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PubMed1982

Improved color vision testing.

Pseudoisochromatic color vision testing plates have traditionally provided the clinician with screening-type information regarding the color with screening-type information regarding the color vision of patients. The introduction of a variable-color filter, through which the patient views these plates during testing, produces quantifiable results while exploiting the clinical advantages of the color plates. Thus, this approach allows the quick classification and quantification of color vision defects in a clinical setting. The results of this study on 153 subjects show that a variable-color filter combined with a series of traditional pseudoisochromatic plates can be successfully used on patients in a typical ophthalmology clinic to identify normal persons, protanopes, and deuteranopes. The results of the new test correlated well with those of standard tests.

Adult↗
PubMed2003

Color vision.

Many visual disorders produce acquired color vision defects. Color vision theory emphasizes several stages of visual processing: prereceptoral filters (lens, macular pigment, pupil), cone photopigments (L-, M-, and S-cones), and postreceptoral processes (red-green, S-cone, and luminance channels). Congenital color defects, which affect 8% to 10% of males and 0.4% to 0.5% of females, result from alterations in the photopigment absorption spectra or the absence of one or more photopigments. The most common defects are color vision deficiencies (protan and deutan defects), which are milder than the rarer achromatopsias (complete loss of color vision). Acquired color vision defects can be attributed to a number of different causes: alteration of prereceptoral filters, reduced cone photopigment optical density, greater loss of one cone type than the others, and disruption of postreceptoral processes. Acquired color vision defects have been divided into three classes: type 1, red-green defect with scotopization; type 2, red-green defect without scotopization; and type 3, blue defects (with or without pseudoprotanomaly). Blue defects are usually type 3 acquired defects because congenital tritan defects have an incidence of one in several tens of thousands. Red-green defects can be acquired or congenital, and ruling out acquired defects can require a battery of tests (plates and arrangement tests, anomaloscopy, perhaps genetic analysis). Color vision tests must be administered carefully (with a standard illuminant and protocol), and pupillary miosis or high lens density should be noted and their possible effects considered when interpreting test results. Plate tests provide a simple screening method but do not provide a diagnosis. Arrangement tests and anomaloscope testing take more time and make greater demands on the tester, but they provide a more thorough evaluation. When standard protocols are followed and results are interpreted in terms of prereceptoral filters, photopigment optical density, cone loss, and disruption of postreceptoral processes, a battery of color vision tests can be useful in the differential diagnosis, after progression of the disease, and for evaluating the effectiveness of treatment.

Color Perception↗
PubMed1993

[Examination of confusion loci in acquired color vision deficiency with surface color].

Miscellaneous color vision tests were performed on 66 eyes in 46 acquired blue-yellow deficiency cases, in which the deficiency resembled congenital tritanopia. The confusion loci converged at a point on the short wavelength side of the spectrum in central chorioretinopathy, diabetic retinopathy, branch retinal vein occlusion, retinal pigmentary degeneration, and macular degeneration. However, the confusion loci of glaucoma differed from those of the other 5 diseases of the retina. They crossed the purple boundary, showing a unique tendency among the diseases exhibiting acquired blue-yellow deficiency. In these diseases, except in chorioretinopathy, no correlation was observed between visual acuity, visual field and color confusion.

Adult↗
PubMed1989

[Examination of central vision. Visual acuity, contrast sensitivity, color vision].

In the neurophysiological organization of the visual system, form, color, movement, and depth perception are processed separately. Therefore, sensorial examination methods should test each of these basic functions separately, since they may be affected individually or to different extents by pathologic processes. For diagnosis the limit of visual acuity, i.e., the capacity for discrimination must be searched for, using Paliaga's "limits method". Visual acuity can also be tested in infants by the preferential looking method. Contrast sensitivity is tested using sinusoidal grid patterns of varying contrast and spatial frequency. In routine practice, however, this is usually achieved more easily with acuity cards on which contrast is reduced in several stages. The "two-equation method" is a colorimetric test combining two metameric matches, red + green = yellow, and blue + green = cyan, for testing color vision. The test requires an anomaloscope or anomalometer with four light channels. With this method it is possible to test the "red", "green", and "blue" cones and the "red-green" and "blue-yellow" opponents. The test provides a qualitative and quantitative evaluation of color vision disorders. If no colorimeter is available, classic printed test can be used. However, they might never achieve the same qualitative and quantitative precision.

Color Perception Tests↗
PubMed2004

Signatures of selection and gene conversion associated with human color vision variation.

Trichromatic color vision in humans results from the combination of red, green, and blue photopigment opsins. Although color vision genes have been the targets of active molecular and psychophysical research on color vision abnormalities, little is known about patterns of normal genetic variation in these genes among global human populations. The current study presents nucleotide sequence analyses and tests of neutrality for a 5.5-kb region of the X-linked long-wave "red" opsin gene (OPN1LW) in 236 individuals from ethnically diverse human populations. Our analysis of the recombination landscape across OPN1LW reveals an unusual haplotype structure associated with amino acid replacement variation in exon 3 that is consistent with gene conversion. Compared with the absence of OPN1LW amino acid replacement fixation since divergence from chimpanzee, the human population exhibits a significant excess of high-frequency OPN1LW replacements. Our results suggest that subtle changes in L-cone opsin wavelength absorption may have been adaptive during human evolution.

Africa↗
PubMedDate not supplied

[Physical models of color vision].

Models of color vision are discussed on the basis of determining the difference between the signals of sensors of white (rods) and color (cones) vision. It was shown that the whole optical spectrum (RGB) can be obtained, provided only two and four types of sensors are used within a three-component model of color detection. The described models provide for comprehensive explanations to extensive experimental data on color vision.

Color Perception↗
PubMed1994

Molecular basis for color vision.

Amino acid sequences of four kinds of chicken cone pigments and two kinds of nocturnal gecko visual pigment were determined. Calculations of amino acid identities indicate that gecko pigments should be cone pigments. A phylogenetic tree of visual pigments constructed demonstrated that cone pigments evolved earlier than rod pigments (rhodopsins), indicating that daylight vision including color vision appeared earlier than twilight vision. The divergence of cone pigments to rhodopsins would be caused by replacing basic amino acid residues to acidic ones according to net charge calculations. A comparison between chicken rhodopsin and cone pigments (chicken green and red) displayed that the cone pigments are faster in regeneration from 11-cis retinal and opsin, faster in formation of meta II-intermediate and shorter in lifetime of meta II-intermediate than rhodopsin. These facts would partly explain the rapid dark adaptation, the rapid light response and the low photosensitivity of cones compared with rods. In comparison with di- and tri-chromatic color visions, chicken tetra-chromatic vision was discussed on the basis of both absorption spectra of cone pigments and filtering effect of oil droplets.

Animals↗
PubMed1979

Clinical implications of color vision research.

The attributes of color and the mechanisms underlying normal and defective color vision are reviewed. The clinical implications of some research efforts bearing on congenital and acquired color defects, peripheral color vision, and the influence of photostable pigments on color vision and color vision tests is presented. This presentation is intended to illustrate how selected avenues of research have contributed to our understanding of color vision and to demonstrate the clinical utility of that research.

Color Perception↗
PubMed2004

Color vision testing.

The science of color vision testing has evolved since its inception in the late 1700s. Since then, the rudimentary technique of comparing color names has been replaced by more sophisticated methods. Commonly used tests in clinical practice today include isochromatic plates, arrangement tests, anomaloscopes, and lantern tests. Each category has unique attributes that make it suitable for a particular clinical situation. The clinician should be aware of the requirements for administering and grading each test type. Factors such as the quality of the illuminant and the size of the field of view are important elements in setting up a proper color vision laboratory. Currently, no treatment exists for congenital color vision defects. However, studies show that diagnosis of these defects early in life may help children adjust better to tasks at school and may help adults understand their limitations at work. Acquired color vision defects are often used as markers of ocular pathology in the clinical setting. Different color vision tests are appropriate for diagnosing the different categories of defects. Sometimes, a battery of tests may be appropriate. This paper is a review of the current knowledge in the field of color vision testing.

Color Perception↗
PubMedDate not supplied

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.

Color Perception↗
PubMed1995

Numbers and ratios of visual pigment genes for normal red-green color vision.

Red-green color vision is based on middle-wavelength- and long-wavelength-sensitive visual pigments encoded by an array of genes on the X chromosome. The numbers and ratios of genes in this cluster were reexamined in men with normal color vision by means of newly refined methods. These methods revealed that many men had more pigment genes on the X chromosome than had previously been suggested and that many had more than one long-wave pigment gene. These discoveries challenge accepted ideas that are the foundation for theories of normal and anomalous color vision.

Base Sequence↗
PubMed1999

Testability of a color vision screening test in a population with mental retardation.

PURPOSE: The purpose of this study was to determine the testability of the "Co or Vision Testing Made Easy" color vision test, marketed as a screening test for young children, in a population of individuals with mental retardation. The test uses simple geometric figures that are easily identified. Previously, the test has demonstrated validity as a measure of color deficiency. METHODS: The test was presented to Special Olympic athletes, who are individuals with mental retardation or significant developmental delay, at four sites: the 1997 World Winter Games in Toronto, Canada; the Texas Summer Games in Houston, Texas; the Massachusetts Summer Games in Boston, Massachusetts; and Regional European Swim Competition in Seville, Spain. The criteria for passing was 8 correct responses on the first trial or 9 of 9 on the second attempt. RESULTS: Testability in Toronto, Canada; Houston, Texas; and Seville, Spain was high--95.5%, 98.7%, and 95.7%, respectively. Testability, however, dropped to 78.8% during the Boston, Massachusetts screening. There was no apparent difference in the testing environment that would account for the difference. The overall rate of testability was 93.2% for the 1078 athletes screened. The frequency of males identified as color deficient was similar to that expected in the general population; only two females (in Spain) failed the color vision screening. CONCLUSIONS: The "Color Vision Testing Made Easy" color vision test was successfully completed by a very high percentage of Special Olympics athletes. These results suggest that this test is useful in screening this population for color deficiencies, and that the prevalence of color vision deficiencies is approximately the same in individuals with mental retardation as in the general population.

Adolescent↗
PubMed2000

Color vision and the four-color-map problem.

Four different colors are needed to make maps that avoid adjacent countries of the same color. Because the retinal image is two dimensional, like a map, four dimensions of chromatic experience would also be needed to optimally distinguish regions returning spectrally different light to the eye. We therefore suggest that the organization of human color vision according to four-color classes (reds, greens, blues, and yellows) has arisen as a solution to this logical requirement in topology.

Animals↗