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PubMedDate not supplied

An adaptation of the Cambridge Colour Test for use with animals.

Recently, molecular biological techniques have presented new opportunities for addressing questions concerning the neural mechanisms involved in color coding, thereby rousing renewed interest in animal color vision testing. We have modified a computer-based assessment tool, the Cambridge Colour Test, to make it suitable for use with animals. Here, the validity and reliability of the testing method were evaluated using squirrel monkeys. Because the chromatic stimuli and the achromatic backgrounds of the test consist of dots that vary in lightness, the stimulus parameters can be adjusted so that animals are not able to use luminance differences to make correct discriminations. Thus, in contrast to methods used previously, this test does not require that time be spent equating the luminance of each chromatic stimulus examined. Furthermore, the computer video-display based design of the testing apparatus can be easily replicated and adapted for use with many species in a variety of settings. In the present experiments, the squirrel monkeys' behavioral results agreed with the predictions for their color vision based on genetic analysis and electroretinography (ERG) spectral sensitivity data. Repeated measurements were highly consistent. Thus, an adaptation of the Cambridge Colour Test provides a valid and reliable method for testing color vision in animals.

Animals↗
PubMedDate not supplied

Color space distortions in patients with type 2 diabetes mellitus.

Color vision impairment was examined in patients with type 2 diabetes mellitus (DM2) without retinopathy. We assessed the type and degree of distortions of individual color spaces. DM2 patients (n = 32), and age-matched controls (n = 20) were tested using the Farnsworth D-15 and the Lanthony D-15d tests. In addition, subsets of caps from both tests were employed in a triadic procedure (Bimler & Kirkland, 2004). Matrices of inter-cap subjective dissimilarities were estimated from each subject's "odd-one-out" choices, and processed using non-metric multidimensional scaling. Two-dimensional color spaces, individual and group (DM2 patients; controls), were reconstructed, with the axes interpreted as the R/G and B/Y perceptual opponent systems. Compared to controls, patient results were not significant for the D-15 and D-15d. In contrast, in the triadic procedure the residual distances were significantly different compared to controls: right eye, P = 0.021, and left eye, P = 0.022. Color space configurations for the DM2 patients were compressed along the B/Y and R/G dimensions. The present findings agree with earlier studies demonstrating diffuse losses in early stages of DM2. The proposed method of testing uses color spaces to represent discrimination and provides more differentiated quantitative diagnosis, which may be interpreted as the perceptual color system affected. In addition, it enables the detection of very mild color vision impairment that is not captured by the D-15d test. Along with fundoscopy, individual color spaces may serve for monitoring early functional changes and thereby to support a treatment strategy.

Adult↗
PubMedDate not supplied

Color naming and categorization in inherited color vision deficiencies.

Dichromatic subjects can name colors accurately, even though they cannot discriminate among red-green hues (Jameson & Hurvich, 1978). This result is attributed to a normative language system that dichromatic observers developed by learning subtle visual cues to compensate for their impoverished color system. The present study used multidimensional scaling techniques to compare color categorization spaces of color-vision deficient (CVD) subjects to those of normal trichromat (NT) subjects, and consensus analysis estimated the normative effect of language on categorization. Subjects sorted 140 Munsell color samples in three different ways: a free sorting task (unlimited number of categories), a constrained sorting task (number of categories limited to eight), and a constrained naming task (limited to eight basic color terms). CVD color categories were comparable to those of NT subjects. For both CVD and NT subjects, a common color categorization space derived from the three tasks was well described by a three-dimensional model, with the first two dimensions corresponding to reddish-greenish and yellowish-bluish axes. However, the third axis, which was associated with an achromatic dimension in NTs, was not identified in the CVD model. Individual differences multidimensional scaling failed to reveal group differences in the sorting tasks. In contrast, the personal color naming spaces of CVD subjects exhibited a relative compression of the yellowish-bluish dimension that is inconsistent with the typical deutan-type color spaces derived from more direct measures of perceptual color judgments. As expected, the highest consensus among CVDs (77%) and NTs (82%) occurred in the naming task. The categorization behaviors studied in this experiment seemed to rely more on learning factors, and may reveal little about CVD perceptual representation of colors.

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↗
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↗
PubMed2003

Detecting color vision in a malingerer.

A patient describing himself as totally color blind was ordered by the judicial system to have his color vision investigated in order to establish his suitability for military service. Basic clinical (Farnsworth Panel D-15, Moreland and Rayleigh anomaloscope equations), electroretinographic (ERG) and psychophysical techniques (spectral sensitivities) were applied to determine the extent of his color discrimination performance and cone function. These standard procedures were complemented by a test for cone interaction (transient tritanopia) and by newly developed cone-isolating flicker large-field ERG recordings. The patient's data consistently indicate the function as well as the functional interaction of the middle-wavelength-sensitive (M-) and the short-wavelength-sensitive (S-) cones. But the function of the long-wavelength-sensitive (L-) cones was completely absent. Hence the patient was correctly demonstrated to be a protanope. This study establishes that standard classical procedures, in combination with newly developed and easy to apply psychophysical and ERG ones, which can be reliably used to assess true color discrimination performance, in difficult cases of malingering.

Adult↗
PubMed2003

ERGs, cone-isolating VEPs and analytical techniques in children with cone dysfunction syndromes.

Photoreceptor and post-receptoral function in children with congenital and acquired cone disorders was measured by full-field electroretinogram (ERG) and transient visual evoked potentials (VEPs). Subjects were five rod monochromats (RM), five with cone dystrophy (CD), and 30 controls. Patients were diagnosed by clinical findings, ERGs, and standard color vision tests. VEP stimuli were check reversals and color grating onsets that stimulated each photoreceptor type (L-, M-, or S-cones) or post-receptoral pathways (L-M, white/black). VEP signal-to-noise ratios (S/N) were calculated by Fourier analysis of VEP epochs. All RM patients showed extinguished cone ERGs. A near normal S-cone VEP was recorded from a blue-cone rod monochromat without any signal from the L- or M-cone stimuli. Two other RM patients were classified as incomplete RM based on a low-level VEP signal from either L- or M-cone stimuli. CD patients had mildly to severely reduced ERGs and VEPs were abnormal to all cone-isolating stimuli. The VEP S/N ratio was not significantly correlated with the amount of rod contrast in the color stimuli. Color VEPs provide an objective assessment of macular cone function in children with cone dysfunction syndromes that is more sensitive to residual central cone function than standard full-field ERGs. VEP techniques may be useful in the early detection of cone loss in children, especially in children who do not tolerate ERG testing.

Adolescent↗
PubMed2003

[Genetic causes of retinal degeneration].

Premature death of rod and cone photoreceptor cells in the human retina leads to severe visual handicaps in affected patients. The two most important groups of retinal dystrophies, macular degeneration and retinitis pigmentosa, differ in primary symptoms and disease progression. Macular degeneration starts in the central retina and progresses towards the periphery. In RP, photoreceptor cell death starts in the periphery and then proceeds to the central part of the retina. Molecular studies have revealed important new findings during the last decade. There are two important results to be emphasized: 1. The very same clinical symptoms can result from mutations in different genes. RP is a prominent example for this phenomenon. 2. Mutations in the same gene can result in different phenotypes. The correlation between genotype and phenotype is not essentially straight forward. This may indicate that other factors can influence the phenotypic consequences of mutations. Different X-linked retinal dystrophies represent excellent examples for these findings.

Adult↗
PubMed2002

Progress of visual dysfunction in Parkinson's disease.

Studies on progression of Parkinson's disease (PD) mainly focus on the nigrostriatal dopaminergic decline, but not on the visual system. We determined progression of (i) disturbed color vision, assessed with the Farnsworth-Munsell 100 Hue test (FMT) and (ii) intensity of PD in 18 patients. Significant differences occurred between (i) initial FMT error scores and follow-up results 3 years later (P=0.002) and analogously (ii) scored intensity of PD (P=0.002). A relation between computed differences of FMT error scores and rated activities of daily living appeared. Deterioration of color vision progresses in PD.

Color Perception↗
PubMed1998

Retinal function in Swedish ophthalmologists using argon lasers as reflected in colour contrast sensitivity. Normal thresholds in the great majority of the cases.

PURPOSE: To map the colour contrast sensitivity (CCS) and possible elevations of colour contrast thresholds in Swedish ophthalmologists operating argon lasers. MATERIAL AND METHODS: CCS was measured by a computer and colour monitor system developed by Arden and co-workers. CCS of 58 Swedish ophthalmologists, all users of argon laser, was compared to 26 age-matched controls. The ophthalmologists provided information on their professional use of lasers, whether the laser was equipped with a blue-absorbing filter, and the length of time spent in retinal surgery. RESULTS: There was no significant difference in colour vision comparing laser-users to controls (p>0.2). However, eight subjects showed elevated tritan thresholds (>1 SD above mean), in three of the cases an elevation >2 SD above mean. All these colleagues had an extensive exposure to blue-green laser and/ or a long time spent operating. Compared to others, they had performed more laser sessions prior to the lasers being equipped with protecting filters (p<0.01). CONCLUSION: Normal thresholds were found in a majority of the cases and no permanent impairment of retinal function was observed among these ophthalmologists. However, the laser-users with the greatest number of sessions seemed to show a certain decrease in retinal function as reflected in tritan thresholds.

Adult↗
PubMed2000

Quantitative anomaloscopy and optical coherence tomography scanning in central serous chorioretinopathy.

BACKGROUND: Dyschromatopsia is a prominent sign in a variety of central retinal diseases, such as central serous chorioretinopathy (CSC). The changes in colour vision may be due to either optical or neuronal factors in the diseased retina. The relative contribution from the two causes is unknown, but may be elucidated by obtaining knowledge of the anatomical derangement in the diseased retina in CSC. METHODS: Twenty-six normal persons had their colour vision tested using the Tomey anomaloscope. The calculation of setting range (SR) and central mean point (CMP) for Rayleigh match and Moreland match was optimized, and normal ranges for these values were defined. Subsequently 24 patients with CSC were examined by anomaloscopy and optical coherence tomography scanning, and the measures of colour vision were related to the anatomical changes observed on the scans. RESULTS: The algorithm for calculating SR and CMP which is integrated into the Tomey anomaloscope could be considerably improved to increase sensitivity and reproducibility of these measures. Fifteen patients had abnormal colour vision. Nine patients had pseudo-protanomaly, seven patients had pseudo-tritanomaly, and three patients had abnormalities in both matches. There was no relation between these colour vision abnormalities and the anatomical derangement as seen by OCT in the diseased central retina. CONCLUSION: The findings argue against the notion that the density of retinal cell nuclei, the orientation of photoreceptors, or the size of the central serous detachment are related to the colour vision abnormalities in CSC. The question of whether these abnormalities are due to optical or neuronal factors remains open.

Adult↗
PubMed1981

Premature cognitive commitment.

Two experiments examined the effect that the conditions of initial exposure to information have on the "mindless" processing of that information and its subsequent use. It was hypothesized that the context of initial exposure to information limits its subsequent use. Information initially perceived as irrelevant may be uncritically accepted. If that information later becomes relevant, persons become victims of their premature cognitive commitments. In the first experiment, all subjects received information about perceptual deficits while the perceived relevance of that information was manipulated. On assessment tests, all subjects "found" they had this deficit. On follow-up perceptual tasks, the group initially informed that the deficit was seemingly irrelevant showed severe performance decrements relative to other groups. The second experiment used a similar procedure for a perceptual skill rather than a deficit. Here, subjects initially exposed to "irrelevant" information performed more productively than subjects initially exposed to "relevant" information. These results indicate that conditions surrounding initial exposure to information limit its subsequent use. The implications of these data for social, psychological, and physical symptoms are discussed.

Adaptation, Psychological↗
PubMed1999

Trichromatic color vision with only two spectrally distinct photopigments.

Protanomaly is a common, X-linked abnormality of color vision. Like people with normal color vision, protanomalous observers are trichromatic, but their ability to discriminate colors in the red-green part of the spectrum is reduced because the photopigments that mediate discrimination in this range are abnormally similar. Whereas normal subjects have pigments whose wavelengths of peak sensitivity differ by about 30 nm, the peak wavelengths for protanomalous observers are thought to differ by only a few nanometers. We found, however, that although this difference occurred in some protanomalous subjects, others had pigments whose peak wavelengths were identical. Genetic and psychophysical results from the latter class indicated that limited red-green discrimination can be achieved with pigments that have the same peak wavelength sensitivity and that differ only in optical density. A single amino acid substitution was correlated with trichromacy in these subjects, suggesting that differences in pigment sequence may regulate the optical density of the cone.

Amino Acid Substitution↗