour deficiencies.

A redesigned Farnsworth dichotomous B20 test

The Farnsworth dichotomous B20 test has been reconstructed using a circle of Munsell Hues with value 5: 7 hues have chroma 4, and 13 hues have chroma 2. Results were obtained for 46 normal subjects, 36 subjects with red-green colour deficiency, and 1 congenital tritanope. A larger number of deuteranomalous trichromats fail the reconstructed B20 than fail the Farnsworth D15 test. The B20 test gives good protan/deutan classification, when the test is failed, and provides significantly more isochromatic colour confusions for identifying and classifying tritanopia and tritan colour deficiency than the D15 test. © 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S253–S255, 2001

Color-vision variations represented in an individual-difference vector chart

The aim was to reconstruct a uniform color space that could accommodate normal and abnormal variations in color vision. Color-dissimilarity data were collected from normal trichromats and red-green deficients, using lights varying in spectral composition and luminance. The data were analyzed with an individual-differences multidimensional scaling program and resulted in a 3D group configuration. In addition, differences in saturation required a hemispherical representation for the “color plane,” with a 4th dimension obtained when a constraint of sphericity was included in the algorithm. Subject-specific color spaces were derived from this group configuration by axial compression, preceded by a rotation of the chromatic plane. In the spaces of color deficients, compression along a red-green axis occurred, though the direction of the compression differed for protans and deutans. The extent of the compression reflected the severity of abnormality. Transformations of the subject-specific color spaces — compression extent and the angle of rotation — were portrayed in a polar-coordinate chart. The chart separates normal trichromats from the red-green deficients, distinguishes protans from deutans, and quantifies the deficiency within each class. © 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S230–S234, 2001

Color spaces of color-normal and color-abnormal observers reconstructed from response times and dissimilarity ratings.

With multidimensional scaling analysis, color spaces were reconstructed from reaction times (RTs) required to make same-different judgements of pairs of 15 equiluminant colors and from dissimilarity ratings between them. In addition to normal trichromats, observers with red-green color deficiency were tested. Two main purposes were served by this study: (1) to compare spatial representations of colors derived from discriminative RTs with those derived from dissimilarity measures and (2) to examine whether the task may selectively affect the dimension reflecting, in color-abnormal spaces, the deficient red-green mechanism. Contradicting our hypothesis of lower dimensionality of RT spaces, as compared with rating spaces, no consistent differences in solution dimensionality were found. However, configurations derived from the two measures diverged. The rating procedure yielded the most logical results for recovering color space. The RT configuration revealed contraction in the tritanopic direction, indicating longer color processing when the short-wavelength mechanism is involved, and in addition, for color-abnormal observers, clustering in the protanopic and deuteranopic directions, indicating even longer processing by the deficient red-green mechanism. This finding implies that RTs are suitable for detecting temporal differences in color processing but, for that very same reason, rather ill-suited for reconstructing color spaces.

Applying the Ishihara test to a PC-based screening system

Aim: A commonly used method to examine the ability of the visual system to discriminate colours is based on isochromatic plates, such as the Ishihara plates. This article will introduce a computer-based method to determine red–green colour deficiencies based on presenting Ishihara plates using a CRT monitor. Method: The spectral emission of the reflected daylight of the plates was compared with the spectral emission of the plates presented on a CTR monitor. The screening efficiency of the Ishihara plates was assessed by testing 10 subjects with normal and 10 subjects with abnormal colour vision, using the Ishihara plates and using the computer-based approach. Results: It was experimentally shown that despite the differences between the spectral emission of the CRT monitor and the reflected daylight of the Ishihara plates, the computer-based method discriminates subjects with colour deficiencies from subjects without colour deficiencies. Conclusions: Using a CRT monitor for screening purposes, a reduced number of Ishihara plates is recommended to assess colour vision. The suggested method uses nine instead of 15 plates and a criteria of two not correctly detected plates to determine colour deficiency.

Acquired colour deficiency in patients with Parkinson’s disease

The blue cone pathway is reported to be affected early in Parkinson’s disease (PD) and acquired type three (tritan) defects may occur. Sixty-one patients attending a treatment and rehabilitation centre for PD were examined with clinical colour vision tests. Seven of 13 patients, for whom the diagnosis of PD was equivocal or who had other medical conditions, were identified as having tritan colour deficiency. Results for the remaining 44 PD patients were compared with 40 age matched controls. Ten PD patients (22.7%) had tritan defects. Tritan defects were not found in the control group but performance on some tests was age related. We conclude that clinical tests for tritan colour deficiency are unlikely to be helpful in identifying PD.

On derivation of spectral sensitivities of the human cones from trichromatic colour matching functions

Despite the recent advance made by using the direct methods of retinal densitometry, microspectrophotometry and suction electrophysiology, the psychophysical approach based on colour matching data still remains an important source of accurate information about the spectral sensitivity of the cone photoreceptors in the human visual system. However, the commonly used technique of estimating cone sensitivities, based on the assumption that dichromacy is caused by the lack of one of the three types of the cone photoreceptors, requires the colour matching functions not only from trichromatic observers but from dichromats as well. Here we evaluate an alternative approach, originally put forward by Bongard and Smirnov, that derives cone spectral sensitivities from colour matching functions only; without resorting to colour deficiency or any other data. When applied to CIE standard colour matching functions, this method yields curves of spectral sensitivities that are close to the classical Smith–Pokorny fundamentals, though the long-wave cone is shifted towards the short-wave region of the spectrum by 5 nm, as compared with Smith and Pokorny’s results.

The role of ternary projections in colour displays for geochemical maps and in economic mineralogy and petrology

Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation.