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PubMed1997

Projected color slides as a method for mass screening of red-green color deficient individuals.

University students (111, both male and female) were screened for red-green color deficiency using projected 35 mm slides reproduced from Ishihara and H-R-R color plates. Ishihara and H-R-R color plates were tested in the same individuals at a second setting and the responses compared: 6.3% of the students were identified as color deficient by the Ishihara and 80.2% by the H-R-R projected slides while 5.4% were designated color blind by the Ishihara plates and 4.5% by the H-R-R plates. The sensitivity of both screening systems was 100%; the specificity of the Ishihara slides was 98.1% compared to only 20.8% for the H-R-R. The 9.8% prevalence of red-green deficiency detected by the Ishihara plates and 8.2% by the H-R-R plates for males is similar to the 6 to 9% frequency found for Caucasian males in other population studies. Within rigid guidelines, projected color slides have potential usefulness as a screening method for detecting individuals with red-green color deficiencies.

Adult↗

PubMedDate not supplied

Color distribution and visual color assessment of human gingiva and mucosa: a systematic review of the literature.

PURPOSE: This study undertook a systematic overview of the literature on the description and visual measurement of gingival color. MATERIALS AND METHODS: Two research questions were formulated. The first addressed the description of gingival color, while the second aimed at visual color measurement techniques. An electronic search was performed in 22 literature databases. The electronic search was complemented by hand searching. The retrieved articles were independently reviewed by two members of the research team. The levels of evidence of the articles were classified following the guidelines of the Oxford Centre for Evidence-Based Medicine. RESULTS: Of the nine articles retrieved by the two searches, six applied to the first question, two applied to the second question, and one applied to both questions. Three articles were published in Japanese and dealt with the color of gingival and alveolar mucosa. The clinical studies showed that the intraoral tissues of younger persons are of a lighter color. Evidence levels were no higher than 4. CONCLUSION: Studies on the description of gingival color used a narrative approach. Studies on visual gingival color measurement had diverse aims, methods, and parameters. It is impossible to compare or even combine their outcomes in a scientifically meaningful manner. Since none of the investigations used a controlled or randomized design, they represent low levels of evidence.

Color↗

PubMed1988

Molecular basis of abnormal red-green color vision: a family with three types of color vision defects.

The molecular nature of three different types of X-linked color-vision defects, protanomaly, deuteranomaly, and protanopia, in a large 3-generation family was determined. In the protanomalous and protanopic males the normal red pigment gene was replaced by a 5' red-3' green fusion gene. The protanomalous male had more red pigment DNA in his fusion gene than did the more severely affected protanopic individual. The deuteranomalous individual had four green pigment genes and one 5' green-3' red fusion gene. These results extend those of Nathans et al., who proposed that most red-green color-vision defects arise as a result of unequal crossing-over between the red and green pigment genes. The various data suggest that differences in severity of color-vision defects associated with fusion genes are caused by differences in crossover sites between the red and green pigment genes. Currently used molecular methodology is not sufficiently sensitive to define these fusion points accurately, and the specific color-vision defect within the deutan or protan class cannot be predicted. The DNA patterns for color-vision genes of female heterozygotes have not previously been described. Patterns of heterozygotes may not be distinguishable from those of normals. However, a definite assignment of the various color pigment gene arrays could be carried out by family study. Two compound heterozygotes for color-vision defects who tested as normal by anomaloscopy were found to carry abnormal fusion genes. In addition, a normal red pigment gene was present on one chromosome and at least one normal green pigment gene was present on the other.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Southern↗

PubMed2003

Coloring an action: intending to produce color events eliminates the Stroop effect.

The implications of an ideomotor approach to action control were investigated. In Experiment 1, participants made manual responses to letter stimuli and they were presented with response-contingent color patches, i.e., colored action effects. This rendered stimuli of the same color as an action's effect effective primes of that action, suggesting that bilateral associations were created between actions and the effects they produced. Experiment 2 combined this set-up with a manual Stroop task, i.e., participants responded to congruent, neutral, or incongruent color-word compounds. Standard Stroop effects were observed in a control group without action effects and in a group with target-incompatible action effects, but the reaction time Stroop effect was eliminated if actions produced target-compatible color effects (e.g., blue word --> left key --> blue patch). Experiment 3 did not replicate this interaction between target-effect compatibility and color-word congruency with color words as action effects, which rules out semantically based accounts. Theoretical implications for both action-effect acquisition and the Stroop effect are discussed. It is suggested that learning action effects, the features of which overlap with the target, allows and motivates people to recode their actions in ways that make them more stimulus-compatible. This provides a processing shortcut for translating the relevant stimulus into the correct response and, thus, shields processing from the impact of competing word distractors.

Color Perception↗

PubMed2006

Color congruity effect: where do colors and numbers interact in synesthesia?

The traditional size congruity paradigm is a Stroop-like situation where participants are asked to compare the values of two digits and ignore the irrelevant physical sizes of the digits (e.g., 3 5). Here a color congruity paradigm was employed and the irrelevant physical sizes were replaced by irrelevant colors. MM, a digit-color synesthete, yielded the classical congruity effect. Namely, she was slower to identify numerically larger numbers when they deviated from her synesthetic experience than when they matched it. In addition, the effect of color on her comparative judgments was modulated by numerical distance. In contrast, performance of non-synesthetes was not affected by the colors. On the basis of neurophysiological studies of magnitude comparison and interference between numerical and physical information, it is proposed that the interaction between colors and digits in MM occurs at the conceptual level. Moreover, by using the current paradigm it is possible to determine the stage at which color-digit binding in synesthesia occurs.

Adult↗

PubMed2000

Failure to detect changes in color for lines rotating in depth: the effects of grouping and type of color change.

A new technique for measuring change detection was introduced in which contours rotating in depth around a vertical axis (in a computer display) could be altered in color as they passed through their point of minimum extension (the median plane) where a thin static vertical occluder hid the change. Sets of five or six contours were either strongly grouped (similar in length, orientation and spacing) or weakly grouped (of variable length, orientation and spacing). Changes consisted of one line changing to a new color or else two lines swapping colors. The measure was the proportion of missed changes. When subjects were not instructed to look for change almost no changes were reported although subjects were told beforehand that they would have to describe the configuration after viewing it. When subjects were instructed to look for changes, it was found that detection of color change was significantly better for strongly grouped lines. It is proposed that grouping, by reducing redundancy, also reduces attentional demands with respect to the properties on which it is based, making it easier to attend to and therefore detect changes in other properties. We found that it was much easier to detect the introduction of a new color than to detect a swap between two existing colors. It is hypothesized that swap-type changes were harder to detect because they required attention to a conjunction of position and color.

Adult↗

PubMed1987

Color performance of video endoscopes: quantitative measurement of color reproduction.

We have conducted a study aimed at testing the color performance of video endoscopes in quantitative terms for the first time. The video endoscopes investigated were from Fuji, Olympus, Toshiba/Machida, and Welch-Allyn. The tests were carried out with an opto-electronic color analyser using standardized color charts and a neutral grey chart. Hue and chroma of the reproduced colors were measured. The Olympus video endoscope reproduces the hue very well, showing only slight color desaturation. The Fuji video endoscope had a yellowish tint, whereas the picture obtained with the WA video endoscope produced an inhomogeneous picture with a pronounced red/purplish cast at the top of the screen and almost neutral reproduction at the lower half. The Toshiba video endoscope was the only one with a color chip, and reproduced hue fairly well, but its colors were weakly saturated.

Color↗

PubMedDate not supplied

Fox colors in relation to colors in mice and sheep.

Color inheritance in foxes is explained in terms of homology between color loci in foxes, mice, and sheep. The hypothesis presented suggests that the loci A (agouti), B (black/chocolate brown pigment) and E (extension of eumelanin vs. phaeomelanin) all occur in foxes, both the red fox, Vulpes vulpes, and the arctic fox, Alopex lagopus. Two alleles are postulated at each locus in each species. At the A locus, the (top) dominant allele in the red fox, Ar, produces red color and the corresponding allele in the arctic fox, Aw, produces the winter-white color. The bottom recessive allele in both species is a, which results in the black color of the silver fox and a rare black color in the Icelandic arctic fox when homozygous. The B alleles are assumed to be similar in both species: B, dominant, producing black eumelanin, and b, recessive, producing chocolate brown eumelanin when homozygous. The recessive E allele at the E locus in homozygous form has no effect on the phenotype determined by alleles at the A locus, while Ed, the dominant allele is epistatic to the A alleles and results in Alaska black in the red fox and the dark phase in the arctic fox. Genetic formulae of various color forms of red and arctic fox and their hybrids are presented.

Alleles↗

PubMed1992

Skin color measurements in terms of CIELAB color space values.

The principles of color measurement established by the Commission International d'Eclairage have been applied to skin and the results expressed in terms of color space L*, hue angle, and chroma values. The distribution of these values for the ventral forearm skin of a sample of healthy volunteers is presented. The skin-color characteristics of a European subgroup is summarized and briefly compared with others. Color differences between individuals were identified in terms of one, two, or all three color-space parameters. Because the method is quantitative and the principles internationally recognized, these color-space parameters are proposed for the unambiguous communication of skin-color information that relates directly to visual observations of clinical importance or scientific interest.

Adult↗

PubMed1993

Appearance of colored patterns: pattern-color separability.

We have measured how color appearance of square-wave bars varies with stimulus strength and spatial frequency. Observers adjusted the color of a uniform patch to match the color appearance of the bars in square-wave patterns. We used low-to-moderate square-wave patterns, from 1 to 8 cycles per degree (c/deg). The matches are not photoreceptor matches but rather are established at more central neural sites. The signals at the putative central sites obey several simple regularities. The cone contrast of the uniform patch is proportional to square-wave stimulus strength (color homogeneity) and additive with respect to the superposition of equal-frequency square waves containing different colors (color superposition). We use the asymmetric matches to derive, from first principles, three pattern-color-separable appearance pathways. The matches are explained by two spectrally opponent, spatially low-pass mechanisms and one spectrally positive, spatially bandpass mechanism. The spectral mechanisms that we derive are similar to luminance and opponent mechanisms that are derived with entirely different experimental methods.

Color Perception↗

PubMed1989

Lateralization differences for color-naming and color-matching in men and women.

The relationship between accuracy of color-naming and color-matching in both visual fields (LVF and RVF) as a function of sex was investigated. Subjects were 19 men and 15 women who ranged in age from 18 to 32 yr. Each subject was tested on both a color-naming task and a color-matching task presented tachistoscopically. Accuracy measures for each task were obtained separately for both left and right visual fields. A two-factor analysis of variance with repeated measures on one factor followed by a t test for simple main effects showed significant right visual-field advantage for the color-naming task, a significant sex main effect for the color-matching task (in the left visual field only), and a significant interaction of sex by visual field for the matching task. Men performed in a more strongly lateralized fashion on the color-matching task than did women, supporting the notion of greater lateralization among males.

Adolescent↗

PubMed2004

Explanation for neon color effect of chromatic configurations on the basis of perceptual ambiguity in form and color.

Under reflected light conditions, we observed a neon color effect in a van Tuijl-type pattern for 30 combinations by pairing CMY inks. The results cannot be fully explained by Bressan's proposal as follows: (1) the illusory colors for the six configurations contradicted her predictions, (2) strong effects were not presented for complementary color pairs, and (3) for four configurations, the colors of line segments assimilated into those of the inducing patterns. Thus, the author proposes an hypothesis that the visual system treats neon color displays as ambiguous figures in form and color. This proposal can explain both illusory colors of the illusory area and those of the line segments themselves.

Color Perception↗

PubMed1981

Children's color perception in relation to habitat and skin color.

Developmental color perception of negroid and caucasoid children in 3 societies is examined in relation to the theories that proximity to the equator and fundus pigmentation (as measured by skin color) reduce shortwave (blue-green) in comparison with long-wave perception. The 278 4- and 8-year-old native-born, urban, English-speaking children were from latitudes 6 degrees 27' N (Enugu, Nigeria), 17 degrees 18' N (Basseterre, Saint Kitts, East Caribbean), and 34 degrees 3' N (Los Angeles, Calif.). Equal numbers of boys and girls from middle socioeconomic homes were medically examined for normal nutritional status and near vision. Children were individually tested on the Gaines Color Perception Test. The results show that short-wavelength perception is less accurate than long-wave-length perception in all locations, but most of the variance is attributable to conditions of low value or chroma stimuli rather than to proximity to the equator. There were no significant differences between Nigerian, Saint Kittitian and California caucasoid children. In accord with the pigmentation theory, young California negroid children had less accurate short-wavelength color perception than California caucasoid children. However, Nigerian and Saint Kittitian negroid children's perceptual accuracy was at least as accurate as that of caucasoid children. Amount of pigmentation does not appear to be a universal variable in children's color perception. Socioeconomic status, nutritional variables, developmental growth of the eye, or controlled stimulus conditions of the present research could account for the lack of positive relationships between color perception and habitat or skin color.

Child↗

PubMed1995

Color vision and color pattern visual evoked cortical potentials in a patient with acquired cerebral dyschromatopsia.

We examined a 74-year-old man because of difficulty seeing green and the presence of prosopagnosia. His visual acuity was 0.8 in both eyes. He was not congenitally color blind, and there was no family history of color blindness. A left superior homonymous quadrantanopsia was found. The dyschromatopsia ws identical in both eyes. The patient showed red-green deficiency on testing with Ishihara plates a deutan defect with Tokyo Medical College plates, strong blue-yellow defects and medium red-green defects with Standard Pseudochromatic Plates II and a tritan defect with the Panel D-15. He failed the New Color separation test with scores of 160 and could not carry out the Farnsworth-Munsell 100-hue test, but his color naming test results were normal. Visual evoked cortical potentials to black-and-white checkerboard and color pattern reversal (Red and Blue-Green, Green and Red-Purple, Purple and Yellow-Green: isochromatic paired checks) stimuli were normal. Bilateral inferior occipital lesions were found by computed tomography and T2-weighted magnetic resonance imaging. Our findings suggested that luminance and color channels up to area 17 in our patient were intact. We believe that our patient's acquired cerebral dyschromatopsia is rare.

Aged↗

PubMed1981

The influence of selected light intensities on color perception within the color range of natural teeth.

A study was undertaken to evaluate the influence of light intensity on the ability to discriminate color differences within the color range of natural teeth. The results show that shade selection is not significantly affected within the range of 75 to 300 fc. Neither the specialty of the dentist nor the amount of time in practice appeared to be a factor in making color discriminations. However, 7 of the 50 dentists serving as subjects were found to be color defective, and a difference was found between their color discrimination abilities and those of normal persons. This suggests that color-defective dentists should obtain assistance when matching tooth shades.

Color↗

PubMedDate not supplied

Achromatic parvocellular contrast gain in normal and color defective observers: Implications for the evolution of color vision.

The PC pathway conveys both chromatic and achromatic information, with PC neurons being more responsive to chromatic (L-M) than to achromatic (L+M) stimuli. In considering the evolution of color vision, it has been suggested that the dynamic range of chromatic PC-pathway processing is tuned to the chromatic content of the natural environment. Anomalous trichromats, with reduced separation of their L- and M-cone spectral sensitivities, have diminished chromatic input to PC-pathway cells. Dichromats, with absent L or M cones, should have no chromatic input to PC-pathway cells. Therefore, the PC-pathway dynamic range of color defectives should be released from any constraint imposed by the chromatic environment. Here we ask whether this results in compensatory enhancement of achromatic PC-pathway processing in color defectives. This study employed a psychophysical method designed to isolate PC-pathway processing using achromatic stimuli. In a pulsed-pedestal condition, a four-square stimulus array appeared within a uniform surround. During a trial, one of the test squares differed from the other three, and the observer's task was to choose the square that was different. A four-alternative, forced-choice method was used to determine thresholds as a function of the contrast of the four-square array to the surround. Seven color defective and four normal observers participated. Results showed no systematic differences between normals and color defectives. There was no enhancement of achromatic processing as compensation for reduced chromatic processing in the PC-pathway system in color defectives. From physiological recordings, PC-pathway achromatic contrast gains of dichromatic and trichromatic New World primates and trichromatic Old World macaques have also been shown to be similar to each other. Our study and the animal studies imply that PC-pathway contrast gain parameters were regulated by factors other than the environmental chromaticity gamut, and may have arisen in a nontrichromatic common ancestor to both Old and New World primates.

Animals↗

PubMed1978

Dichromatic color language: "reds" and "greens" don't look alike but their colors do.

When protanopes or deuteranopes arrange the Farnsworth Dichotomous Test colors in order of similarity, they reveal their lack of red/green hue discriminations by alternating chips that the normal trichromat sees as reddish and greenish test colors. The dichromatic orderings follow a systematic variation in saturation of blue hues through neutral and into yellow hues as described by theory for each of the two types. Some dichromats who show the typical test behavior nevertheless use reddish and greenish hue terms appropriately when instructed to name the same test colors. Lightness cues are probably used by these dichromats in the naming task but ignored in the perceptual similarity task. Thus, unlike normal trichromats, who use similar names for perceptually similar colors, dichromats may use dissimilar names for perceptually similar colors. In this way they can achieve concordance with the normative language system despite its discordance with their impoverished color perceptions.

Color Perception↗

PubMed2006

Ocular hazards of the colors used during the festival-of-colors (Holi) in India--malachite green toxicity.

The objective of this study was to evaluate the nature of the colors used and their toxicity to the eye upon exposure to them during celebration of Holi (our festival-of-colors). Color powders and formulations were procured at random in and around Delhi during the festival. The green/bluish-green colors reported with the higher incidence of ocular toxicity were subjected for further evaluation. Eyewash fluid collected from the patients exposed to the colors was also subjected for analysis. This study was further extended to evaluate the corneal penetration of malachite green using goat cornea in perfusion chamber. In 16/18 color samples collected, malachite green or 4-[(4-dimethylaminophenyl)-phenyl-methyl]-N,N-dimethyl-aniline was detected at different concentrations. In the eyewash fluid of four patients, HPLC estimation confirmed the presence of malachite green at concentrations of 1.3, 0.18, 3.5 and 5.4 microg in 250 ml which was responsible for its reported toxicity. The in vitrotrans-corneal penetration studies did not show any detectable amount of malachite green in effluent fluid-in vitro tissue retention studies revealed that increasing the contact time increases tissue concentration. After 2 min of exposure, the tissue concentration was significantly higher. To conclude, malachite green was extensively used in our festival of Holi and has caused severe ocular irritation with epithelial defect upon exposure, though it did not penetrate through the cornea-further in vitro and in vivo studies are required on colors used in Holi.

Animals↗