Repeatability of the C‐100 colour vision test

Background: The C‐100 colour vision test has been shown to have a high validity for diagnosing the type of red‐green colour vision defect, however, there is little information on the repeatability of the test. This study examines the repeatability of the C‐100 in classifying the colour vision defect as either protan or deutan. Methods: The C‐100 was administered on two occasions to 58 subjects with congenital red‐green colour vision defects: The sessions were separated by a minimum period of 10 days. Results: The repeatability of the C‐100 was high with a kappa coefficient of agreement for diagnosis of 0.96. The few discrepancies were misclassifying protans as deutans. Conclusion: The C‐100 is a highly repeatable test in terms of separating protans from deutans. However, if a discrepancy occurs, it is more likely to be a protan misclassified as a deutan rather than vice versa.     

Does the Farnsworth D15 test predict the ability to name colours?

Background: The Farnsworth D15 test is designed to categorise colour vision deficiency as severe or moderate. The level of difficulty of the test was set so that those who passed it should be able to recognise surface colour codes, such as those used for electrical wiring. The test is widely used to provide advice to patients with abnormal colour vision and is often used for occupational selection when reliable recognition of surface colour codes is required. However, there has been only one previous study of the correlation between performance at the D15 test and the naming of surface colour codes and there has been no study of whether a person who passes the D15 can reliably name surface colours. Methods: One hundred and two people aged 11 to 65 years with abnormal colour vision were recruited from consecutively presenting optometric patients and were asked to name the colours of fabric, paint and cotton thread samples. There were 10 colours in each class of material and the samples were presented in a large (five to 10 degree angular subtense) and small size (2.5 deg and a single thread). The errors made were compared to those made by an age‐matched control group of equal size with normal colour vision. Results: The correlations between the Farnsworth D15 colour confusion index and colour naming errors were 0.62 for the large stimuli and 0.73 for the small stimuli. Its sensitivity and specificity identifymg those who made more errors than the worst performing colour normal person were 0.80 and 0.69 (large stimuli) and 0.75 and 0.71 (small stimuli). A Nagel anomaloscope range of less than 35 scale units provides essentially the same sensitivity and specificity. Conclusions: About 40 per cent of those with abnormal colour vision can name the main colours correctly under good visibility conditions. The D15 test is an imperfect predictor of those who can name surface colour codes correctly but it does provide useful information for general counselling. It is not suitable as a single test for occupational selection because it will pass 20 per cent who cannot name surface colours correctly and fail 30 per cent who can. In occupations in which recognition of surface colour codes is of critical importance, it may be best not to select people with abnormal colour vision because of the lack of a colour vision test that is a perfect predictor of the ability to recognise surface colours.     

An artist with extreme deuteranomaly

Background : There has been speculation about the colour vision of some artists of earlier generations based on the uncertain evidence of how they used colour, but it seems that no major artist has been shown to have a colour vision defect. A few lesser artists are known to have abnormal colour vision and its influence on their painting has been reported in the literature. However, there has been only one report of a deuter‐anomalous artist and no detailed report of one with extreme deuteranomaly. Methods : An amateur artist was diagnosed as having extreme deuteranomaly using standard clinical tests. He was interviewed about his difficulty with colour when painting and the strategies he used to counter these problems. His work was studied to determine the colour palette he used and he was set the task of copying another painting to determine the nature of any errors he might make. Results : The subject limits his palette to short‐wave blues and blue‐greens and longwave yellow, orange and red. He avoids use of yellow‐greens of which he is uncertain. He has adopted a few strategies that help him avoid mistakes in manipulating colour. Despite diese difficulties, he is able to create attractive paintings. His early work tended toward monochrome but in his later work he has been able to create warm colourful effects with a limited palette. Conclusion : Defective colour vision is a handicap in those artistic activities using colour but it is not an insurmountable barrier. Optometrists should counsel patients with a colour deficiency who are considering a career in the graphic arts about the difficulties they will encounter and the strategies they can use to help minimise those problems.     

Communication:Five cricketers with abnormal colour vision

Five cricketers with abnormal colour vision, all of whom had mild deuteranomaly, reported occasions when they had lost sight of the ball when the background was the green grass of the playing field or the green of grassy banks or trees surrounding the playing field. While these five cricketers demonstrate that mild deuteranomaly does not preclude playing cricket successfully at a competitive level, their responses to questions at interview suggest that those with more severe forms of abnormal colour vision may be at a disadvantage. This conclusion is consistent with the under‐representation of abnormal colour vision in a sample of first class county cricketers in England reported by Goddard and Coull (BMJ 1994; 309 1684–1685).     

Protan colour vision deficiency and road accidents

Background : Protans are precluded from holding a commercial driver's licence in Australia because they have a substantially reduced ability to see red lights and have more road accidents involving signal lights. This exclusion has been in place since 1994 but is likely to be abandoned following a current review of medical standards for commercial drivers. This paper reviews the level of risk of road accidents due to protan colour vision deficiency. It also addresses the question of whether it is fair to regard all protans as having a higher risk of road accident because some protans might have a sensitivity to red light that is as good as that of some people with normal colour vision. Methods : Data of two studies by Verriest and co‐workers are re‐analysed to estimate the degree of overlap of the protan and colour normal distributions of sensitivity to red light. Results : Field trial data show that protans have a very reduced visual range for red signals compared to colour normal observers but there is considerable variability among both classes of observers and the distributions do overlap. However, some variability is due to differences in observers' choices of a detection criterion, their speed of response and the measurement method. A laboratory study of the spectral sensitivity of protan and colour normal subjects that largely removes these sources' variability shows that all protans have a sensitivity to red light that is less than that of the least sensitive colour normal. Conclusion : It is reasonable to conclude that all protans, regardless of the severity of their defect, have a lesser ability to see red signals than colour vision normal observers and for that reason will have a higher risk of road accident.     

Using clinical tests of colour vision to predict the ability of colour vision deficient patients to name surface colours

PURPOSE: To determine the predictive power of commonly used tests for abnormal colour vision to identify patients who can or cannot name surface colours without error. METHODS: The colour vision of 99 subjects with colour vision deficiency (CVD) was assessed using the Ishihara, the Richmond HRR (2002), the Farnsworth D15, the Medmont C100 and the Nagel anomaloscope. They named 10 surface colours (red, orange, brown, yellow, green, blue, purple, white, grey and black), which were presented in two shapes (lines and dots) and three sizes. The surface colours were also named by an age-matched group of 20 subjects with normal colour vision. The performance of the clinical tests to predict the CVD subjects who made no colour naming errors and those who made errors is expressed in terms of the predictive value of a pass P((P)) and the predictive value of a fail P((F)). RESULTS: The P((P)) values of the tests were between 0.59 and 0.70 and P((F)) values were between 0.77 and 1.00. CONCLUSIONS: A 'mild' classification with the Richmond HRR test, especially if no more than two errors are made on the HRR diagnostic plates, identifies patients with abnormal colour vision who are able to name surface colour codes without error or only the occasional error. A pass of the Farnsworth D15 test identifies patients who will make no or few (up to 6%) errors with a 10 colour code, but who will be able to name the colours of a seven colour code that does not include orange, brown and purple. If protans are excluded, the predictive value for a pass P((P)) for the Farnsworth D15 is improved from 0.59 to 0.70. The anomaloscope is not an especially good predictor of those who can recognise surface colour codes. However, an anomaloscope range >35 units identifies those who have difficulty in recognising surface colour codes, as does a fail at the Farnsworth D15 test.     

Normal test scores in the Farnsworth-Munsell 100 hue test

One hundred and sixty persons aged from 10 to 69 years (106 women, 54 men) with healthy eyes were studied with the Farnsworth–Munsel1 100 hue (FM100) test. The mean of the results in the total scores and in the individual box scores in the right and left eye were calculated. The total score was also separately calculated in women and men. The test was administered under the illumination of Macbeth Easel lamp, 1000 lux, and the right eye was tested first. The results were calculated in six different age groups, 10–19 years, 20–29 years, etc. The mean of the total scores in the right eye varied from 7.44±2.46 (SD) to 10.07±2.03 in different age groups and in the left eye from 7.56±2.36 to 10.16±2.68. The scores changed significantly with the age: the correlation between the age and the test scores by linear regression gave significant results, in the right eye (R = 0.308, P = 0.0001), and in the left eye (R = 0.246, P = 0.0021). The present study with the normal error scores in the FM100 test and its individual boxes in persons aged 10–69 years gives clinicians working with colour vision defects a possibility to estimate the normality or abnormality of the results in their patients.     

Pass rates for the Farnsworth D15 colour vision test.

INTRODUCTION: The Farnsworth D15 test (D15) is used worldwide to select applicants for employment in occupations which require good colour vision. People with slight colour deficiency are intended to pass the D15 and people with significant (moderate/severe) colour deficiency to fail. METHODS: Pass rates were determined for 710 adult males with red-green colour deficiency using three different pass criteria in general use. RESULTS: Forty-six per cent of subjects were successful when the pass criterion was a circular results diagram (one single transformation of adjacent hues was accepted as a pass), 53% passed when one red-green isochromatic error was allowed and 60% passed when two red-green isochromatic errors were permitted. The pass rate for 200 dichromats was 1.5% on a circular diagram, 3% on one red-green error and 6% on two red-green errors. Protans made fewer errors than deutans and more protans than deutans were successful when either one or two red-green crossings were permitted as a pass. CONCLUSION: A circular results diagram is the preferred pass criterion. This criterion most nearly fulfils the aim of the test to fail all dichromats and people with significant protanomalous and deuteranomalous trichromatism. A circular diagram is also easy to interpret consistently. Re-examination is recommended if there are only one or two red-green isochromatic error lines across the results diagram. This gives individuals with borderline slight/moderate colour deficiency an opportunity to pass at the second attempt.     

Are ethnic differences in the F‐M 100 scores related to macular pigmentation?

Background: It is known that the macular pigment can significantly affect colour matching and other aspects of colour vision tests. The difference in macular pigmentation between Asians and Caucasians may lead to different colour discrimination. Methods: This study compared chromatic discrimination between Asians and Caucasians using the Farnsworth‐Munsell 100 Hue test. Fifty Asians who were ethnically Chinese and 50 Caucasians served as subjects, ranging in age from 30 to 59 years. Results: The partial blue‐yellow square root error score of the Asian subjects was signifi‐cantiy higher than diat of the Caucasian subjects (p = 0.022) and die difference appeared to increase with age. Discussion: There was a difference in die F‐M 100 scores between the two groups. The difference was confined in die blue‐yellow region, producing a tritan‐like bias for the Asian group in die test.     

Statistical demonstration of minor colour vision abnormalities

Analysis of the results from 94 male and 94 female young normal trichromats on the 100 hue test and the Nagel and Pickford-Nicolson anomaloscopes shows that colour deviant and/or colour weak subjects can be distinguished from the wholly normal bulk by considering the normality of certain test result distributions as well as by considering the combinations between test results considered abnormal. The stated minor abnormalities of colour vision are frequent and their types are those described by Pickford and by Lakowski (never' colour asthenopia). They are recognised by means of the anomaloscopes and not by means of the 100 hue test.     

Is screening for congenital colour vision deficiency in school students worthwhile? A review a

This review analyses the literature on screening for congenital colour vision deficiency in school students, which predominantly uses the Ishihara test. The review was framed with respect to the established Wilson and Jungner criteria for screening programs. These criteria relate to the characteristics of the condition concerned, the performance of the screening test, the existence of treatment options and the performance of screening programs. The literature reviewed suggests that congenital colour vision deficiency has not been shown to increase risk of road traffic crashes and is not a preclusion to driver licensing in most developed countries. The occurrence of congenital colour vision deficiency has been used to limit entry into certain occupations; however, the value of screening school students with regard to occupational preclusion is questionable. Stronger evidence exists indicating no association between congenital colour vision deficiency and level of educational achievement. Studies showing any association between congenital colour vision deficiency and other health and lifestyle impacts were rare. The most commonly used screening test (using Ishihara pseudoisochromatic plates) performs well with respect to detecting red‐green colour vision deficiencies. Finally, the only interventions we identified for congenital colour vision deficiency were management ones around the availability of specific tinted lenses and computer programs to aid colour perception in certain tasks. Given this picture, the weight of evidence appears to be in favour of not adopting (or discontinuing) routine colour vision screening programs for school students; however, it may be worthwhile for a career advisor to refer school students to an optometrist or ophthalmologist for colour vision screening, upon expression of interest in an occupation where normal colour vision is either particularly desirable or is a regulatory requirement.