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PubMed1999

Medical students and congenital colour vision deficiency: unnoticed problems and the case for screening.

The results are given of a questionnaire study to determine the range of difficulties that doctors notice in their work due to congenital colour vision deficiency (CCVD). The study is primarily qualitative. A questionnaire was sent to 40 self-selected doctors, 35 of whom were general practitioners (GPs). All were administered a number of colour vision tests to assess the type and severity of their deficiency. Many difficulties and some ways of overcoming them were reported. Those with a mild deficiency reported fewer difficulties and this relationship was significant. Twenty-three of the doctors also reported difficulties as medical students and their answers are given verbatim. The results are discussed in relation to other studies and data on colour vision. The reasons for and against screening medical students for this deficiency are considered and it is concluded that there is a strong case for screening.

Color Perception Tests↗

PubMed1984

Correlation of color vision deficits and observable changes in the optic disc in a population of ocular hypertensives.

Both glaucomatous cupping and the presence of acquired color vision deficits have been reported to be precursors to the onset of visual field defects in patients with suspected glaucoma. To examine the relationship between early glaucomatous cupping and acquired color vision anomalies, we performed anomaloscope (Pickford-Nicholson) and Farnsworth-Munsell 100-Hue color vision tests in 48 ocular hypertensive eyes with either clinical evidence of early glaucomatous cupping (group 1) or no evidence of glaucomatous cupping (group 2). All patients had normal visual fields, as determined by extensive static perimetry of the central visual field and kinetic perimetry of the peripheral visual field. Although the overall incidence of blue and blue-green color vision anomalies in the ocular hypertensives was comparable with that reported in previous studies, we found no clear association between early glaucomatous cupping and color vision anomalies. The relationship between these two precursors to visual field loss remains unclear.

Adult↗

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↗

PubMedDate not supplied

Illuminant and observer metamerism and the Hardy-Rand-Rittler color vision test editions.

A previous study identified a significant metamerism in the several editions of the Hardy-Rand-Rittller pseudoisochromatic plates (HRR) but did not proceed to quantify the consequences of that metamerism (Dain, 2004). Metamerism arises from two sources and is almost inevitable when a printed color vision test is reproduced in several editions. Metamerism has two consequences; these are illuminant/source-based changes in performance and changes in performance with observer (less well known) when assessing anomalous trichromats. This study addresses the effects of illuminant/source and observer metamerism on the fourth editions of HRR. Groups of colors intended to lie on a dichromat confusion line generally remain on a confusion line when the source id changed. The plates appear to be resistant to each form of metamerism, perhaps because the features of the spectral reflectance are similar for figure color and background gray. As a consequence, the clinician needs to be less concerned about using a non-recommended source than was previously believed.

Color Perception↗

PubMedDate not supplied

Novel form of a single X-linked visual pigment gene in a unique dichromatic color-vision defect.

In normal trichromats, the long- (L) and middle-wavelength-sensitive (M) pigment genes are arranged in a head-to-tandem array on the X chromosome. Two amino acids at positions 277 and 285, encoded by exon 5 of the L and M genes, respectively, are essential for the spectral difference between L and M pigments whose spectral peaks are at approximately 560 and 530 nm. Intragenic or intergenic unequal crossing-over commonly occurs between the highly homologous L and M genes, resulting in red-green color vision deficiencies. The dichromacy is usually associated with a single L gene for deuteranopia or a single 5' L-M 3' hybrid gene with M-gene exon 5 for protanopia. We clinically diagnosed a total of 88 male dichromats using a Nagel model I anomaloscope, which included one unclassified subject in addition to 31 protanopes and 56 deuteranopes. The objective of this study was to characterize the phenotype of the subject and to determine the genotype of his X-linked pigment genes. The subject accepted not only any red-green mixture but also an extended yellow-scale range at each matching point (i.e. 20 to 32 scale units at the green primary and 3.5 to 6 scale units at the red primary). The slopes of regression lines were in the range of -0.34 to -0.23, while the mean slopes for the protanopes and deuteranopes were -0.38 and -0.01, respectively. Spectral sensitivity tests showed that the subject's curve was shifted between the protanope and deuteranope curves. Molecular analysis revealed a novel form of a single pigment gene with a unique arrangement of exon 5 (Y277 from the L gene and A285 from the M gene). The predicted lambdamax (541 to 546 nm) of the unique pigment was closer to the M than to the L pigment. Our outcome suggests that intragenic unequal crossing-over may have occurred between amino acid positions 279 and 283.

Adult↗

PubMed1996

Colour contrast thresholds in congenital colour defectives.

The influence of congenital colour defects on a clinical computer test for equiluminous colour discrimination is studied. Differences in relative spectral sensitivity and changes in colour contrast discrimination are two distinct manifestations of the abnormal genes responsible for congenital red-green defects. The very simple and rapid method of the heterochromatic flicker brightness test acts like an anomaloscope and can be used to distinguish protan and deuteran defectives. The depth of the congenital colour defect can be quantified by the colour contrast threshold measured in equiluminous conditions along a single red-green axis identical for all types of red-green colour defectives. Colour contrast thresholds in tritan colour axes are not influenced by congenital red-green defects and therefore they are of extreme clinical interest to detect and quantify acquired colour defects, even in the presence of a previously unknown congenital red-green defect.

Color Perception Tests↗

PubMed1982

A method for quantitative scoring of the Farnsworth Panel D-15.

The Farnsworth Dichotomous test or Panel D-15 is used extensively for the evaluation of colour discrimination in congenital and acquired colour vision defects. This qualitative assessment of colour vision defect type and severity is based on the hue confusions which are represented diagrammatically on the Panel D-15 score sheet. This paper presents a new proposal for quantitatively scoring the Panel D-15 based on those hue confusions made by the subject. Such a quantitative score can be used to establish relationships with other visual functions or experimental conditions. The application of the scoring technique to clinical results is illustrated.

Color Perception Tests↗

PubMed2001

Towards a model to predict macular dichromats' naming errors: effects of CIE saturation and dichromatism type.

Thirty macular dichromat children (12 protanopes + 18 deuteranopes) and 29 controls, between 5 and 9 years old, participated in a monolexemic denomination task. Their clinical status was determined after a repeated application of a chromatic test set (Ishihara, CUCVT, and TIDA). The stimuli to be named were 12 tiles from the Color-Aid set belonging to the green, blue, and purple basic categories. Results showed that: (a) Dichromats made more naming errors when low saturation stimuli were used; (b) protanopes made more errors that deuteranopes; and (c) pseudoisochromatic lines predicted accurately the type of most frequent naming errors but they underestimated macular dichromats' functional capacity to name colors. Results are consistent with a model of macular dichromats' vision that hypothesizes a residual third type of cone in the periphery of the retina. Implications of this fact for everyday use of colors by macular dichromats' and for the validity of standard clinical diagnoses are discussed.

Child↗

PubMed1980

Results of colour vision tests in alcoholic and in mentally disordered subjects.

The responses at the Ishihara test, the Nagel anomaloscope, the standard Panel D--15 and the 100 hue test (with correction of the age effect) were recorded in 38 alcoholics in deprivation period (successively subdivided according to age, to abstinence duration and to liver condition) and in 32 subjects suffering from mental diseases (successively subdivided according to ethylic past, to age, to duration of the stay in the hospital and to activity). It is shown that alcoholism causes a diminution of the performance at the used colour vision tests and especially at the 100 hue test. The defect can be ascribed to psychical factors (chiefly in the cases of mental disease and in the younger people), but also to an acquired blue-yellow defectiveness of colour vision with a shift of the Rayleigh match to red (such a defectiveness can also be due to a liver damage and to some intoxications) and even to a Type II acquired red-green defectiveness of colour vision (possibly by tobacco or disulfiram intoxication). The defect due to alcohol itself soon disappears during desintoxication. The authors draw some practical conclusions.

Adult↗

PubMedDate not supplied

Anomalous trichromats' judgments of surface color in natural scenes under different daylights.

Deuteranomalous trichromacy, which affects medium-wavelength-sensitive cones, is more common than protanomalous trichromacy, which affects long-wavelength-sensitive cones. The aim of the present work was to test the extent to which these two kinds of anomalous trichromacy affect surface-color judgments in the natural world. Simulations of 18 natural scenes under different daylight illuminants were presented on a high-resolution color monitor to 7 deuteranomalous, 7 protanomalous, and 12 normal trichromatic observers, who had to discriminate between reflectance and illuminant changes in the images. Observers' ability to judge surface color was quantified by a standard color-constancy index. Deuteranomalous trichromats performed as well as normal trichromats, but protanomalous trichromats performed more poorly than both. The results are considered in relation to the spectral coverage of cones, rod intrusion, and the characterization of anomalous trichromacy by the Rayleigh match.

Adolescent↗

PubMed1997

Luminance contrast and colour contrast related errors in pseudoisochromatic plate identification.

PURPOSE: To determine whether differences in luminance contrast and colour contrast are factors in failing to identify American Optical pseudoisochromatic plates (AOPP). METHODS: We studied two groups of subjects. In 20 normal test subjects with no errors on the AOPP we used cross-polarising filters to darken and then gradually increase perceived luminance of the AOPP until these normal subjects correctly identified the plate. In a second group, to evaluate the relationship between a luminance contrast sensitivity score using Arden plates and AOPP identification, we tested 37 non-colour-deficient subjects who missed zero to five of the AOPP of low colour and luminance contrast (plates 9-12, 15). RESULTS: Using the cross-polarising filters, we found five plates that required more light to identify (plates 9-12, 15). In the second experiment, we found a significant relationship between the number missed of these five AOPP plates and a decrease in contrast sensitivity (r = 0.91, p < 0.001, Spearman correlation coefficient). CONCLUSION: Errors in AOPP colour plate detection may be due to loss of ability to perceive colour contrast and possibly luminance contrast.

Adult↗

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↗

PubMed1996

Foveal color and luminance sensitivity losses in glaucoma.

BACKGROUND AND OBJECTIVE: Losses in color vision sensitivity are noted in patients with glaucoma and these losses can occur before the onset of visual field defects in ocular hypertensive patients. The authors incorporate a technique that measures foveal luminance and isoluminant-color thresholds. PATIENTS AND METHODS: This study included 31 patients with glaucoma, 10 patients suspected of having glaucoma, and 67 control subjects. The testing conditions measured thresholds under identical spatial and temporal conditions. Individual differences in luminosity between colors were controlled by presenting 16 different ratios of the three phosphors on a color monitor. RESULTS: Relative to the control subjects, the patients with glaucoma showed a nonselective defect in both color and luminance sensitivity for red-green stimuli (P < .05), but a selective color defect for yellow-blue stimuli (P < .01). There were no statistically significant differences between patients suspected of having glaucoma and control subjects (P > 0.3). CONCLUSION: If the isoluminant-color stimuli are detected by foveal P-ganglion cells, then these results suggest that glaucoma leads to a generalized decrease in P-ganglion cell sensitivity that is more pronounced for cells with an input from cones sensitive to short wavelengths.

Adult↗

PubMed1990

Hue discrimination and S cone pathway sensitivity in early diabetic retinopathy.

Measures of hue discrimination and M (green) and S (blue) cone pathway sensitivities were compared in a group of 24 diabetics with either early background retinopathy or no retinopathy. The Farnsworth-Munsell 100-hue test was used to measure hue discrimination, and a two-color increment threshold technique was used to measure S and M cone pathway sensitivities. The results were compared to the level of diabetic retinopathy, to the degree of macular edema, and to the duration of the disease. No significant correlation was found between the Farnsworth-Munsell 100-hue error scores and the level of retinopathy; S cone pathway sensitivity loss, however, correlated significantly with both the level of retinopathy and the degree of macular edema. Our results indicate that measurements of S cone pathway sensitivity using an increment threshold technique provide a more sensitive method than hue discrimination for detecting color vision deficits in early diabetic retinopathy.

Adult↗

PubMed1981

Xenon arc and argon laser photocoagulation in the treatment of diabetic disc neovascularization. Part 2. Effect on colour vision.

Patients with long-standing diabetes develop acquired colour vision defects in parallel with retinal vascular changes. This may take the form of an overall loss of hue discrimination or a specific tritan (blue) defect. A battery of colour vision tests can be used to monitor the different features of diabetic retinopathy and to assess the effects of treatment. Diabetic disc new vessels form when approximately a quarter of the retina is ischaemic. The colour vision defect in these patients is usually severe and is frequently tritanopic. The effect of both argon laser and xenon arc panretinal photocoagulation is to increase the severity of the colour defect. All the eyes examined were tritanopic after treatment and did not recover during the 12-month follow-up period. The severity of this acquired colour vision defect can result in practical difficulties for the patient.

Adult↗

PubMed1981

Acquired color vision changes in glaucoma. Use of 100-hue test and Pickford anomaloscope as predictors of glaucomatous field change.

A five-year follow-up of eyes with elevated intraocular pressures, but without field defects, in which the color vision had been assessed by the 100-Hue test and an anomaloscope was carried out. Field defects developed in eight of 42 eyes with a low 100-Hue score, whereas field defects developed in ten of 13 eyes with a high abnormality in the 100-Hue test score. In the case of the anomaloscope (Pickford Nicholson) scores, field defects developed in four of five eyes with poor yellow-blue scores, whereas similar field defects developed in only nine of 40 years with a normal yellow-blue scores. With regard to blue-green scores, field defects developed in six of 11 eyes with a poor blue-green score, whereas field defects developed in only seven of 40 eyes with a normal blue-green score. These differences are statistically significant, and the probabilities of an abnormal color vision the results in subsequent field defects have been worked out. The red-green scores were not predictive.

Color Perception Tests↗

PubMed1997

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 35 mm 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.

Adult↗

PubMed1998

[Computer-based determination of red/green color vision defects].

A commonly used method of investigating colour vision, that is, the ability of the human visual system to discriminate colours, is based on the use of isochromatic colour plates, such as those used in the Ishihara test. The present paper describes a new computer-based method of determining red/green colour vision deficiencies. The method involves the presentation of Ishihara colour plates on a computer monitor. It has been verified experimentally that, despite the differences between the spectral emission of the computer screen and the daylight reflected by the Ishihara plates, the method is capable of distinguishing between subjects with from those without colour vision deficiencies. For screening purposes, the use of a reduced number of plates is suggested. This suggestion makes use of nine instead of 14 plates, and the criterion of two incorrectly recognized plates to determine a colour vision deficiency.

Adult↗