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PubMed2001

Color discrimination in heterozygous deutan carriers.

PURPOSE: The color discrimination abilities of heterozygous deutan female carriers were measured using color mixture thresholds and compared with those of suspected nonheterozygous normal subjects. METHODS: Eight test subjects and 26 control subjects were run on a computer-controlled color test (color mixture thresholds) that presented 1 degree diameter spots on a color television monitor for 1/60 of a second. A QUEST procedure was used to determine visual thresholds for spots varying in brightness and/or color. Individual data points were graphed on an X/Y plot and fitted with an ellipse. The major and minor diameters of the ellipse represent the color and brightness thresholds, respectively. RESULTS: The mean axis angle of the ellipse for the heterozygous carriers did not differ from that for the controls (15.75 degrees vs. 14.93 degrees, p = 0.428, Mann-Whitney test). The carriers did show, however, a larger mean major axis length (68.79 vs. 46.78, p = 0.0218, Mann-Whitney test). Additionally, the length-to-width ratios for the carriers were higher than the controls (9.34 vs. 6.80, p = 0.0403, Mann-Whitney test). CONCLUSIONS: Deutan-carriers do show reduced color purity discrimination as measured using color mixture thresholds compared with nonheterozygous, color vision normals.

Adolescent↗
PubMed1993

Visual abnormalities associated with high-energy microwave exposure.

A 44-year-old man was accidentally exposed to high-energy microwave irradiation. After resolution of facial erythema and iritis, he noted a foreign body sensation and blurring of vision. Ophthalmoscopic examination showed bilateral, small hard drusen. Ancillary tests were consistent with abnormal cone function. Electroretinogram testing revealed a marked decrease in the flicker electroretinogram. Results of D15 and Farnsworth Munsel Hue 100 color tests were abnormal. Two years later, the patient's visual acuity was stable at 20/25 in both eyes; however, results of flicker electroretinogram test remain markedly decreased.

Adult↗
PubMed1998

Legal blindness and employment in patients with juvenile-onset macular dystrophies or achromatopsia.

PURPOSE: The purpose of this study was to gain information about the employment status of legally blind patients. METHODS: Fifty-two patients with one of four juvenile-onset macular dystrophies or achromatopsia responded to questions about their employment histories and their psychological well-being. Results from the questionnaire were analyzed using z-tests for differences in proportions or t-tests for differences in means. RESULTS: Forty-eight percent of the patients reported that they were employed and 52% that they were not employed. The subgroup that was not employed had a significantly higher proportion of women than men, whereas the employed group had approximately equivalent proportions of men and women. The employed subgroup reported that their success at work was due to social support. This subgroup had significantly higher household incomes, was significantly less likely to collect disability-income benefits, had significantly higher educational levels, had significantly higher positive affect, and had significantly lower negative affect than the subgroup that was not employed. A logistic regression analysis indicated that education was the primary predictor of employment. CONCLUSION: Analysis supports the conclusion that it is beneficial for legally blind individuals to obtain an optimal level of education and receive suitable social support to facilitate their successful employment.

Adolescent↗
PubMed2001

Intervention study on acquired color vision deficiencies in styrene-exposed workers.

The main aim of the study was to examine the possible effects of occupational exposure to styrene on color vision function and the course after reduction of exposure. Color vision function was examined in 22 styrene-exposed laminators and 11 control subjects at a boat manufacturing plant. The Lanthony D-15 desaturated panel was used to test acquired dyschromatopsia. In all, six examinations were performed: Monday morning and Thursday afternoon of the same week, before and immediately after a vacation of 4 weeks (altogether, phase 1), and approximately 10 months later (phase 2), after the exposure level of styrene had been reduced. Styrene uptake was objectified by biological monitoring measuring the metabolites mandelic acid and phenylglyoxcylic acid in urine samples taken on Thursday afternoon. In both Thursday examinations, styrene-exposed workers had higher color confusion index (CCI) values compared with controls, which indicated quantitative color vision loss. After an exposure-free period of 4 weeks, a significant decrease of CCI values to normal range was found in laminators. Reexamination 10 months later showed also lower CCI values in exposed workers, indicating a dose-effect relationship. Abnormal CCI values occurred primarily in subjects with an excretion of approximately 500 to 600 mg mandelic acid plus phenylglyoxcylic acid per gram creatinine or more. We concluded that styrene-induced color vision dysfunction is reversible after an exposure-free interval of 4 weeks. The current Biological Tolerance Value of 600 mg mandelic acid plus phenylglyoxcylic acid per gram creatinine, as used in Germany, protects styrene-exposed workers from this subclinical effect.

Adult↗
PubMed2006

Frequency of colour vision deficiencies in melanoma patients: results of a prospective comparative screening study with the Farnsworth panel D 15 test including 300 melanoma patients and 100 healthy controls.

Patients with melanoma may experience a variety of different vision symptoms, in part associated with melanoma-associated retinopathy. For several melanoma patients with or without melanoma-associated retinopathy, colour vision deficiencies, especially involving the tritan system, have been reported. The frequency of colour vision deficiencies in a larger cohort of melanoma patients has not yet been investigated. The aim of this study was to investigate the frequency of colour vision deficiencies in melanoma patients subject to stage of disease, prognostic factors such as tumour thickness or Clark level, S100-beta and predisposing diseases that may have an impact on colour vision (hypertension, diabetes mellitus, glaucoma or cataract). Three hundred melanoma patients in different tumour stages and 100 healthy age-matched and sex-matched controls were examined with the saturated Farnsworth panel D 15 test. Seventy out of 300 (23.3%) melanoma patients and 12/100 (12%) controls showed pathologic results in colour testing. This discrepancy was significant (P < 0.016; odds ratio = 2.23, 95% confidence interval 1.15-4.32). Increasing age was identified as a highly significant (P = 0.0005) risk factor for blue vision deficiency. Adjusting for the age and predisposing diseases, we could show that melanoma was associated with the risk of blue vision deficiency. The frequency of blue vision deficiency in 52/260 melanoma patients without predisposing diseases (20%) compared with 4/78 controls without predisposing diseases (5.1%) differed significantly (odds ratio 4.441; confidence interval 1.54-12.62; P < 0.004). In 260 melanoma patients without predisposing diseases, blue vision deficiency, as graded on a 6-point scale, showed a weak positive correlation (Spearman) with tumour stage (r = 0.147; P < 0.01), tumour thickness (r = 0.10; P = 0.0035), Clark level (r = 0.12; P = 0.04) and a weak negative correlation with time since initial diagnosis (r = -0.11; P = 0.0455). Blue vision deficiency is associated with melanoma, but is only weakly related to stage of disease. Although we saw a positive correlation with well-known prognostic markers, such as tumour thickness and Clark level, blue vision deficiency as assessed by the Farnsworth panel D 15 test in general is inappropriate as a marker of tumour progression. For the use of blue vision deficiency in melanoma patients without predisposing diseases, a diligent test performance and interpretation is very important.

Adult↗
PubMed2006

Categorical color naming of surface color codes by people with abnormal color vision.

PURPOSE: Past investigations of the ability of people with color vision deficiency (CVD) to name the colors of surface colors have been occupation-specific. This study was undertaken as a more generalized investigation to explore particularly the effects of stimulus size and shape. METHODS: One hundred CVD observers and 20 color vision normal (CVN) subjects named the colors of two sets of surface colors, each set presenting the same 10 colors (red, orange, brown, yellow, green, blue, purple, white, gray, black). One set presented dot stimuli in three sizes (2.4 degrees , 1.0 degrees , 0.27 degrees ) and the other line stimuli with three widths (0.50 degrees , 0.27 degrees , 0.14 degrees ). Color vision was diagnosed using the Ishihara test, the Farnsworth D15 test, the Medmont C100, and the Nagel anomaloscope. RESULTS: All CVN subjects and 37% of CVD subjects made no errors. Type of CVD and stimulus size were significant factors for probability of error and the effect of stimulus size is best described by 1/area. There were significant interactions between CVD type and 1/area and between shape and 1/area. Deuteranomals who passed the Farnsworth D15 test made significantly fewer errors than all other CVD types and 70% made no errors. Their common errors were to confuse red, orange, and brown. Protanomals who passed the Farnsworth D15 test made fewer errors than dichromats. CONCLUSIONS: Mild deuteranomals will make very few errors with a seven-color code that omits orange, brown, and purple and will make very few errors (approximately 0.3%) with a 10-color code when the stimuli are reasonably large (area >20 mm).

Adolescent↗
PubMed2006

Evaluation of cerebral dyschromatopsia using color afterimage.

Cerebral dyschromatopsia is traditionally evaluated by color discrimination tests such as the Farnsworth-Maunsell 100 Hue Test. These tests are also used to evaluate color-perception deficits caused by eye disease, and they do not tell us whether color perception is impaired in the eye or in the brain. Here, we used color afterimage to isolate color-perception deficits in the brain from those in the eyes, in a patient with cerebral dyschromatopsia. The results showed that the patient perceived color afterimage of yellow and blue with abnormal duration and chromaticity. On the other hand, the patient performed normally on the Farnsworth-Maunsell 100 Hue Test. We conclude that the color afterimage test would be useful to evaluate color perception in the brain.

Color Perception↗
PubMed1984

Variations of colour vision in a New World primate can be explained by polymorphism of retinal photopigments.

The squirrel monkey (Saimiri sciureus) exhibits a polymorphism of colour vision: some animals are dichromatic, some trichromatic, and within each of these classes there are subtypes that resemble the protan and deutan variants of human colour vision. For each of ten individual monkeys we have obtained (i) behavioural measurements of colour vision and (ii) microspectrophotometric measurements of retinal photopigments. The behavioural tests, carried out in Santa Barbara, included wavelength discrimination, Rayleigh matches, and increment sensitivity at 540 and 640 nm. The microspectrophotometric measurements were made in London, using samples of fresh retinal tissue and a modified Liebman microspectrophotometer: the absorbance spectra for single retinal cells were obtained by passing a monochromatic measuring beam through the outer segments of individual rods and cones. The two types of data, behavioural and microspectrophotometric, were obtained independently and were handed to a third party before being interchanged between experimenters. From all ten animals, a rod pigment was recorded with lambda max (wavelength of peak absorbance) close to 500 nm. In several animals, receptors were found that contained a short-wave pigment (mean lambda max = 433.5 nm): these violet-sensitive receptors were rare, as in man and other primate species. In the middle- to long-wave part of the spectrum, there appear to be at least three possible Saimiri photopigments (with lambda max values at about 537,550 and 565 nm) and individual animals draw either one or two pigments from this set, giving dichromatic or trichromatic colour vision. Thus, those animals that behaviourally resembled human protanopes exhibited only one pigment in the red-green range, with lambda max = 537 nm; other behaviourally dichromatic animals had single pigments lying at longer wavelengths and these were the animals that behaviourally had higher sensitivity to long wavelengths. Four of the monkeys were behaviourally judged to be trichromatic. None of the latter animals exhibited the two widely separated pigments (close to 535 and 567 nm) that are found in the middle- and long-wave cones of macaque monkeys.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Dichromats detect colour-camouflaged objects that are not detected by trichromats.

To explain the surprisingly high frequency of congenital red-green colour blindness, the suggestion has been made that dichromats might be at an advantage in breaking certain kinds of colour camouflage. We have compared the performance of dichromats and normal observers in a task in which texture is camouflaged by colour. The texture elements in a target area differed in either orientation or size from the background elements. In one condition, the texture elements were all of the same colour; in the camouflage condition they were randomly coloured red or green. For trichromats, it proved to be more difficult to detect the target region in the camouflage condition, even though colour was completely irrelevant to the task. Dichromats (n = 7) did not show this effect, and indeed performed better than trichromats in the camouflage condition. We conclude that colour can interfere with segregation based upon texture, and that dichromats are less susceptible to such interference.

Color Perception↗
PubMed1995

Colour identification and colour constancy are impaired in a patient with incomplete achromatopsia associated with prestriate cortical lesions.

We have examined visual functions, including colour vision, in a patient with bilateral cortical lesions involving mainly the fusiform and lingual gyri, areas known to be involved in the central processing of chromatic stimuli. The patient has near normal (6/9) acuity, and his responses to tests of binocular function and spatial vision are normal, as are his discrimination of changes in target speed and surface lightness. He does, however, exhibit minor losses in the upper visual field, mild prosopagnosia and topographical agnosia, all conditions commonly associated with cerebral achromatopsia. Colour matches and spectral response data establish that his cone photoreceptors have normal spectral characteristics and his spectral sensitivity measured against a white background reveals normal postreceptoral chromatic function. The patient's colour discrimination for differences in wavelength, hue or saturation is, however, impaired and his colour naming is significantly disturbed, particularly for blues and greens. We have determined the areas of the chromaticity chart that correspond to his naming categories for surface colours, and show that changes in illuminant cause him to alter the names of surface colours in a manner consistent with the changes in their chromaticities. Other subjects with normal or congenital red-green deficient colour vision make many fewer name changes under changes in illuminant. We conclude that the patient's colour constancy is impaired as a consequence of abnormal central processing of colour vision.

Cerebral Infarction↗
PubMed1999

The clinical and functional measurement of cortical (in)activity in the visual brain, with special reference to the two subdivisions (V4 and V4 alpha) of the human colour centre.

We argue below that, at least in studying the visual brain, the old and simple methods of detailed clinical assessment and perimetric measurement still yield important insights into the organization of the visual brain as a whole, as well as the organization of the individual areas within it. To demonstrate our point, we rely especially on the motion and colour systems, emphasizing in particular how clinical observations predicted an important feature of the organization of the colour centre in the human brain. With the use of data from functional magnetic resonance imaging analysed by statistical parametric mapping and independent component analysis, we show that the colour centre is composed of two subdivisions, V4 and V4 alpha the two together constituting the V4 complex of the human brain. These two subdivisions are intimately linked anatomically and act cooperatively. The new evidence about the architecture of the colour centre might help to explain why the syndrome, cerebral achromatopsia, produced by lesions in it is so variable.

Carbon Monoxide Poisoning↗