Color Discrimination Thresholds Research Articles

Color discrimination repetition distorts color representations

Perceptual learning is the improvement of perceptual performance after repeated practice on a perceptual task. Studies on perceptual learning in color vision are limited. In this study, we measured the impact of color discrimination repetitions at a specific base color on color perception for entire hues. Participants performed five sessions of color discrimination training (200 or 300 trials per session) over five days, at colors on either the negative or positive direction of the L-M color axis, based on group assignment. We administered three color perception assessments (unique hues, color category boundaries, and color appearance) before and after the sessions to evaluate perceptual changes after training. The results showed declines in color discrimination thresholds after training, as expected. Additionally, the training influenced outcomes across all three assessment types. After the training, the perceived color appearance changed near the trained color along the stimulus hue, and some of the unique hues and the color category boundaries moved significantly toward the trained color. These findings indicate that short-term repetitions of color discrimination training can alter color representations in the visual system, distorting color perception around the trained color.

Ultraviolet vision in anemonefish improves colour discrimination.

In many animals, ultraviolet (UV) vision guides navigation, foraging, and communication, but few studies have addressed the contribution of UV signals to colour vision, or measured UV discrimination thresholds using behavioural experiments. Here, we tested UV colour vision in an anemonefish (Amphiprion ocellaris) using a five-channel (RGB-V-UV) LED display. We first determined that the maximal sensitivity of the A. ocellaris UV cone was ∼386 nm using microspectrophotometry. Three additional cone spectral sensitivities had maxima at ∼497, 515 and ∼535 nm. We then behaviourally measured colour discrimination thresholds by training anemonefish to distinguish a coloured target pixel from grey distractor pixels of varying intensity. Thresholds were calculated for nine sets of colours with and without UV signals. Using a tetrachromatic vision model, we found that anemonefish were better (i.e. discrimination thresholds were lower) at discriminating colours when target pixels had higher UV chromatic contrast. These colours caused a greater stimulation of the UV cone relative to other cone types. These findings imply that a UV component of colour signals and cues improves their detectability, which likely increases the prominence of anemonefish body patterns for communication and the silhouette of zooplankton prey.

Poster Session II: Spillover effects of color discrimination training on color category boundaries and color appearance.

Perceptual learning refers to the increase in perceptual sensitivity that results from several days of training on a perceptual task. Although perceptual learning has been shown to be effective in a variety of perceptual tasks, few studies have examined perceptual learning in color perception. In this study, we investigated how color discrimination training at a base color affected various aspects of color perception for entire hues. The training consisted of five days of S color discrimination (300 trials/day) at either the negative or positive L-M base color, depending on the observer groups. Before and after the training, three types of color perception tests (color difference, unique hue, and color category boundary) were conducted for colors with various hues to examine the changes in color perception due to the training. The results showed that the color discrimination thresholds in the training decreased as expected with repeated trials. Interestingly, the training also affected the performance of the three types of tests; the perceived color difference around the training color tended to increase, and some of the unique hues and the color category boundaries shifted significantly toward the training color. These results suggest that only a few days of color discrimination training can spill over to the entire color space and induce distortion of the perceptual color space.

Impairment of visual and neurologic functions associated with agrochemical use.

To determine whether exposure to occupational levels of agrochemicals is associated with a range of low- (contrast and colour) and higher-level visual functions, particularly the detection of global form and motion coherence. We compared the performance of workers exposed to occupational levels of pesticides and non-exposed individuals on visual tasks that measured colour discrimination (Farnsworth Munsell 100 and Lanthony D15 desaturated) and the contrast sensitivity function (1-16 cpd). Global form and motion detection thresholds were measured using Glass-pattern and global dot motion stimuli. Neurotoxicity symptoms and biological markers associated with pesticide exposure were quantified using the Q16 modified questionnaire and via tests for levels of acetylcholinesterase in blood and substance P from the tear film, respectively. Workers exposed to pesticides had significantly more neurotoxic symptoms than non-exposed workers. No significant difference between groups for acetylcholinesterase levels was found, but there was a significant group difference in Substance P. The exposed group also had significantly poorer contrast sensitivity, colour discrimination and higher coherence detection thresholds for global form and motion perception. Exposure to occupational levels of agrochemicals in workers with signs of neurotoxicity is associated with low and high visual perception deficits.

Investigation on the equi‐depth of color depth formulas based on color discrimination threshold and acceptable tolerance

AbstractAccurate characterization of color depth is important for assessing a dye's relative strength, color fastness, and so on. There are several formulas for color depth, however, with evaluation effects that are quite different. In this study, we attempt to investigate the equi‐depth properties of the color depth formulas so as to provide a reference for selection. One thousand two hundred and six color samples were dyed around six standard depths of three hues in SDC Standard Depth Scales. Sixteen observers were recruited for “Pass–Fail” psychophysical experiments. More than 30 000 experimental data points were obtained to calculate the values of discrimination thresholds and acceptable tolerances at six different standard depths for each formula. The equi‐depth properties of five main color depth formulas were statistically analyzed through their coefficients of variation (CV)% values. Results show that the Yang3 formula is optimal for both color depth discrimination threshold and acceptable tolerance, and its average wrong decision is less than the minimum wrong decision of all observers, as well as those of the other four formulas. Overall, Yang3 formula shows the best equi‐depth and highest relatively accuracy among the five formulas.

Color discrimination threshold of human vision for textiles under different illumination conditions

In this work, the varying color discrimination thresholds of human vision for textiles with a wide range of physical color attributes under different illumination conditions were examined. It was found that, regardless of the illumination condition and the color attributes of the textiles, people cannot generally perceive the color differences of textiles smaller than 4.25 Δ E*ab. Meanwhile, the color discrimination threshold was found to be significantly affected by the illuminance of illuminants and all the physical color attributes of lightness, chroma, and hue of the textiles observed. People were generally better able to distinguish color differences in bright environments with the illuminance of 2000 lux than in darker ones with 100 lux. In addition, color differences between dark and less-saturated textiles were found to be generally easier to be perceived than those between light and saturated textiles under various illuminants. In addition, regardless of the illuminant, color differences between neutral colored textiles were easier to be perceived than those between chromatic colored textiles with the mean color discrimination threshold of 2.85 and 4.42 Δ E*ab, respectively. In particular, among chromatic colored textiles, color differences between yellow textiles were generally the hardest to be perceived with the mean threshold of 5.58 Δ E*ab.

Newly learned shape-color associations show signatures of reliability-weighted averaging without forced fusion or a memory color effect.

Reliability-weighted averaging of multiple perceptual estimates (or cues) can improve precision. Research suggests that newly learned statistical associations can be rapidly integrated in this way for efficient decision-making. Yet, it remains unclear if the integration of newly learned statistics into decision-making can directly influence perception, rather than taking place only at the decision stage. In two experiments, we implicitly taught observers novel associations between shape and color. Observers made color matches by adjusting the color of an oval to match a simultaneously presented reference. As the color of the oval changed across trials, so did its shape according to a novel mapping of axis ratio to color. Observers showed signatures of reliability-weighted averaging-a precision improvement in both experiments and reweighting of the newly learned shape cue with changes in uncertainty in Experiment 2. To ask whether this was accompanied by perceptual effects, Experiment 1 tested for forced fusion by measuring color discrimination thresholds with and without incongruent novel cues. Experiment 2 tested for a memory color effect, observers adjusting the color of ovals with different axis ratios until they appeared gray. There was no evidence for forced fusion and the opposite of a memory color effect. Overall, our results suggest that the ability to quickly learn novel cues and integrate them with familiar cues is not immediately (within the short duration of our experiments and in the domain of color and shape) accompanied by common perceptual effects.

Effect of filters on the accommodation and colour discrimination

AbstractPurpose: To evaluate the effect of coloured filters on the accommodative response and colour discrimination in young subjects.Methods: Two long pass filters (LED light reduction and 511 nm filter), two selective absorption filters (ML41 and emerald filter), and no filter condition were evaluated. The photorefractor PowerRef3 (PlusOptix) was used to measure the objective refraction at 3 different distances (40, 100, and 400 cm). The measurement obtained at 400 cm was used as a reference to calculate the accommodative response. The fixation target consisted of five letter length words (size corresponding to 6/12 Snellen) that were presented in black font over white background. Words changed with a frequency of 2 Hz according to the rapid serial visual presentation paradigm. The Cambridge Colour Test (Metropsis) was used to measure the discrimination threshold in a 10‐vector ellipse at a 3 m viewing distance. The measurement was repeated twice, and it was performed monocularly. In total, 20 healthy volunteers with no accommodation problems or colour blindness were included.Results: On average, the accommodative response with no filter condition was larger compared to the measurements with filters for 40 and 100 cm. The differences were in all cases lower than 0.25D, and differences were not statistically significant (p > 0.05). For the colour discrimination thresholds, the ML41 and 511 filters showed statistically significant different values compared to the other two conditions for most of the vectors. The filter 511 had the highest impact on the colour vision, as the results resemble to a Tritan defect.Conclusions: The accommodative response in healthy young adults was not significantly different than the no filter condition. The colour discrimination thresholds with the filter ML41 and 511 were significantly different compared to the no filter condition.

Line element for the perceptual color space.

It is generally accepted that the perceptual color space is not Euclidean. A new line element for a 3-dimensional Riemannian color space was developed. This line element is based on the Friele line elements and psychophysical color discrimination models, and comprises both the first and second stage of color vision. The line element is expressed in a contrast space based on the MacLeod-Boynton chromaticities. New equations for the contrast thresholds along the cardinal axes and new metric tensor elements were determined. Visual adaptation effects were incorporated into the model. Color discrimination threshold ellipsoids were calculated with the new line element. Adequate agreement with experimental threshold ellipsoids reported in literature was demonstrated. From a comparison with other color difference metrics a better overall predictability of threshold ellipsoids was found with the new line element.

Colour discrimination thresholds vary throughout colour space in a reef fish (Rhinecanthus aculeatus)

ABSTRACTAnimals use colour vision in a range of behaviours. Visual performance is limited by thresholds, which are set by noise in photoreceptors and subsequent neural processing. The receptor noise limited (RNL) model of colour discrimination is widely used for modelling colour vision and accounts well for experimental data from many species. In one of the most comprehensive tests yet of colour discrimination in a non-human species, we used Ishihara-style stimulus patterns to examine thresholds for 21 directions at five locations in colour space for the fish Rhinecanthus aculeatus. Thresholds matched RNL model predictions most closely for stimuli near the achromatic point, but exceeded predictions (indicating a decline in sensitivity) with distance from this point. Thresholds were also usually higher for saturation than for hue differences. These changes in colour threshold with colour space location and direction may give insight into photoreceptor non-linearities and post-receptoral mechanisms of colour vision in fish. Our results highlight the need for a cautious interpretation of the RNL model – especially for modelling colours that differ from one another in saturation (rather than hue), and for highly saturated colours distant from the achromatic point in colour space.

Color discrimination in anomalous trichromacy: Experiment and theory

In anomalous trichromacy, the color signals available from comparing the activities of the two classes of cone sensitive in the medium and long wavelength parts of the spectrum are much reduced from those available in normal trichromacy, and color discrimination thresholds along the red-green axis are correspondingly elevated. Yet there is evidence that suprathreshold color perception is relatively preserved; this has led to the suggestion that anomalous trichromats post-receptorally amplify their impoverished red-green signals. To test this idea, we measured chromatic discrimination from white and from saturated red and green pedestals. If there is no post-receptoral compensation, the anomalous trichromat’s loss of chromatic contrast will apply equally to the pedestal and to the test color. Coupled with a compressively nonlinear neural representation of saturation, this means that a given pedestal contrast will cause a smaller than normal modulation of discrimination sensitivity. We examined cases where chromatic pedestals impair the color discrimination of normal trichromatic observers. As predicted, anomalous observers experienced less impairment than normal trichromats, though they remained less sensitive than normal trichromats. Although the effectiveness of chromatic pedestals in impairing color discrimination was less for anomalous than for normal trichromats, the chromatic pedestals were more effective for anomalous observers than would be expected if the anomalous post-receptoral visual system were the same as in normal trichromacy; the hypothesis of zero compensation can be rejected. This might suggest that the effective contrast of the pedestal is post-receptorally amplified. But on closer analysis, the results do not support candidate simple models involving post-receptoral compensation either.

Color Inconstancy of Chromatic and Achromatic Textile Fabrics with Changes in the Correlated Color Temperature and Luminance of the Light Source

This study quantitatively analyzed how the color appearance of textile fabrics of varying lightness, chroma, and hue changes under a broad spectrum of illumination conditions. The color appearances of 203 chromatic (R, YR, Y, GY, G, BG, B, and RB) and achromatic fabrics were measured spectroradiometrically under 16 light sources with different correlated color temperatures (2700, 4000, 5000, and 6500 K) and luminances (50, 100, 500, and 1000 cd/m2). The color appearance values were compared with the spectrophotometrically measured physical color values of the fabrics, which were regarded as their true colors. The differences ranged up to 12.45 ∣ΔL*10∣, 19.32 ∣ΔC*ab,10∣, 161.83∣Δhab, 10∣, and 16.70 ΔECMC(2:1) units, which were significantly higher than the color discrimination thresholds of the human eye. Among 9 hue groups of fabrics, the color appearances of BG (bluish-green) fabrics were generally most affected by light sources, while those of achromatic fabrics were least affected with mean ΔECMC(2:1) of 6.32 and 1.03, respectively. It was also found that the correlated color temperature of light sources significantly affected all the lightness, colorfulness, and hue of fabrics, and the different trends of these effects were observed for different hue groups. Unlike current knowledge, light sources with a correlated color temperature of 6500 K did not always produce color appearances that most closely resemble the actual physical colors. Meanwhile, the luminance of light sources did not have a profound effect on the color appearances of fabrics.

Pixel-Based Machine Learning and Image Reconstitution for Dot-ELISA Pathogen Diagnosis in Biological Samples.

Serological methods serve as a direct or indirect means of pathogen infection diagnosis in plant and animal species, including humans. Dot-ELISA (DE) is an inexpensive and sensitive, solid-state version of the microplate enzyme-linked immunosorbent assay, with a broad range of applications in epidemiology. Yet, its applicability is limited by uncertainties in the qualitative output of the assay due to overlapping dot colorations of positive and negative samples, stemming mainly from the inherent color discrimination thresholds of the human eye. Here, we report a novel approach for unambiguous DE output evaluation by applying machine learning-based pattern recognition of image pixels of the blot using an impartial predictive model rather than human judgment. Supervised machine learning was used to train a classifier algorithm through a built multivariate logistic regression model based on the RGB (“Red,” “Green,” “Blue”) pixel attributes of a scanned DE output of samples of known infection status to a model pathogen (Lettuce big-vein associated virus). Based on the trained and cross-validated algorithm, pixel probabilities of unknown samples could be predicted in scanned DE output images, which would then be reconstituted by pixels having probabilities above a cutoff. The cutoff may be selected at will to yield desirable false positive and false negative rates depending on the question at hand, thus allowing for proper dot classification of positive and negative samples and, hence, accurate diagnosis. Potential improvements and diagnostic applications of the proposed versatile method that translates unique pathogen antigens to the universal basic color language are discussed.

HEREDITARY NEUROPATHIES & ALS: P.107 Review of ophthalmologic findings following intrathecal gene transfer for giant axonal neuropathy

Giant Axonal Neuropathy (GAN) is an ultra-rare childhood onset neurodegenerative disorder of the peripheral and central nervous system. Recessive GAN mutations cause loss of function of gigaxonin, a cytoskeletal regulatory protein, leading to progressive sensorimotor and optic neuropathy, CNS involvement and respiratory failure. We report on the ophthalmologic findings of a single site, phase I, non-randomized, open label dose escalation gene transfer study for GAN (NCT02362438), a first-in-human intrathecal (IT) AAV9 mediated gene transfer. Data from 11 patients with GAN dosed at 3 dose levels; 3.5 × 1013 (1X), 1.2 × 1014 (3.3X), and 1.8 × 1014 (5X) with scAAV9-JeT-GAN with up to 3 years of follow up is analyzed. Ophthalmic evaluations include best-corrected visual acuity, color discrimination thresholds, fundus imaging, and measurement of retinal nerve fiber later (RNFL) thickness through optical coherence tomography. Photopic electroretinography including a photopic negative response and visual evoked potentials (VEP) were also recorded. GAN natural history study data is used for comparison of visual acuity and RNFL thickness as well as correlation of RNFL thickness with validated outcome measures of motor function. Cross sectional natural history analysis shows significant correlation between RNFL thickness and the MFM32 total score. Interim analysis reveals a trend towards stabilization and slowing of the expected decline in RNFL thickness and visual acuity compared to pre-trial lead in data and natural history. VEP results were variable with no consistent trends across natural history and clinical trial cohorts. The interim analysis of ophthalmologic assessments highlights several key aspects: 1) RNFL thickness, a structural assessment of optic nerve atrophy and axonal nerve degeneration at the level of the CNS is a biomarker strongly correlated to overall disease severity. In GAN patients, the decline in RNFL precedes change in visual acuity, and changes can be detected longitudinally. 2) The trend towards stabilization of RNFL thickness post gene transfer suggests that RNFL may be an objective and responsive biomarker of visual system involvement and overall nervous system degeneration in GAN. 3) Assessment of RNFL thickness post gene transfer may be used as an exploratory marker of feasibility of CNS transduction following IT gene transfer.

Occupational health and functional condition of the organ of vision in employees at the modern production of microelectronics

Introduction. In the emerging digital economy, microelectronics is a driver of civilizational progress, ensuring technological sovereignty, and determines the level of development of modern society. Its elemental base is continuously developing and improving in the direction of microminiaturization of electronic components and complex miniaturization of equipment. In this regard, the purpose of the study was a hygienic assessment of operational conditions and the functional state of the visual analyzer in employees working in the modern production of microchips and semiconductor devices.Material and methods. At the workplaces of the radio components collectors there were measured sound levels, artificial lighting, and microclimate parameters; air pollution by chemicals; the hardness and intensity of work are estimated based on timing observations. The functional state of the organ of vision was studied once and in the dynamics of the working day. The operation of the accommodation apparatus, as well as the state of the receptor link on the thresholds of color perception, were studied.Results. Levels of chemical and physical factors of the operational environment during assembly, sealing, and labeling operations were revealed not to be over normalized values. According to the results of timing observations, the time of use of optical instruments is from 55 to 75% of the shift, which characterizes the work process as stressful as grade 3 (harmful) 1st and 2nd degree, according to the duration of being in a fixed sitting position for more than 50% of the time, the severity of labor is estimated as grade 3 1st degree. The obtained data indicate a decrease in the volume of accommodation of the eye and an increase in color discrimination thresholds in the dynamics of the working day.Discussion. In shaping the operational conditions of workers who assemble and control products, the decisive role belongs to the hardness and intensity of the labor process, in particular, to the long-term restriction of motor activity in a fixed sitting position and the visual load associated with performing precision work using optical instruments. A change in the function of vision, characterized by a violation of the accommodative ability of the eye, a decrease in color perception, indicates the development of visual fatigue in collectors.Conclusion. Despite the modernization of production equipment, a significant proportion of labor operations for the assembly of products are carried out manually. Given the impossibility of ensuring complete automation of technological processes at the enterprises, preventive measures should be aimed at organizing a rational mode of operation that provides relief of vision.

Visual processing of color and shape in people with leprosy

The aim of this study was to analyze the contrast sensitivity of spatial luminance and the color discrimination thresholds of the protan, deutan, and tritan axes of people with leprosy. This study included 8 subjects with leprosy (M = 4, W = 4, M = 33.38 ± 8.7) and 8 healthy subjects (M = 4, W = 4, M = 30.89 ± 5.8). The contrast sensitivity was evaluated by the Metropsis software version 11.0 with vertical sinusoidal grids of frequencies of 0.2, 0.5, 1, 5, 10, and 16 cycles per degree of visual angle (cpd) and color vision by the desaturated Lanthony D15 tests and the trivector and ellipse protocols of the Cambridge Color Test. The results showed significant differences between the groups in the processing of spatial frequencies of 0.2 (U = 14; p = .018); 5.0 (U = 45.0; p = .001); 10.0 (U = 45.0; p = .001), and 16.0 (U = 45.0; p = .001) cpd. The difference in color recognition through D15d (U = 4.0; p = .002). Ellipse 2 (U = 10.0; p = .012) and ellipse 3 (U = 9.0; p = .009) were discriminated against. Overall, the results indicate that leprosy changes the visual processing of low, medium, and high spatial frequencies, as well as the sensitivity of the short wavelength (tritan line of confusion) and long (protan line of confusion) cones.

Color Difference and Thermal Stability of Flexible Transparent InGaN/GaN Multiple Quantum Wells Mini-LED Arrays

We present studies of the color uniformity and thermal stability of a flexible and transparent ${32}\times {32}$ mini-LED array on polyethylene terephthalate (PET) substrate up to a brightness rating of 5000 nits at room temperature, whose brightness is required for outdoor display applications. Surprisingly, even at 5000 nits, the temperature variation on the surface of the LED array is less than 9 °C, despite the relatively low thermal diffusivity of the polymer substrates. The average surface temperature was 33 °C. This indicates that the heat dissipation of the fabricated LED array is superior with even a polymer substrate. Further, the narrow electroluminescent (EL) emissions from the mini-LED array help to realize wider color gamut than Rec. 2020 color gamut in display applications. The color differences from the EL spectra were calculated at three different brightness. The calculated values are far less than the color discrimination threshold of the human eye corresponding to 0.005 at all testing brightness and meet the display industry requirement for color difference.

Experimental method of judging suitability of simulation model for dichromatic color appearance

There are color vision barrier-free conversion algorithms that are used to improve the contrast in images for dichromats. The algorithms focus on whether dichromats can distinguish a combination of colors and often use a simulation model of color appearance for dichromats. To adjust the algorithms for individual dichromats, it is necessary to investigate whether the simulation model used is suitable for them in the vicinity of the color discrimination threshold $${\Theta }$$; however, there have been few such studies. In this paper, we propose a method of judging the suitability of a simulation model for dichromatic color appearance in the vicinity of $${\Theta }$$ using psychophysical measurements. In our method, gradually changing colors in the RGB color space are presented (Presentation A) to a dichromat and $${\Theta }^\text {A}$$ is obtained. Moreover, colors that are simulated by a target model are also presented (Presentation B) to the dichromat and $${\Theta }^\text {B}$$ is obtained. The suitability of the simulation model for the dirchromat is quantitatively judged by comparing $${\Theta }^\text {A}$$ and $${\Theta }^\text {B}$$ using statistical methods. An application example of the proposed method is also described to concretely show the procedure of the method.

Quantitative Colour Pattern Analysis (QCPA): A comprehensive framework for the analysis of colour patterns in nature

Abstract To understand the function of colour signals in nature, we require robust quantitative analytical frameworks to enable us to estimate how animal and plant colour patterns appear against their natural background as viewed by ecologically relevant species. Due to the quantitative limitations of existing methods, colour and pattern are rarely analysed in conjunction with one another, despite a large body of literature and decades of research on the importance of spatio‐chromatic colour pattern analyses. Furthermore, key physiological limitations of animal visual systems such as spatial acuity, spectral sensitivities, photoreceptor abundances and receptor noise levels are rarely considered together in colour pattern analyses. Here, we present a novel analytical framework, called the Quantitative Colour Pattern Analysis (QCPA). We have overcome many quantitative and qualitative limitations of existing colour pattern analyses by combining calibrated digital photography and visual modelling. We have integrated and updated existing spatio‐chromatic colour pattern analyses, including adjacency, visual contrast and boundary strength analysis, to be implemented using calibrated digital photography through the Multispectral Image Analysis and Calibration (MICA) Toolbox. This combination of calibrated photography and spatio‐chromatic colour pattern analyses is enabled by the inclusion of psychophysical colour and luminance discrimination thresholds for image segmentation, which we call ‘Receptor Noise Limited Clustering’, used here for the first time. Furthermore, QCPA provides a novel psycho‐physiological approach to the modelling of spatial acuity using convolution in the spatial or frequency domains, followed by ‘Receptor Noise Limited Ranked Filtering’ to eliminate intermediate edge artefacts and recover sharp boundaries following smoothing. We also present a new type of colour pattern analysis, the ‘local edge intensity analysis’ as well as a range of novel psycho‐physiological approaches to the visualization of spatio‐chromatic data. QCPA combines novel and existing pattern analysis frameworks into what we hope is a unified, free and open source toolbox and introduces a range of novel analytical and data‐visualization approaches. These analyses and tools have been seamlessly integrated into the MICA toolbox providing a dynamic and user‐friendly workflow.

Colour vision testing in young children with reduced visual acuity.

To investigate feasibility, reliability and discriminative validity of pseudoisochromatic (PIC) colour vision tests, the Mollon-Reffin minimalist (MRM) test and the Cambridge Colour Test (CCT) among children (3-10years) with reduced visual acuity. Thirty-three patients with reduced visual acuity and 38 healthy control subjects with age-related normal visual acuity were recruited for this prospective study. Visual acuity in patients was reduced due to amblyopia, binocular maculopathy, or optic neuropathy. Tests were performed in a single 1-hr session. All but two children successfully completed the PIC and MRM tests. Success rate for the CCT was lower, 87%, CI [72%, 96%] for control subjects and 79%, CI [61%, 91%] for patients, with a strong positive effect of age on the odds of successful completion (OR 5.63, p=0.007). Reliability was high in PIC and MRM tests but comparably lower in CCT. The rate of correct answers in PIC tests was between 88% and 100%. One proband was diagnosed with deuteranomaly with an average Ishihara score of 21%. All children (with the exception of one daltonian) scored at least two points in the MRM test. Sensitivity thresholds in CCT decreased with age with a strong effect size in control subjects and weak to moderate effect size in patients. Pseudoisochromatic and MRM tests show sufficient feasibility in young children with reduced visual acuity. For CCT feasibility in 3-5-year olds is reduced, most probably due to the longer test duration. Consistent with earlier findings, colour discrimination thresholds decrease with age independent on visual acuity status.