Specificity of the chromatic noise influence on the luminance contrast discrimination to the color vision phenotype.

Many studies have examined how color and luminance information are processed in the visual system. It has been observed that chromatic noise masked luminance discrimination in trichromats and that luminance thresholds increased as a function of noise saturation. Here, we aimed to compare chromatic noise inhibition on the luminance thresholds of trichromats and subjects with severe deutan or protan losses. Twenty-two age-matched subjects were evaluated, 12 trichromats and 10 with congenital color vision impairment: 5 protanopes/protanomalous, and 5 deuteranopes/deuteranomalous. We used a mosaic of circles containing chromatic noise consisting of 8 chromaticities around protan, deutan, and tritan confusion lines. A subset of the circles differed in the remaining circles by the luminance arising from a C-shaped central target. All the participants were tested in 4 chromatic noise saturation conditions (0.04, 0.02, 0.01, 0.005 u'v' units) and 1 condition without chromatic noise. We observed that trichromats had an increasing luminance threshold as a function of chromatic noise saturation under all chromatic noise conditions. The subjects with color vision deficiencies displayed no changes in the luminance threshold across the different chromatic noise saturations when the noise was composed of chromaticities close to their color confusion lines (protan and deutan chromatic noise). However, for tritan chromatic noise, they were found to have similar results to the trichromats. The use of chromatic noise masking on luminance threshold estimates could help to simultaneously examine the processing of luminance and color information. A comparison between luminance contrast discrimination obtained from no chromatic and high-saturated chromatic noise conditions could be initially undertaken in this double-duty test.

Evaluation of the color vision acuity pattern of undergraduates of health courses in a Brazilian university / Avaliação do padrão de acuidade visual para cores de acadêmicos da área de saúde em Universidade brasileira

ABSTRACT Objective: The goal of the study is to analyze the color vision acuity pattern in undergraduates of health courses and to discuss the impact of these diseases in this population. Color deficiencies interfere significantly in the daily routine of professionals in the health area who need to discern different color hues in several situations of their everyday practice. Methods: Sixty-four volunteers, undergraduates of health courses of the Federal University of Alfenas (UNIFAL-MG), participated in the study. One man was excluded because he did not fit the inclusion criteria. Two groups were analyzed according to sex with the Farnsworth Munsell 100-Hue test. Results: There were no significant differences between the eyes and between the groups analyzed. The color vision acuity pattern is between 35 and 40, according to the Total Error Score. The gender issue does not influence the general pattern of the color vision acuity of the health courses undergraduates when those with color vision disorders are removed. Conclusion: Screenings and guidance should be given to undergraduates of health courses so that, aware of their condition of presenting some type of color disorder, they shall make the appropriate decision on which career to follow so that such limitation does not interfere with the quality of their daily life.

RESUMO Objetivo: O objetivo do estudo é analisar a acuidade visual média para cores de estudantes da área de saúde e discutir o impacto das doenças que a afetam nessa população. Deficiências cromáticas interferem de forma significativa no dia a dia de profissionais da área da saúde que necessitam de discernir diferentes matizes em diversas situações de sua prática profissional. Métodos: Participaram da pesquisa 64 voluntários, estudantes de cursos da área de saúde da Universidade Federal de Alfenas, sendo que 1 homem foi excluído por não se adequar aos critérios de inclusão. Dois grupos foram analisados, de acordo com o sexo, com o teste de Farnsworth Munsell 100-Hue. Resultados: Não houve diferenças significativas entre os olhos e entre os grupos analisados. O padrão de visão de cores encontra-se entre 35 e 40, de acordo com a Pontuação do Erro Total. A questão de gênero não influencia no padrão geral da qualidade de visão de cores de estudantes da área de saúde, quando retirados aqueles que apresentam distúrbios da visão cromática. Conclusão: Devem ser realizadas triagens e orientação para estudantes de cursos da área de saúde para que, cientes da sua condição de apresentar algum tipo de distúrbio cromático, possam tomar a decisão adequada sobre qual carreira seguir para que tal limitação não interfira na qualidade de sua vida diária.

Translucence perception is not dependent on cortical areas critical for processing colour or texture.

Translucence is an important property of natural materials, and human observers are adept at perceiving changes in translucence. Perceptions of different material properties appear to arise from different cortical regions, and it is therefore plausible that the perception of translucence is dependent on specialised regions, separate from those important for colour and texture processing. To test for anatomical independence between areas necessary for colour, texture and translucence perception we assessed translucency perception in a cortically colour blind observer, who performs at chance on tasks of colour and texture discrimination. Firstly, in order to establish that MS has shown no significant recovery, we assessed his colour perception performance on the Farnsworth-Munsell 100 Hue Test. Secondly, we tested him with two translucence ranking tasks. In one task, stimuli were images of glasses of tea varying in tea strength. In the other, stimuli were glasses of tea varying only in milkiness. MS was able to systematically rank both strength and milkiness, although less consistently than controls, and for tea strength his rankings were in the opposite order. An additional group of controls tested with greyscale versions of the images succeeded at the tasks, albeit slightly less consistently on the milkiness task, showing that the performance of normal observers cannot be transformed into the performance of MS simply by removing colour information from the stimuli. The systematic performance of MS suggests that some aspects of translucence perception do not depend on regions critical for colour and texture processing.

Behavioural and emotional issues among primary school pupils with congenital colour vision deficiency in the Federal Territory of Kuala Lumpur, Malaysia: A case-control study.

Background: Congenital colour vision deficiency (CCVD) is an untreatable disorder which has lifelong consequences. Increasing use of colours in schools has raised concern for pupils with CCVD. This case-control study was conducted to compare behavioural and emotional issues among age, gender and class-matched pupils with CCVD and normal colour vision (NCV). Methods: A total of 1732 pupils from 10 primary schools in the Federal Territory of Kuala Lumpur were screened, of which 46 pupils (45 males and 1 female) had CCVD. Mothers of male pupils with CCVD (n=44) and NCV (n=44) who gave consent were recruited to complete a self-administered parent report form, Child Behaviour Checklist for Ages 4-18 (CBCL/ 4-18) used to access behavioural and emotional problems. The CBCL/ 4-18 has three broad groupings: Internalising, Externalising and Total Behaviour Problems. Internalising Problems combines the Withdrawn, Somatic Complaints and Anxiety/ Depression sub constructs, while Externalising Problems combines the Delinquent and Aggressive Behaviour sub constructs. Results: Results from CBCL/ 4-18 showed that all pupils from both groups had scores within the normal range for all constructs. However, results from the statistical analysis for comparison, Mann-Whitney U test, showed that pupils with CCVD scored significantly higher for Externalising Problems (U=697.50, p=0.02) and Total Behaviour Problems (U=647.00, p= 0.01). Significantly higher scores were observed in Withdrawn (U=714.00, p=0.02), Thought Problems (U=438.50, p<0.001) and Aggressive Behaviour (U=738.00, p=0.04). Odds ratios, 95% CI, showed significant relative risk for high Total Behaviour Problem (OR:2.39 ,CI:1.0-5.7), Externalising Problems (OR:2.32, CI:1.0-5.5), Withdrawn (OR:2.67, CI:1.1-6.5), Thought Problems (OR:9.64, CI:3.6-26.1) and Aggressive Behaviour (OR:10.26, CI:3.4-31.0) scores among pupils with CCVD. Conclusion: Higher scores among CCVD pupils indicates that they present more behavioural and emotional problems compared to NCV pupils. Therefore, school vision screenings in Malaysia should also include colour vision to assist in the early clinical management of CCVD children.

Psychosocial aspects of colour vision deficiency: Implications for a career in medicine.

Colour vision deficiency (CVD) is a common problem and persons with CVD experience difficulties in daily life, early learning and development, education, choice of careers and work performance. Medical professionals with CVD also report difficulties in everyday tasks, training in medicine and performance of medical duties. However, because of limited evidence, the real impact of CVD on the lives of medical professionals is unclear, especially regarding the practice of medicine by doctors. The nature and severity of CVD, awareness of its impact, personal circumstances and the ability to cope with the deficiency are the major factors that determine the impact of CVD. However, there is a paucity of methodologically sound research on social and psychological aspects of CVD. Currently, early detection, enhancing awareness and offering support are the only proven ways of helping medical professionals with CVD. With the growing emphasis on equality and inclusivity of those with deficiencies, it is desirable to strike a balance between concerns about patient care and the rights of medical professionals with CVD to pursue their careers. Therefore, any future research also needs to focus on psychological aspects of CVD while exploring its impact on a career in medicine.

Development and validation of a questionnaire assessing the quality of life impact of Colour Blindness (CBQoL).

BACKGROUND: Congenital colour vision deficiency (CVD), commonly called 'colour blindness', affects around 8% of men and 0.4% of women. Although many aspects of health (e.g. change in colour of urine) and healthcare (e.g. coloured medication, colour-coded diagnostic tests), and modern life depend upon colour coding (e.g. graphs, maps, signals), the impact of colour blindness on everyday life is not generally considered a topic of importance. This study is the first to create and validate a questionnaire measuring the quality of life (QoL) impact of being colour blind. METHODS: This study consisted of two phases. Firstly, the questionnaire design and development phase was led by an expert panel and piloted on a focus group. Secondly, an online sample of 128 men and 291 women filled in the questionnaire, and the psychometric properties of the questionnaire were analysed using principal components analysis (PCA). The scores of colour blind (CB) participants and normal-sighted controls, controlling for age and sex, were compared using matched t-tests. RESULTS: The PCA resulted in a questionnaire with three domains (or subscales): QoL for Health & Lifestyle, QoL for Work, and QoL for Emotions. Controlling for age, there was a significantly greater negative impact on QoL for CB people than normal-sighted controls in regards to confusion over colour in various aspects of their health (p = 5 × 10-7), work (p = 1.3 × 10-7), and emotional life (p = 6 × 10-5). CONCLUSION: Colour blindness can significantly impact quality of life for health, emotions, and especially careers. The tool developed here could be useful in future clinical studies to measure changes in CBQoL in response to therapy in conditions where colour vision is affected. We also discuss ways in which everyday problems related to colour vision might be reduced, for example, workplaces could avoid colour coding where a non-colour alternative is possible.

Do dichromats see colours in this way? Assesing simulation tools without colorimetric measurements / ¿Son estos los colores que ven los dicrómatas? Evaluando herramientas de simulación sin mediciones colorimétricas

BACKGROUND: Simulcheck evaluates Colour Simulation Tools (CSTs, they transform colours to mimic those seen by colour vision deficients). Two CSTs (Variantor and Coblis) were used to know if the standard Simulcheck version (direct measurement based, DMB) can be substituted by another (RGB values based) not requiring sophisticated measurement instruments. METHOD: Ten normal trichromats performed the two psychophysical tasks included in the Simulcheck method. The Pseudoachromatic Stimuli Identification task provided the huv (hue angle) values of the pseudoachromatic stimuli: colours seen as red or green by normal trichromats but as grey by colour deficient people. The Minimum Achromatic Contrast task was used to compute the LR (relative luminance) values of the pseudoachromatic stimuli. RESULTS AND CONCLUSIONS: Simulcheck DMB version showed that Variantor was accurate to simulate protanopia but neither Variantor nor Coblis were accurate to simulate deuteranopia. Simulcheck RGB version provided accurate huv values, so this variable can be adequately estimated when lacking a colorimeter -an expensive and unusual apparatus-. Contrary, the inaccuracy of the LR estimations provided by Simulcheck RGB version makes it advisable to compute this variable from the measurements performed with a photometer, a cheap and easy to find apparatus

ANTECEDENTES: Simulcheck evalúa Herramientas de Simulación del Color (HSCs, transforman los colores para imitar lo que ven las personas con deficiencias en la visión cromática). Se utilizaron dos HSCs (Variantor y Coblis) para evaluar si la versión estándar de Simulcheck (basada en mediciones directas, BMD) puede sustituirse por otra que no requiere instrumentos de medición sofisticados (basada en valores RGB). MÉTODO: diez tricrómatas realizaron las tareas psicofísicas incluidas en el método Simulcheck. La de Identificación de Estímulos Pseudoacromáticos proporcionó el ángulo cromático (huv) de los estímulos que los observadores comunes ven rojos o verdes, pero grises las personas con deficiencias en la visión cromática. La de Mínimo Contraste Acromático proporcionó los valores LR (luminancia relativa) de los estímulos pseudoacromáticos. RESULTADOS Y CONCLUSIONES: la versión BMD mostró que Variantor simuló adecuadamente la protanopia, pero que ni Variantor ni Coblis fueron adecuados para la deuteranopia. La Versión RGB del método Simulcheck proporcionó valores huv adecuados, consecuentemente se concluyó que esta variable puede estimarse adecuadamente sin un colorímetro -aparato caro e inusual-. Por el contrario, la inadecuación de las estimaciones de LR proporcionadas por la versión RGB recomienda computar esta variable usando mediciones realizadas con un fotómetro, un aparato barato y fácil de encontrar

Ocular Diseases Among Pathologists and Pathologists' Perceptions on Ocular Diseases: A Survey Study.

OBJECTIVE: The impact of visual disorders and color vision deficiency on the occupational life has been previously investigated by several studies. In this study, we aimed to evaluate the prevalence of visual disorders among Turkish pathologists and their perceptions on visual disorders. MATERIAL AND METHOD: A survey composed of 14 questions about ocular diseases and perceptions to these diseases has been introduced to the volunteering pathologists or pathology residents, participating in the 23rd Congress of Pathology. RESULTS: Ninety-three pathologists or pathology residents participated in the survey. Of the participants, 25 (26.9%) were residents, 30 (32.3%) were pathology specialists, and 36 (38.7%) were academicians. The mean duration for working as a pathologist was 15 years. The vast majority (%93.5) of the participants had at least one type of refractive error; the two most common disorders were myopia (77.0%) and astigmatism (64.4%). Sixty-four of the participants (68.8%) claimed an increase in their refractive error after working in the pathology department. Eyeglasses (56/87, 64.4%), contact lenses (14/87, 16.1%), or both (9/87, 10.3%) were used in order to correct the refractive error; however, only 31 of the participants (33.3%) preferred using eyeglasses during microscopy. While 65 participants (69.9%) never had conjunctivitis, 26 participants (28.0%) had at least one conjunctivitis attack. None of the participants claimed to be color blind. CONCLUSION: Conjunctivitis and refractive errors are quite prevalent among pathologists. Refractive errors were also found to increase during the pathology practice. Most of the pathologists do not consider visual disorders (mostly refractive errors) as a negative factor during their career decision making, except a color vision defect.

Colour vision impairment is associated with disease severity in multiple sclerosis.

BACKGROUND: Colour vision assessment correlates with damage of the visual pathway and might be informative of overall brain damage in multiple sclerosis (MS). OBJECTIVE: The objective of this paper is to investigate the association between impaired colour vision and disease severity. METHODS: We performed neurological and ophthalmic examinations, as well as magnetic resonance imaging (MRI) and optical coherence tomography (OCT) analyses, on 108 MS patients, both at baseline and after a follow-up of one year. Colour vision was evaluated by Hardy, Rand and Rittler plates. Dyschromatopsia was defined if colour vision was impaired in either eye, except for participants with optic neuritis (ON), for whom only the unaffected eye was considered. We used general linear models adjusted for sex, age, disease duration and MS treatment for comparing presence of dyschromatopsia and disease severity. RESULTS: Impaired colour vision in non-ON eyes was detected in 21 out of 108 patients at baseline. At baseline, patients with dyschromatopsia had lower Multiple Sclerosis Functional Composite (MSFC) scores and Brief Repeatable Battery-Neuropsychology executive function scores than those participants with normal colour vision. In addition, these patients had thinner retinal nerve fiber layer (RNFL), and smaller macular volume, normalized brain volume and normalized gray matter volume (NGMV) at baseline. Moreover, participants with incident dyschromatopsia after one-year follow-up had a greater disability measured by the Expanded Disability Status Scale and MSFC-20 and a greater decrease in NGMV than participants with normal colour vision. CONCLUSIONS: Colour vision impairment is associated with greater MS severity.

Role-play experience facilitates reading the mind of individuals with different perception.

The present study examined effects of role-play experience on reading the mind of people with different perception. It is normally difficult but very important in daily life to understand people with different characteristics, including those with restricted color vision. We explored the mechanisms of reading the mind of people with different perception. Forty university students were introduced to a communication task in which the use of mindreading was essential. During each trial, participants viewed a shelf, presented on a laptop computer, which contained several familiar objects, and they were instructed to touch an object on the shelf following an instruction issued by a partner who stood at the opposite side of the shelf. There were two partners: one was a monkey with normal color vision and the other was a dog with restricted color vision. The monkey could see all the objects in the same colors as the participants, whereas the dog saw some objects in different colors (e.g., he saw as yellow objects that the participants saw as red). Participants were required to respond according to the partner's instruction. In the restricted color vision condition, the dog saw the colors of objects differently; thus, participants had to work out his intentions (i.e., mind read), according to his different perspective. In the normal color vision condition, all objects were in the same colors as those seen by the monkey. Before the test phase, the role-play group had a role-play experience in which participants assumed the role of people with restricted color vision. No-role-play participants made significantly more errors in the restricted color vision condition than in the normal color vision condition, whereas among role-play participants, there was no difference between conditions. These results suggest that role-play experience facilitates reading the mind of people with perceptual experiences different from our own.

Does dichromatic color simulation predict color identification error rates?

PURPOSE: Several algorithms are available to transform colored digital images into simulated dichromatic color perception. These algorithms can be very illustrative of the problems dichromats experience in discriminating colors. The purpose of this study was to determine whether one type of transformation could provide a quantitative account of error rates in identifying colors displayed on a computer monitor. METHODS: The experimental task required observers to identify the color of small rectangles displayed on a computer monitor within a black background. There were eight colors. The number of errors for each color was recorded. Four deuteranopes and five protanopes participated. Color differences were calculated using normal trichromatic and dichromatic values. The dichromatic color differences were calculated using the procedure developed by Brettel et al. [J Opt Soc Am (A) 1997;14:2647-55]. RESULTS: The relationship between error rates and color differences calculated in either color space was fit by an exponential decay function. However, the fit provided by the dichromatic color differences was no better than that using color differences calculated in trichromatic color space and both regressions could only account for approximately 30% of the variance in the data. CONCLUSIONS: Correlations between the error rates in identifying colors for dichromats and color differences were low-to-moderate whether the color differences were based on normal trichromatic color space or a dichromatic transformation. This finding suggests that it may be sufficient to calculate the color difference only in color-normal space to determine whether the colors will be confused by a person with a congenital color vision defect. Although computer algorithms are useful in illustrating color discrimination problems experienced by dichromats, they may not offer any advantage over typical trichromatic color spaces in predicting performance in color identification. The lack of any advantage may be due to how dichromats use brightness information to identify colors.

Simulations of adaptation and color appearance in observers with varying spectral sensitivity.

A model of adaptation and visual coding was used to simulate how color appearance might vary among individuals that differ only in their sensitivity to wavelength. Color responses to images were calculated for cone receptors with spectral sensitivities specific to the individual, and in postreceptoral mechanisms tuned to different combinations of the cones. Adaptation was assumed to normalize sensitivity within each cone and postreceptoral channel so that the average response to an ensemble of scenes equaled the mean response in channels defined for the reference observer. Image colors were then rendered from the adapted channels' outputs. The transformed images provide an illustration of the variations in color appearance that could be attributed to differences in spectral sensitivity in otherwise identical observers adapted to identical worlds, and examples of these predictions are shown for both normal variation (e.g. in lens and macular pigment) and color deficiencies (anomalous trichromacy). The simulations highlight the role that known processes of adaptation may play in compensating color appearance for variations in sensitivity both within and across observers, and provide a novel tool for visualizing the perceptual consequences of any variation in visual sensitivity including changes associated with development or disease.

Colour rendering of indoor lighting with CIE illuminants and white LEDs for normal and colour deficient observers.

The goal of this work was to evaluate the colour rendering of indoor lighting with CIE illuminants and white LEDs by estimating the chromatic diversity produced for normal and colour deficient observers. Reflectance spectra of a collection of scenes made of objects typically found indoors were obtained with hyperspectral imaging. Chromatic diversity was computed for 55 CIE illuminants and five LED light sources by estimating the number of different colours perceived in the scenes analysed. A considerable variation in chromatic diversity was found across illuminants, with the best producing about 50% more colours than the worst. For normal observers, the best illuminant was CIE FL3.8 which produced about 8% more colours than CIE illuminant A and D(65); for colour deficient observers, the best illuminants varied with the type of deficiency. When the number of colours produced with a specific illuminant was compared against its colour rendering index (CRI) and gamut area index (GAI), weak correlations were obtained. Together, these results suggest that normal and colour deficient observers may benefit from a careful choice of the illuminant, and this choice may not necessarily be based only on the CRI or GAI.

Unilateral colour vision defects and the dimensions of dichromat experience.

The standard view, that protanopes and deuteranopes see only varieties of yellow and blue, is often taken to be supported by the reports of people with one colour-blind eye and one normal (or near-normal) eye. Judd's survey of 89 years of unilateral cases might seem authoritative: 'The color perceptions of both protanopic and deuteranopic observers are confined to two hues, yellow and blue', corresponding to 575 and 470 nm (DB Judd, J Research National Bureau Standards, 41: 247-271, 1948). A critical re-examination reveals, however, that the cases do not support Judd's claim: the original publications indicate in most cases substantial (though limited) red-green discrimination with the dichromatic eye under favourable conditions (e.g. with large fields), and evidence of red/green sensation; in the main case where researchers find sensation only of yellow and blue, it is by using experimental methods that are almost guaranteed not to reveal the full range of the subject's sensation. More recent reports (from the 1950s and later) show that, if the colour experience space of a dichromat eye collapses to a 2D slice through the 3D space of a normal trichromat, the slice may be not flat but curved (and curved in more than one dimension): there are further reasons to think that dichromat colour experience, whether unilateral or bilateral, may not collapse to a plane at all. The unilateral cases are unclear in many ways, but they certainly give no support to a 'yellow-and-blue' view of dichromat experience.

Quantitative assessment of commercial filter 'aids' for red-green colour defectives.

The claims made for 43 commercial filter 'aids', that they improve the colour discrimination of red-green colour defectives, are assessed for protanomaly and deuteranomaly by changes in the colour spacing of traffic signals (European Standard EN 1836:2005) and of the Farnsworth D15 test. Spectral transmittances of the 'aids' are measured and tristimulus values with and without 'aids' are computed using cone fundamentals and the spectral power distributions of either the D15 chips illuminated by CIE Illuminant C or of traffic signals. Chromaticities (l,s) are presented in cone excitation diagrams for protanomaly and deuteranomaly in terms of the relative excitation of their long (L), medium (M) and short (S) wavelength-sensitive cones. After correcting for non-uniform colour spacing in these diagrams, standard deviations parallel to the l and s axes are computed and enhancement factors E(l) and E(s) are derived as the ratio of 'aided' to 'unaided' standard deviations. Values of E(l) for traffic signals with most 'aids' are <1 and many do not meet the European signal detection standard. A few 'aids' have expansive E(l) factors but with inadequate utility: the largest being 1.2 for traffic signals and 1.3 for the D15 colours. Analyses, replicated for 19 'aids' from one manufacturer using 658 Munsell colours inside the D15 locus, yield E(l) factors within 1% of those found for the 16 D15 colours.

Colour change in cyanosis and the confusions of congenital colour vision deficient observers.

Visual recognition of cyanosis is an important clinical activity. While pulse oximetry is almost universal in the hospital environment, there are circumstances where it is not available or may be unreliable. Cyanosis recognition is affected by lighting colour. In addition, there is, mainly anecdotal, evidence that people with greater colour vision deficiencies (CVDs) have particular difficulty and there is no effective lighting strategy to assist in the observation. The change of blood colour with oxygenation has been shown to lie close to the direction of colour confusions made by congenital red-green dichromats. The important sites of observation are lips, nail beds and palm creases. 10 subjects who were known to be chronically hypoxaemic were recruited from the chronic respiratory program. Their blood oxygen saturation (SpO(2)) varied from 84% to 96% pre-exercise, and 61-84% post-exercise. Ten normal subjects were recruited whose SpO(2) was 99% or 100%. The spectral radiances of lips, nail beds and palm creases were measured using a telespectroradiometer and compared with the spectral radiances of a white tile of known spectral reflectances measured in the same location. This is a non-contact method of measurement, avoiding the blanching caused by pressure of contact methods. The spectral reflectances were calculated, and the chromaticities calculated for a Planckian radiator T = 4000K. Measurements on lips yielded the most consistent results. The colour changes pre- and post-exercise and compared with normal colour lie generally along a deutan confusion line. These results show the direction of the colour change and confirm the, previously anecdotal, difficulties in detecting cyanosis by observers with CVDs.

Color vision impairment in type 2 diabetes assessed by the D-15d test and the Cambridge Colour Test.

Color vision impairment emerges at early stages of diabetes mellitus type 2 (DM2) and may precede diabetic retinopathy or the appearance of vascular alterations in the retina. The aim of the present study was to compare the evaluation of the color vision with two different tests - the Lanthony desaturated D-15d test (a traditional color arrangement test), and the Cambridge Colour Test (CCT) (a computerized color discrimination test) - in patients diagnosed with DM2 without clinical signs of diabetic retinopathy (DR), and in sex- and age-matched control groups. Both color tests revealed statistically significant differences between the controls and the worst eyes of the DM2 patients. In addition, the degree of color vision impairment diagnosed by both tests correlated with the disease duration. The D-15d outcomes indicated solely tritan losses. In comparison, CCT outcomes revealed diffuse losses in color discrimination: 13.3% for best eyes and 29% for worst eyes. In addition, elevation of tritan thresholds in the DM2 patients, as detected by the Trivector subtest of the CCT, was found to correlate with the level of glycated hemoglobin. Outcomes of both tests confirm that subclinical losses of color vision are present in DM2 patients at an early stage of the disease, prior to signs of retinopathy. Considering the advantages of the CCT test compared to the D-15d test, further studies should attempt to verify and/or improve the efficiency of the CCT test.

Color-space distortions following long-term occupational exposure to mercury vapor.

Color vision was examined in subjects with long-term occupational exposure to mercury (Hg) vapor. The color vision impairment was assessed by employing a quantitative measure of distortion of individual and group perceptual color spaces. Hg subjects (n = 18; 42.1 ± 6.5 years old; exposure time = 10.4 ± 5.0 years; time away from the exposure source = 6.8 ± 4.6 years) and controls (n = 18; 46.1 ± 8.4 years old) were examined using two arrangement tests, D-15 and D-15d, in the traditional way, and also in a triadic procedure. From each subject's 'odd-one-out' choices, matrices of inter-cap subjective dissimilarities were derived and processed by non-metric multidimensional scaling (MDS). D-15d results differed significantly between the Hg-group and the control group (p < 0.05), with the impairment predominantly along the tritan axis. 2D perceptual color spaces, individual and group, were reconstructed, with the dimensions interpreted as the red-green (RG) and the blue-yellow (BY) systems. When color configurations from the Hg-group were compared to those of the controls, they presented more fluctuations along both chromatic dimensions, indicating a statistically significant difference along the BY axis. In conclusion, the present findings confirm that color vision impairments persist in subjects that have received long-term occupational exposure to Hg-vapor although, at the time of testing, they were presenting mean urinary concentration within the normal range for non-exposed individuals. Considering the advantages of the triadic procedure in clinical evaluation of acquired color vision deficiencies, further studies should attempt to verify and/or improve its efficacy.

Anosognosia for cerebral achromatopsia--a longitudinal case study.

Cerebral achromatopsia is a rare disorder of colour vision caused by bilateral damage to the occipito-temporal cortex. Patients with cerebral achromatopsia are commonly said to suffer due to their disturbed colour sense. Here, we report the case of a patient with cerebral achromatopsia who was initially unaware of his deficit, although three experiments with eye movement recordings demonstrated his severe inability to use colour information in everyday tasks. During two months, the evolution of his colour vision deficit was followed with repeated standardized colour vision tests and eye movement recordings. While his performance continuously improved, he became more and more aware of the deficit. Only after colour vision had almost normalized, his subjective colour sensation was inconspicuous again. The simultaneous occurrence of achromatopsia and the corresponding anosognosia and their parallel recovery suggest that both deficits were due to dysfunction of the same brain region. Consequently, the subjective experience of colour loss in achromatopsia may depend on the residual function of the damaged colour centre.