Color Deficiency Research Articles

Clinical use of the City University test (2nd Edition)

The City University test (TCU test) aims to identify people with significant colour deficiency and to Classify the type of defect. 222 people with congenital red-green colour deficiency, diagnosed with the Nagel anomaloscope, were examined with the TCU test (2nd Edition). All deuteranopes and 44% of deuteranomalous trichromats failed the TCU test. Deutans who failed could be subdivided into two categories of severity depending on whether errors were made on five or more plates. 96% of protanopes and 26% of protanomalous trichromats failed. Protans made fewer errors than deutans and subcategories of severity could not be distinguished according to the number of errors made. The Farnsworth D15 test was found to be more effective than the TCU test in identifying significant protan colour deficiency. Detection and classification rates varied on all the plates of the TCU test. Mixed protan and deutan classification errors were made by 61% of subjects with the majority result correct in 80%. The most efficient plates are identified and recommendations are made for the optimum use of the TCU test in clinical practice.

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.

Overexpression of Human Stem Cell Factor Impairs Melanocyte, Mast Cell, and Thymocyte Development: A Role for Receptor Tyrosine Kinase-Mediated Mitogen Activated Protein Kinase Activation in Cell Differentiation

AbstractStem cell factor (SCF) is synthesized as both soluble (S) and membrane-associated (MA) proteins. Indirect insight into the function of MA and S isoforms of SCF has come from studies performed in Steel (Sl) mutant mice. However, the physiologic role(s) of these two isoforms remain unknown. In an attempt to better understand the in vivo role of c-kit/SCF interactions on various cell lineages, transgenic mice were generated that overexpress MA isoform of human SCF (hSCF). In murine cells, hSCF behaves as an antagonist to normal SCF function, due to interference with the interaction between endogenous murine SCF and its receptor, c-kit, encoded by the dominant white spotting (W) gene. Mice expressing the hSCF transgene display a variety of phenotypic abnormalities, which are accentuated when combined with W alleles. Here we show that mice homozygous for the hSCF transgene demonstrate a coat color deficiency seen in some mice homozygous for mild W alleles. Specifically, homozygous hSCF transgenic mice (hSCF220) display a pronounced forehead blaze, with additional white spots over the cervical region, as well as a very large belly spot. Doubly heterozygous animals that carry both a mutated W allele and the hSCF transgene also display an unusual pigment defect and a dramatic reduction in the number of dermal mast cells. Furthermore, overexpression of MA hSCF in the thymus results in abnormal thymocyte differentiation and proliferation, which is associated with reduced mitogen activated protein (MAP) kinase activation. Thus, MAP kinase activation by a receptor tyrosine kinase, such as c-kit, may be critical for the differentiation of thymocytes in vivo.

Efficiency of the Ishihara test for identifying red-green colour deficiency

The Ishihara test is the most widely used screening test for red-green colour deficiency. Results obtained by 401 people with red-green colour deficiency show that the combined sensitivity of the Transformation and Vanishing plates of the 38 plate Edition of the Ishihara plates is 95.5% on eight errors, 97.5% on six errors and 99.0% on three errors. The Hidden digit designs only identified approximately 50% of colour-deficient subjects. The protan/deutan classification plates were found to be more effective for deutans than for protans. No classification was obtained for 18% of protanopes and 3% of deuteranopes who saw neither figure on classification plates; 40% of protanomalous trichromats and 37.5% of deuteranomalous trichromats saw both classification figures and were classified on the relative luminance (clarity) of these figures. The specificity of the Ishihara test was determined in a previous study (Birch and McKeever, 1993) and the results combined with the present data to obtain the overall efficiency of the Ishihara plates for a representative cross section of colour-deficient subjects.

Efficiency of the Ishihara test for identifying red-green colour deficiency

Efficiency of the Ishihara test for identifying red-green colour deficiency

Efficiency of the Ishihara test for identifying red-green colour deficiency

Efficiency of the Ishihara test for identifying red-green colour deficiency

Clinical use of the American Optical Company (Hardy, Rand and Rittler) pseudoisochromatic plates for red-green colour deficiency

The efficiency of the American Optical Company (Hardy, Rand and Rittler) (HRR) plates for screening, grading and classifying red-green colour deficiency was examined for 401 male colour deficient subjects previously identified and diagnosed with Nagel anomaloscope. There were 83 protanopes, 30 protanomalous trichromats, 96 deuteranopes and 192 deuteranomalous trichromats. Screening sensitivity was found to be 100% for dichromats and 96.4% for anomalous trichromats based on one screening error (35 subjects, including 7 dichromats, where identified by a single error). Thirty subjects (13.5%) made errors on screening plates only and were identified as having minimal colour deficiency. The HRR grading system did not distinguish dichromats and anomalous trichromats; 54% of dichromats were graded as having moderate rather than severe colour deficiency. Protan/deutan classification was correct for 95% of subjects who failed grading plates. HRR grades for anomalous trichromats were compared with the anomaloscope matching range and with pass or fail of the D15 test. The results show that only two rather than four grading categories can be distinguished by the HRR plates and that both the D15 and the HRR plates are needed in a vocational test battery to establish the severity of colour deficiency.

Clinical use of the American Optical Company (Hardy, Rand and Rittler) pseudoisochromatic plates for red-green colour deficiency

Clinical use of the American Optical Company (Hardy, Rand and Rittler) pseudoisochromatic plates for red-green colour deficiency

Clinical use of the American Optical Company (Hardy, Rand and Rittler) pseudoisochromatic plates for red-green colour deficiency

Clinical use of the American Optical Company (Hardy, Rand and Rittler) pseudoisochromatic plates for red-green colour deficiency

Clinical use of the American Optical Company (Hardy, Rand and Rittler) pseudoisochromatic plates for red-green colour deficiency

Clinical use of the American Optical Company (Hardy, Rand and Rittler) pseudoisochromatic plates for red-green colour deficiency

Prevalence of congenital color deficiencies in secondary-school students in Tehran.

A population-based study was conducted to determine the prevalence of color deficiencies in secondary-school students (ages 12-14) in Tehran. A total of 2,058 students (1,136 males, 922 females) were examined with Ishihara pseudoisochromatic color plates. In the study population, 97 cases of defective color vision were detected, including 93 males and 4 females. The affected individuals all had negative histories of previous systemic and ocular disease or chronic use of medications. The visual acuity was 20/20 and the fundus was normal in all affected students. Of the 93 cases of defective color vision in males (8.18%), 56 cases (4.93%) involved deuteranomaly, 13 (1.14%) protanomaly, 13 (1.14%) deuteranopia, and 11 (0.97%) protanopia. The four cases in females (0.43%) involved deuteranomaly in three cases (0.32%) and protanomaly in 1 case (0.11%). Deuteranopia and protanopia were not detected in females. This is the first study to determine the prevalence of congenital color blindness in Iran. The results agree with reports of prevalence of congenital color blindness from Western Europe.

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 35mm 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.

THE USE OF COLOR IN THE SCIENTIFIC VISUALIZATION OF ACOUSTICAL PHENOMENA

Color is commonly used in representing scientific data, especially as color output devices have become widely available. The misuse of color can lead to confusing or even misleading representations of data. The purpose of this paper is to provide a review of guidelines for using color effectively, specifically aimed at the computational acoustics community. The question of whether or not to use color at all is initially raised, and gray-scale is suggested for appropriate cases. Human color deficiencies in technical audiences are then described, and the consequential choices of equally-accessible color schemes are discussed. The topics of human color perception models, hypsometric tints, contoured plots, and histogram equalization are introduced. Color palettes specifically suited for acoustical phenomena, such as linear and dB magnitudes, scales for positive and negative data, circular palettes for phase, and methods for illustrating different classes of phenomena (e.g., wave types) on a single plot, are discussed in detail. Color examples and Mathematica code are provided, and final recommendations are made for choosing effective color schemes.

Colour vision requirements of firefighters.

To perform their job safely firefighters must be able to identify colours on industrial gas cylinders, portable fire extinguishers, road traffic signals and several pieces of firefighting equipment. Although good colour vision is necessary we believe that the existing colour vision standard, which bars entry to the fire service to applicants who fail more than two plates of the Ishihara test, is unnecessarily stringent. We have identified and quantified the colour coded information encountered by firefighters. Colours were plotted on the CIE chromaticity diagram (1931) and isochromatic zones, which document the colour confusions of colour deficient observers, superimposed. This novel technique established possible colour confusions in different types of colour deficiency. Analysis of the results showed that red/green dichromats (protanopes and deuteranopes), severe deuteranomalous trichromats who fail the Farnsworth D15 test, and protanomalous trichromats are unsuitable for firefighting work. However, people with slight deuteranomalous trichromatism who pass the D15 test, are not disadvantaged and can be employed safely as firefighters. A new colour vision standard and a new testing procedure is recommended.

Does occupational exposure to argon laser radiation decrease colour contrast sensitivity in UK ophthalmologists?

The objects of the study were to determine: (1) whether United Kingdom ophthalmologists who used argon lasers had the elevation of colour-contrast thresholds previously discovered and (2) whether other users of argon lasers showed any unusual loss of colour vision. A total of 1072 UK ophthalmologists filled in a questionnaire about their professional use of lasers, the length of time spent operating, and their out-of-doors activities. Their colour vision was then tested by a new sensitive system, and if any abnormality was detected, a clinical eye examination was performed. The results were as follows: (1) Colour vision testing was shown to be reliable. Any self-selection bias was excluded. Test-retest variability was small. Normal results did not change during the survey. (2) A number of men with high red-green thresholds were discovered. Some were aware of their congenital insensitivity. The frequency of all such defects was less than the known incidence of congenital colour deficiency in the male population. (3) Additionally a number of high tritan (blue-yellow) thresholds were encountered, some associated with reported diabetes and hypertension. In other cases of this type, undetected or unacknowledged systemic disease may be present. (4) After making allowance for all these incidental causes of loss of colour vision, and for the effect of age on colour vision (which is very small) only four of the sample were > 2 SD above normal. (5) However, the average blue-yellow thresholds of ophthalmologists were slightly and highly significantly raised compared with normal, in the first year of the survey. During the second and third years, the mean thresholds declined to normal. Similar but less significant findings were found for protan thresholds. It is concluded that the enhanced safety precautions recently introduced are associated with a recovery of colour vision in this population, demonstrating that any changes to individuals were reversible. Colour vision screening has proved able to detect mild ocular abnormalities due to systemic and congenital disease.

Hermann von Helmholtz (1821-1894). On the 100th anniversary of his death

In Helmholtz's judgement it was a favourable fate to have been thrown under medical students and into medicine with a sense of geometrics and with knowledge of physics. The result of this favourable combination was the invention of the ophthalmoscope and the Handbook of Physiologic Optics. Those were the foundations of all physiological aspects of ophthalmology, which were taken up and completed by A. v. Graefe and his colleagues. The ophthalmoscope was invented on the occasion of his university-courses, when Helmholtz tried to explain the theory of the red reflex of the pupil. Stimulated by Helmholtz in the following year Ruete developed the method of indirect ophthalmoscopy. This method at once was simplified again by Helmholtz in an extraordinary way. These two publications by Helmholtz contain all further developments involved with the ophthalmoscopy as an anticipation. The Handbook of Physiologic Optics is the first encyclopedic monography of this topic. Many new inventions are extremely valuable for the practical requirements of ophthalmologists. The first chapter about dioptrics contains the description of the Ophthalmometer, a new instrument to measure the astigmatism. In the chapter about visual sensations a clear survey about light- and colour sense is given. The colour deficiencies which were found during the decades before are introduced as the most important arguments for the three-component-theory of human colour vision. The prototype of a telestereoscope is demonstrated in the third chapter about visual perception.(ABSTRACT TRUNCATED AT 250 WORDS)

Luminance noise and the rapid determination of discrimination ellipses in colour deficiency

A computer-controlled test of colour vision is described, in which luminance noise and masking contours are used to ensure that the subject's responses depend on chromatic signals. The test avoids the need--common to most computer-controlled tests--to define equiluminance for the individual subject before the colour test itself can be administered. The test achieves a good separation of protan and deutan subjects and reveals the large range of chromatic sensibilities among anomalous trichromats. As a population, dichromats had higher thresholds on the tritan axis of the test than did normals. In an extension of the test, full discrimination ellipses were measured for normal and colour-deficient observers. The nature of anomalous trichromacy is discussed and the possibility is raised that hybrid genes, resulting from genetic recombination, may code for incorrectly labelled or functionally impaired molecules.

A study of women heterozygous for colour deficiencies

We have examined the colour vision of 43 female subjects in the age range 30–59 yr of whom 31 were obligate carriers of various forms of colour deficiency and the rest were women who had no known colour-deficient relatives. In the case of all the carriers we established the phenotypes of their colour-deficient sons. As a group, carriers made significantly more errors on the Ishihara plates and showed enlarged matching ranges on the Nagel anomaloscope, but we could not replicate earlier reports of increased error scores on the Farnsworth-Munsell 100-Hue test or of systematic shifts in Rayleigh match mid-points. We did find that the colour matches of carriers of deuteranomaly were significantly displaced from those of normals in a ratio-matching task in which a mixture of 546 and 600 nm was matched with a mixture of 570 and 690 nm. Owing to X-chromosome inactivation, women who are heterozygous for anomalous trichromacy ought to have at least four types of cone in their retinae and we ask whether this affords them an extra dimension of colour vision, by analogy to New World monkeys where heterozygous females gain trichromacy in a basically dichromatic species. Many carriers of anomalous trichromacy exhibited no evidence for tetrachromacy, in that they accepted large-field Rayleigh matches following a rod bleach and they were unable to set unique matches in our ratio-matching task. However, eight carriers of anomalous trichromacy—and no other subject—refused large-field Rayleigh matches; and we found one carrier of deuteranomaly who was apparently able to make unique matches in the ratio-matching task.

Survey of the accuracy of new pseudoisochromatic plates

The accuracy of three new pseudoisochromatic tests for detecting red-green colour deficiency was assessed. These were the Ishihara plates, the Ishihara test for 'unlettered persons' and Ohkuma's test cards. We examined 500 subjects; 471 normal trichromats and 29 colour-deficient people. Results obtained for the 1989 edition of the Ishihara plates were compared with the 9th edition and the most efficient plates identified. Although normal trichromats may be expected to make several interpretive misreadings, the Ishihara plates were found to be superior to the 9th edition and to the Ohkuma test (1986) for colour vision screening. The new symbol designs of the Ishihara plates for 'unlettered persons' (1990) were found to be very effective for colour vision screening, and a further study with young children is proposed. The 38 plate 1989 edition of the Ishihara test is recommended for use in clinical practice. The designs included in the concise 24 plate edition and the new abbreviated 14 plate edition are not selected from the point of view of accuracy and more reliable results are obtained if the full test is given or if the practitioner shows only the most efficient designs.

Study of color vision in fragile X syndrome

Various theories have been postulated to account for the unusual inheritance pattern observed in the fragile X syndrome. The recent finding of a secondary amplification of the fragile X mutation in the offspring of carrier females [Oberle et al., 1991; Yu et al., 1991] is consistent with a maternal imprinting process. Laird [1987] has proposed that the fragile X mutation blocks complete reactivation of a previously inactivated fragile X chromosome. We have tested whether or not such a localized block extends as far distal as the red/green color-vision complex at Xq28. We found no evidence of color-vision defects among 25 male subjects with the fragile X syndrome. A fragile X positive woman also had normal color vision, despite being an obligate carrier of her father's gene for red/green color blindness. We conclude that the fragile X gene does not affect the function of neighboring color-vision genes, nor does it affect their ability to compensate adequately for inherited color deficiency on the homologous X chromosome in females.