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PubMed2003

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 identifying 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.

Adolescent↗
PubMed2004

The handicap of abnormal colour vision.

All people with abnormal colour vision, except for a few mildly affected deuteranomals, report that they experience problems with colour in everyday life and at work. Contemporary society presents them with increasing problems because colour is now so widely used in printed materials and in computer displays. Equal opportunity law gives them protection against unfair discrimination in employment, so a decision to exclude a person from employment on the grounds of abnormal colour vision must now be well supported by good evidence and sound argument. This paper reviews the investigations that have contributed to understanding the nature and consequences of the problems they have. All those with abnormal colour vision are at a disadvantage with comparative colour tasks that involve precise matching of colours or discrimination of fine colour differences either because of their loss of colour discrimination or anomalous perception of metamers. The majority have problems when colour is used to code information, in man-made colour codes and in naturally occurring colour codes that signal ripeness of fruit, freshness of meat or illness. They can be denied the benefit of colour to mark out objects and organise complex visual displays. They may be unreliable when a colour name is used as an identifier. They are slower and less successful in search when colour is an attribute of the target object or is used to organise the visual display. Because those with the more severe forms of abnormal colour vision perceive a very limited gamut of colours, they are at a disadvantage in the pursuit and appreciation of those forms of art that use colour.

Color Vision Defects↗
PubMed2004

Clinical colour vision tests.

The structure and function of the available and significant clinical colour vision tests are reviewed in the light of the needs in the clinical examination of congenital and acquired colour vision deficiencies. The tests are grouped and described as pseudo-isochromatic plates, arrangement tests, matching tests and vocational tests. The colorimetric constructions of the test types are described and the efficiency of their performance and usefulness discussed. Recommendations are made for basic and extended test batteries, when examining of congenital and acquired colour vision deficiencies in the consulting room.

Color Perception Tests↗
PubMed2004

Visual search and the conspicuity of coloured targets for colour vision normal and colour vision deficient observers.

BACKGROUND: Colour is known to facilitate visual search although its role as a determinant of target conspicuity is not so clear. People with abnormal colour vision have problems recognising and differentiating colours but the extent to which they may be at a disadvantage in visual search when redundant colour is a target attribute has not been investigated previously. METHOD: Six colour normal and 29 colour deficient subjects (7 P, 6 D, 7 PA, 9 DA) were instructed to find a diamond-shaped target embedded in a background of 138 differently shaped distracters and to report its position as quickly as possible. The target was redundantly colour-coded red, yellow, green, blue or white and the distracters had the same colours in various combinations. The target was uniquely colour-coded in some presentations, partially redundant in others and in some presentations the target and distracters had the same colour. In experiment 1 the displays were presented for 20 seconds and search time was measured; in experiment 2 the exposure time was 500 ms and the proportion of targets located correctly was taken as a measure of the target's conspicuity. RESULTS: Unique colour coding reduced search times significantly and greatly enhanced conspicuity but had no benefit when some distracters had the same colour as the target. Observers with colour vision deficiency had longer search times and the coloured targets were less conspicuous to them compared with colour normal observers. However, unique colour coding assisted their search, especially when the targets were red, blue or white. CONCLUSIONS: Observers with colour vision deficiency are less efficient than colour normal observers at visual search when the target is marked out by colour and coloured targets are less conspicuous for them.

Adult↗
PubMed2004

The description of physical signs of illness in photographs by physicians with abnormal colour vision.

BACKGROUND: Physicians with congenital colour vision deficiency (CCVD) have reported difficulties recognising certain physical signs of illness, for example, jaundice, red rashes and pallor, and interpreting coloured charts, diagrams and slide projections. However, there has been little study of the effects of CCVD on the performance of medical practitioners. AIM: The aim of this study was to look for evidence of the effect of CCVD on the ability of physicians to recognise and describe physical signs of illness that have colour as either the main or an important feature. METHOD: Twenty-three general practitioners with CCVD were shown 11 colour photographs depicting colour signs of illness and were asked to describe the signs they saw and rate their confidence in making their descriptions. Their responses were compared to those of 23 age-matched general practitioners with normal colour vision. RESULT: General practitioners with CCVD compared to those with normal colour vision had less ability and confidence in detecting physical signs in the photographs and naming the colours. CONCLUSIONS: The results of this study support other evidence that physicians with CCVD have difficulties detecting some colour signs of illness and naming the colours. Because of the use of photographs the extent of the problem in clinical practice is unknown but medical practitioners with CCVD should be aware of the possibility of failing to detect or correctly assess physical signs that are characterised by colour.

Color Vision Defects↗
PubMed2005

The effect of abnormal colour vision on the ability to identify and outline coloured clinical signs and to count stained bacilli in sputum.

AIM: To determine if medical practitioners with congenital colour vision deficiencies (CCVD) are less able to identify and delineate the extent of coloured abnormal signs than those with normal colour vision. METHOD: Twenty-two medical practitioners with CCVD and 17 with normal colour vision, matched for age and gender, were shown 10 photographs. They were asked to identify and outline the extent of the clinical sign in eight that were of vomit or stool (six of these showing fresh blood), one of a skin rash and for one to mark the position of bacilli in sputum stained by the Ziehl-Neelsen method. RESULTS: There were statistically significant differences between the CCVD practitioners and those with normal colour vision in their ability to outline abnormalities in five of the six photographs that showed fresh blood, in the photograph of a rash and in marking the position of bacilli in the photograph of a stained slide. CONCLUSION: Medical practitioners with CCVD are handicapped in their evaluation of the presence and extent of coloured clinical signs. Medical schools should ensure that students with CCVD are aware of their deficiency and know its severity, so they can take special care in clinical practice.

Bacillus↗
PubMed2005

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).

Adult↗
PubMed2005

Diagnosing protan heterozygosity using the Medmont C-100 colour vision test.

BACKGROUND: A surprisingly high 15 per cent of women in Caucasian societies are carriers of the genes for abnormal colour vision but there is no clinical method to identify them. It has long been known that heterozygotes for the protan colour vision deficiencies can demonstrate a reduced luminous sensitivity to red light. This is known as Schmidt's sign, which is thought to arise from mosaicism (Lyonisation). The Medmont C-100 colour vision test measures relative spectral sensitivity using flicker photometry to differentiate protans and deutans. It should be able to diagnose Schmidt's sign. METHOD: We tested six known protan heterozygotes (four whose sons have a protan colour vision deficiency and two whose fathers are protan) with the Medmont C-100 test. RESULTS: All six heterozygotes made average settings of -1.75 or more negative at the Medmont C-100 test, settings which are at or beyond the boundary of the distribution of settings made by observers with normal colour vision. There have been two previous cases reported in the literature of protan heterozygotes, who made protan settings on the Medmont C-100 or its predecessor test, the OSCAR. We also tested six daughters of the known heterozygotes, 50 per cent of whom are likely to be heterozygotes. Four of the six (66 per cent) made protan settings on the Medmont C-100. The other two made normal 0.0 settings. CONCLUSION: We conclude that the Medmont C-100 can be used clinically to diagnose carriers of protan colour vision deficiency.

Color Perception Tests↗
PubMed2006

Search for coloured objects in natural surroundings by people with abnormal colour vision.

BACKGROUND: People with abnormal colour vision often report difficulty seeing coloured berries and flowers in foliage, which suggests they will have a diminished capacity for visual search when target objects are marked out by colour. There is very little experimental evidence of the effect of abnormal colour vision on visual search and none relating to search for objects in natural foliage. METHOD: We showed 79 subjects with abnormal colour vision (seven protanopes, 10 deuteranopes, 16 protanomals and 46 deuteranomals) and 20 subjects with normal colour vision photographs of natural scenes and asked them to locate clumps of red berries, to trace the length of a red string on grass and to name the season depicted in a photograph taken in the Autumn and the same scene photographed in the Summer. Colour vision was assessed using the Ishihara, the Medmont C100, the Farnsworth D15, the Richmond HRR and the Nagel anomaloscope. RESULTS: All the subjects with abnormal colour vision located fewer clumps of red berries than those with normal colour vision. The subjects who failed the Farnsworth D15 performed significantly worse than those who passed but the distribution of scores in the two groups overlaps. The majority of subjects with abnormal colour vision could not trace the full length of the string: only 38 per cent of anomalous trichromats who passed the Farnsworth D15 test and three per cent of those who failed it were able to trace the full length of the string. Fifty-five per cent of those classed as having a mild deficiency by the HRR test could trace the whole string. Most dichromats were unable to identify the Autumn season and those who did may have been assisted by guessing. Most (94 per cent) of those who passed the Farnsworth D15 test and all those classified as having a 'mild' deficiency by the HRR test could identify the season. CONCLUSIONS: All people with abnormal colour vision, even those with a very mild deficiency, have some degree of impairment of their ability to see coloured objects in natural surroundings. A pass at the Farnsworth D15 test or a 'mild' classification with the Richmond HRR test identifies those likely to have the least problems with visual search and identification tasks. The results have practical implications for the selection of personnel in occupations that involve visual search in natural terrain.

Adolescent↗
PubMedDate not supplied

Detection of cone dysfunction induced by digoxin in dogs by multicolor electroretinography.

It is difficult to detect discrete cone function with the present conventional electroretinography (ERG) examination. In this study, we developed contact electrodes with a built-in color (red (644 nm), green (525 nm), or blue (470 nm)) light source (color LED-electrode), and evaluated an experimental model of digoxin in the dog. First, 17 normal Beagle dogs were used to determine which electrode works well for color ERG measurement on dogs. Then, color ERG was performed on seven normal Beagle dogs at various points during a 14-day period of digoxin administration. A single daily dose of 0.0125 mg/kg/day, which is within the recommended oral maintenance dosage range for dogs, was administered orally for 2 weeks. Ophthalmic examination, measurement of plasma concentration of digoxin, and color ERG examination were performed. On first examination, amplitudes of all responses were significantly (P < 0.01) lower with the red, than with the blue and green electrodes during ERG recording. In ERG using the red electrode, the standard deviation was large. According to these preliminary results, the red electrode was not used in the experimental dog model with digoxin. In the digoxin administrated animals, no significant change was observed in the ophthalmic examination findings. The digoxin level increased steadily throughout the dosing period but was always within the therapeutic range for dogs. In rod ERG, no abnormalities were detected with any electrode. In standard combined ERG, decreased amplitude of the a-wave was detected with every electrode. In single flash cone ERG, prolongation of implicit time was detected by color ERG with the blue and green electrodes. In 30-Hz flicker ERG, decreased amplitude was detected only by color ERG with the blue electrode. The decreased amplitude and prolonged implicit time recovered after termination of digoxin administration. Cone dysfunction induced by digoxin in the dog was revealed by multicolor ERG using blue and green LED-electrodes. Multi-color ERG was useful for detecting cone type-specific dysfunction in the dog.

Administration, Oral↗