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PubMed2005

The molecular basis of variation in human color vision.

Common variation in red-green color vision exists among both normal and color-deficient subjects. Differences at amino acids involved in tuning the spectra of the red and green cone pigments account for the majority of this variation. One source of variation is the very common Ser180Ala polymorphism that accounts for two spectrally different red pigments and that plays an important role in variation in normal color vision as well as in determining the severity of defective color vision. This polymorphism most likely resulted from gene conversion by the green-pigment gene. Another common source of variation is the existence of several types of red/green pigment chimeras with different spectral properties. The red and green-pigment genes are arranged in a head-to-tail tandem array on the X-chromosome with one red-pigment gene followed by one or more green-pigment genes. The high homology between these genes has predisposed the locus to relatively common unequal recombination events that give rise to red/green hybrid genes and to deletion of the green-pigment genes. Such events constitute the most common cause of red-green color vision defects. Only the first two pigment genes of the red/green array are expressed in the retina and therefore contribute to the color vision phenotype. The severity of red-green color vision defects is inversely proportional to the difference between the wavelengths of maximal absorption of the photopigments encoded by the first two genes of the array. Women who are heterozygous for red and green pigment genes that encode three spectrally distinct photopigments have the potential for enhanced color vision.

Color Perception↗
PubMed1995

[Congenital color vision deficiencies as a social problem].

Color vision standards for various occupations and schools have been greatly eased recently. However, if the trend is unaccompanied with proper advice for color defective persons, there is a risk of accidents such as occurred in the past when color vision standards had not been introduced, because the color vision defect is unchanged. In this context, the history of color vision standards and the color confusion by color defective persons in their daily life were reviewed. The collected data together with pathophysiological characteristics of defective color vision suggest that at least the following measures are necessary from a practical point of view: (1) By education and awareness, color defective persons can avoid errors in color in most cases. Therefore, ophthalmologists should inform them of their defects in childhood and give instructions on how to compensate for their disadvantages. (2) In public and occupational situations, all the information conveyed by color should include lettering or other forms of redundancy for the convenience of color defective persons.

Color Vision Defects↗
PubMed1976

Effect of tinted contact lenses on color vision.

This study was designed to investigate the effects of various contact lens tints on color vision. Color vision performance of eight subjects was evaluated with the Farnsworth-Munsell 100 Hue Test while each subject wore each of 13 differently tinted contact lenses. No significant differences in color vision were found with the various lenses. However, performance on the test was affected by repetition. Regardless of the lens tints tested, color discrimination for the blue quadrant of the 100 Hue Test was the poorest. Further research is needed to determine the effect of tinted contact lenses on scotopic and mesopic vision.

Adult↗
PubMedDate not supplied

Critical issues in the use and analysis of the Lanthony Desaturate Color Vision test.

The Lanthony Desaturate Color Vision test (D-15d) has been used to demonstrate the incidence of acquired color vision defects resulting from toxic exposure. The D-15d is a sensitive test designed to grade color deficiencies, but results can be difficult to interpret beyond the qualitative level, and the high incidence of errors reported for controls in some toxicology studies raises questions about how to effectively use this test. This article reviews standard administration of the test, physical determinants of performance, classification of acquired color vision defects, and methods of analysis that have been used to quantify results. The basis for a new method of analysis is discussed, illustrating the source of some characteristic errors, and recommendations are made for test protocols to attempt to more closely identify the type of color vision loss with the goal of identifying the site of toxicological insult.

Color Perception↗
PubMed1993

More than three different cone pigments among people with normal color vision.

A fundamental feature of normal color vision is that red and green lights can be mixed to appear identical with a monochromatic yellow light. Another characteristic of normal color vision is that people often disagree on the amounts of red and green needed in the mixture to exactly match the yellow. Comparison of such color vision differences with photopigment gene differences reveals that a serine/alanine polymorphism at amino acid position 180 of X-encoded pigments can account for this type of color vision variation. This amino acid change shifts the spectrum of the pigment produced by about 6 nm, a value that would predict a larger minimum color vision difference between individuals than is actually observed. This discrepancy can be explained if, counter to the Young-Helmholtz theory as the explanation of trichromacy, many people with normal color vision have more than three spectrally different cone pigments.

Base Sequence↗
PubMed2002

Color vision: how the cortex represents color.

Our understanding of how we see color has benefited from the long tradition of visual psychophysics. More recently, models and methods from psychophysics are guiding modern neuroimaging experiments on color vision. Combining the two techniques can lead to discoveries that neither can make alone.

Cerebral Cortex↗
PubMed1988

A quantitative scoring technique for panel tests of color vision.

Panel tests of color vision (eg FM100-Hue test) lack a common quantitative method for the scoring of cap arrangements. We describe a scoring method applicable to all panel tests that makes use of a novel technique to analyze test cap data, namely the calculation of a moment of inertia from the Color Difference Vectors (CDVs) of any arrangement pattern. Using the Farnsworth D-15 panel, as an example, we specify how to determine CDVs and demonstrate the benefits of calculating a moment of inertia for the analysis of these vectors. Moment of inertia analysis yields three factors which quantify cap arrangements: the first is the confusion angle which identifies the type of color defect; the second is the Confusion index (C-index) which quantifies the degree of color loss relative to a perfect arrangement of caps; and the third is the Selectivity index (S-index) which quantifies the amount of polarity or lack of randomness in a cap arrangement. A retrospective study on the result of 53 normal and 66 congenitally color defective observers is reported and provides normative data. We show that the technique differentiates between different types of color defect and provides useful clinical information regarding a loss of color vision. Likewise, a similar observation is made on a smaller sample of FM100-Hue results. A BASIC computer program is provided for anyone wishing to use the technique.

Adolescent↗
PubMedDate not supplied

Color vision in diabetic school children.

The color vision of 64 diabetic school children was studied. Acquired color vision defects due to diabetes could not be found in any of the children. Two of the children had a congenital red-green color vision defect. In the examination, three different pseudoisochromatic plate tests (Isihara, Standard Pseudoisochromatic Plates part 2, and Lanthony Tritan Album) were used as well as the Nagel anomaloscope and three different cap arrangement tests (Panel D 15, Lanthony Desaturated Panel, and Farnsworth-Munsell 100 hue). The plate tests and the anomaloscope examination were fast, reliable, and well accepted by the children. The cap arrangement tests took more time, and many of the children neither liked nor properly performed these tests. Twelve color dependent glucose strip tests for diabetes care at home were also studied. A few of the youngest school children made mistakes in interpreting the colors of these strips, although their color vision was normal.

Adolescent↗
PubMed2000

Color vision: putting it together.

Color vision depends on the visual system comparing signals that originate in different classes of cone photoreceptors. New work shows that the different classes of cones are not only distributed irregularly, but in different individuals they are present in very variable proportions. Surprisingly, this does not affect color vision.

Animals↗
PubMed1992

Color vision in dominant optic atrophy.

The color vision of seven patients with dominant optic atrophy in four different families was studied with the following color vision tests: the Standard Pseudoisochromatic Plates part 2, the Lanthony Tritan Album, the Velhagen Pflügertrident plates, and Farnsworth Panel D 15, the Farnsworth-Munsell 100 hue test, the Nagel anomaloscope, and the Besancon anomalometer. In the first family, the mother, one of the sons, and one of the grandsons were affected. The mother had a deutantritan defect; the son and the grandson both had an undefined red-green and a tritan defect. In the third family, the mother and the son were affected. Only the color vision of the son could be examined. He had a tritan defect. In the fourth family, the mother and the daughter were affected. Both had a deutan defect. In the diagnosis of dominant optic atrophy, it must be remembered that not only blue color vision defects occur, but that other kinds of defects are also possible.

Adult↗
PubMed1989

Color vision in the dog.

The color vision of three domestic dogs was examined in a series of behavioral discrimination experiments. Measurements of increment-threshold spectral sensitivity functions and direct tests of color matching indicate that the dog retina contains two classes of cone photopigment. These two pigments are computed to have spectral peaks of about 429 nm and 555 nm. The results of the color vision tests are all consistent with the conclusion that dogs have dichromatic color vision.

Animals↗
PubMed2002

The validity of the University of Waterloo Colored Dot Test for Color Vision Testing in adults and preschool children.

PURPOSE: Most color vision tests require a high level of cognitive ability and as such are problematic for preschool children and multiply challenged individuals. Our goal was to design a color vision test for these groups and evaluate the clinical utility for preschool children. METHODS: The University of Waterloo Colored Dot Test (UWCDot) for Color Vision Testing requires the subject to distinguish a colored disc from seven gray discs. The target disc was a Munsell color along the deutan, protan, or tritan confusion line with gray. The first phase estimated the sensitivity and specificity of the test for adults. Thirty-one adults with normal color vision and 21 adults with congenital red-green defects participated. In the second phase, the utility of the UWCDot test for screening preschool children was determined. Subjects were 281 males and 269 females aged 2.5 to 5 years with normal vision. Their color vision was also assessed with the Standard Pseudoisochromatic Plates, Part 1 (SPP1). RESULTS: The sensitivity and specificity of UWCDot for adults approached the values for the desaturated D-15 when subjective responses were scored. Monitoring fixational eye movements produced sensitivity and specificity values that were similar to the anomaloscope. After adjusting the scoring criterion for the preschool children by using the females as a control, 2.9% of the males were identified as red-green deficient, 1.8% were blue-yellow deficient, and 3.2% had an unclassified deficiency. By definition, 1% of the females failed the test. Counting fixational eye movements was not a useful scoring method in the preschool children. Comparisons with SPP1 indicated that the UWCDot uncovers approximately 35% of the individuals with definite red-green color vision defects. CONCLUSIONS: Our results indicate that the UWCDot is capable of detecting approximately 35% of the preschool children who have a congenital red-green color vision defect. These individuals are likely to have a more severe deficiency.

Adult↗
PubMed1986

Color vision defects in early diabetic retinopathy.

Four color vision tests were used to assess color vision in 51 insulin-dependent diabetic patients and 41 normal controls. Right and left eyes of diabetic patients, selected because they had minimal retinopathy, had significantly more color vision defects than controls on Lanthony desaturated D-15, Farnsworth-Munsell 100-Hue, and chromagraph tests. The 100-Hue scores were significantly higher in both right and left eyes of diabetic patients than in controls. There were no significant associations between presence or absence of a color vision defect and age, sex, age at onset, duration of diabetes, or its metabolic control.

Adult↗
PubMed1990

Color vision characteristics of visually impaired children.

A classroom assessment of color vision characteristics of children with low vision was conducted using a battery of tests. The results showed 75% of the children failed one or more tests, although only 24% had a moderate or severe color vision defect. Comparisons with the low vision clinic color vision assessment showed that many of the children were not identified as being color vision defective. Considering the use of color-coded information in education, greater emphasis on color vision evaluations in routine low vision examinations is recommended.

Child↗
PubMed1994

The contribution of ultraviolet and short-wavelength sensitive cone mechanisms to color vision in rainbow trout.

Color vision in rainbow trout was studied by characterizing the spectral sensitivity of single units in three areas of visual processing: optic nerve; optic tectum; and torus semicircularis. Sensitivity to medium wavelength stimuli was a common feature of all single units examined. Additionally, long wavelength sensitivity was found in all units that were not medium wavelength-only or monophasic. Ultraviolet and short-wavelength sensitivity was common in small, juvenile trout, with ultraviolet sensitive units found in the optic nerve and torus, and short wavelength sensitivity found in the optic nerve and tectum. The shorter wavelength inputs were excitatory and, if found in the same unit, synergistic. The most common type of unit in the trout tectum and optic nerve is trichromatic, with ON inputs from the long and short cone mechanisms and an OFF input from the medium mechanism. In contrast, goldfish color vision is dominated by L and M opponent units without S input. The segregation of ultraviolet sensitivity in the torus but not in the tectum relates to functional differences of these two areas. While the tectum serves the function of wavelength discrimination, ultraviolet inputs to the torus may contribute to prey detection and orientation.

Animals↗
PubMedDate not supplied

Two-year evolution of perchloroethylene-induced color-vision loss.

Progression of perchloroethylene-induced color-vision impairment was studied in 33 dry-cleaner workers at 12 establishments in Modena, Italy. In an initial survey, we evaluated exposure with personal passive samplers, and we assessed color vision with the Lanthony D-15 desaturated panel. Two years later, workers were reexamined. In 19 workers (subgroup A), exposure to perchloroethylene had increased (median of 1.7 ppm versus 4.3 ppm, respectively), whereas in the remaining 14 workers (subgroup B) exposure was reduced (2.9 ppm versus 0.7 ppm, respectively). Color vision worsened in subgroup A, but no vision changes were apparent in subgroup B. The results indicated that an increase in exposure during a 2-y period, even if slight, can cause color vision to deteriorate. A similar slight reduction in exposure did not lead to color-vision improvement; perhaps this lack of improvement resulted from (a) an insufficient reduction in exposure, (b) an insufficient reduction in duration of exposure, or (c) irreversible perchloroethylene-induced color-vision loss.

Adult↗
PubMed1996

Cone-specific measures of human color vision.

PURPOSE: To describe a new test of color vision (cone-specific contrast sensitivity) and to evaluate its sensitivity in comparison to standard clinical tests. METHODS: Cone-specific colored letter charts were generated by computer and displayed on a color monitor. Each chart consists of colored letters that are most visible at the top but that gradually fade into a gray background. Cone contrast varies systematically on each chart so that letters are visible to only one cone type (L, M, or S cone). Cone-specific letter contrast sensitivity was measured in 30 color normals and 13 subjects with hereditary color deficiency. Values were compared to standard measures of color vision. RESULTS: In color normals, mean log contrast sensitivity was approximately the same on L-cone (1.84 +/- 0.08 log contrast sensitivity) and M-cone (1.87 +/- 0.08) tests but was reduced on the S-cone test (0.89 +/- 0.15) because of the fewer number of S-cones in the human retina. Subjects with red color deficiency showed significantly reduced contrast sensitivity on the L-cone test but normal performance on M- and S-cone tests. Subjects with green color deficiency showed decreased contrast sensitivity limited to the M-cone test. When standardized relative to variability, cone contrast sensitivity identified color deficiency unequivocally in all subjects, whereas FM 100 hue error scores detected 9 of 13 subjects with color deficiency. CONCLUSIONS: Cone-specific contrast sensitivity provides a quantitative measure of normal color vision and indicates both type and severity of color deficiency. It is useful for diagnosing hereditary color deficiency and for monitoring early color vision loss in ocular and systemic disease.

Adult↗