Color Vision Deficiency Subjects Research Articles

CVD-MET: an image difference metric designed for analysis of color vision deficiency aids.

Color vision deficiency (CVD) has gained in relevance in the last decade, with a surge of proposals for aid systems that aim to improve the color discrimination capabilities of CVD subjects. This paper focuses on the proposal of a new metric called CVD-MET, that can evaluate the efficiency and naturalness of these systems through a set of images using a simulation of the subject's vision. In the simulation, the effect of chromatic adaptation is introduced via CIECAM02, which is relevant for the evaluation of passive aids (color filters). To demonstrate the potential of the CVD-MET, an evaluation of a representative set of passive and active aids is carried out both with conventional image quality metrics and with CVD-MET. The results suggest that the active aids (recoloration algorithms) are in general more efficient and produce more natural images, although the changes that are introduced do not shift the CVD's perception of the scene towards the normal observer's perception.

Robust categorical color constancy along daylight locus in red-green color deficiency.

Categorical color constancy in normal trichromats has been found to be very robust in real scenes. In this study, we investigated categorical color constancy in red-green dichromats and anomalous trichromats. Eight dichromats (two protanopes and six deuteranopes), eight anomalous trichromats (four protanomalous and four deuteranomalous trichromats), and eight normal trichromats sorted 208 Munsell matte surfaces into Berlin and Kay's basic color categories under D65 illuminant, F illuminant with correlated color temperature 4200 K, and TL84 illuminant with correlated color temperature 2700 K. Color constancy was quantified by a color constancy index. The results showed that the constancy index of dichromats (0.79) was considerable and significantly lower than that of normal trichromats (0.87) while that of anomalous trichromats (0.84) was not. The impairment of color constancy performance in dichromats was expected to be caused by their large intra-subject variabilities in color naming. The results indicate robust categorical color constancy along daylight locus in red-green dichromats and anomalous trichromats, which might be contributed by cone adaptation mechanism and be independent of color discrimination mechanism. It suggests that the color categorization by color vision deficient subjects can be reasonable without any assistants of artificial equipment in daily life under sunlight and common illuminations.

Prevalence of color vision deficiency and it’s relation with ABO blood group among medical students

Background: Normal human beings can appreciate color in all three of it’s attributes; Hue, intensity, and saturation. Human beings can perceive three primary colors, that is, red, green, and blue. Any defect in appreciation of colors is known as color vision deficiency (CVD). Complete inability to appreciate color is known as color blindness. The genes for red and green cone pigments are found in the q arm of the X chromosome. Hence, red and green CVD are inherited as X-linked recessive diseases. Blue CVD is autosomaly inherited. Blood groups are genetically inherited as well. Although it is a known fact that there is a preponderance of genetic diseases in subjects belonging to a specific blood group, no such study was available in Western Odisha as per our knowledge. This becomes more relevant as consanguineous marriages are a serious social problem in that part of Odisha. Aim and Objectives: Therefore, the study was undertaken to find out the prevalence of CVD among Medical students in Western Odisha and to find out it’s relation, if any, with ABO blood groups, as these two entities are genetically inherited. Record should be kept for future use, especially for counseling at the time of marriage and if necessary, to choose a subject for further study, where color detection does not play an important part. Materials and Methods: Prior permission was taken from the Institutional Ethics Committee to carry out this study. The study was carried out among the 1st–4th year medical students of V.S.S. Medical College and Hospital (n = 690) from August 2022 to October 2022. Ishihara test plates for color vision and agglutination method for ABO blood grouping were employed to get the prevalence of CVD and to get the percentage of subjects belonging to each blood group among those having CVD. The observations were noted carefully. Results: After careful screening, it was seen that 647 (93.76%) were normal, 42 (6.08%) had CVD, and 1 (0.14%) subject was completely color blind. All those affected were males. Distribution of blood group in CVD subjects showed 7 (16.27%) numbers belonging to blood group A, 22 (51.16%) belonging to blood group B, 1 (2.3%) belonging to blood group AB, and 12 (27.9%) belonging to blood group O. The only color blind student belonged to blood group B (2.3%). Conclusion: As medical students have to deal with colors throughout their career, the study helps the subjects to be aware of their condition early in their professional life. It also tried to find out the percentage distribution into ABO blood groups. A larger population should be included to get more accurate results.

Effects of Intermediate-Tinted Lenses on Pistol Marksmanship and Visual Performance.

The standard issue clear or sun Military Combat Eye Protection (MCEP) is often inadequate in visually challenging training or combat environment. Intermediate-tinted lenses may offer a viable option for warfighters operating in dynamic visual conditions such as moving rapidly from bright sunny areas to darker building interiors in combat. Because the use of intermediate-tinted lenses has been delayed as a result of a potential negative impact on vision performance such as color perception, this investigation evaluated several commercially available intermediate-tinted lenses for operation performance during a U.S. military field training. Test lenses complied with all the requirements of the current MCEP except for the visible light transmittance (VLT) values that ranged between 32 and 62%. Study subjects consisted of 22 service members who attended a military Close Combat and Marksmanship training course in May 2019. Visual and pistol marksmanship performance of three intermediate-tinted lenses (Eye Safety Systems [ESS] Copper [32% VLT], Oakley Prizm TR45 [44% VLT], and ESS Bronze [62% VLT]) was compared to that of a standard issue MCEP, ESS Clear (90% VLT). Quick contrast sensitivity function test was used to assess quality vision (AULCSF, area under a log contrast sensitivity function) and visual acuity (CSF Acuity). Color vision was assessed by Cone Contrast Test. Pistol marksmanship (Bill Drill) was used for performance testing. A pre-survey inquired about MCEP use, and a MCEP survey during the pistol marksmanship testing inquired about lens performance and ranking. AULCSF and CSF Acuity were significantly affected by the lenses (general linear model, repeated measures, P < .05). Bonferroni post hoc test showed a significant reduction of binocular AULCSF from ESS Clear to Oakley Prizm TR45 (P = .003) and ESS Copper (P < .001) and a significant reduction in binocular CSF Acuity from ESS Clear to ESS Copper (P = .001). Color vision and pistol marksmanship performance were not significantly affected by wearing different lenses (P > .05). Subjectively, there were no statistically significant differences among study lenses in perceived "clarity of vision," "ability to clearly identify the target," or "overall performance" (Friedman test and Wilcoxon signed-rank post hoc test with Bonferroni adjustment, P > .017). Participants ranked Prizm TR45 (44% VLT) and ESS Bronze (62% VLT) lenses significantly more favorably than EES Clear (P = .001 and P = .009). Quality of vision and visual acuity decreased with darker lenses; however, the study lenses had insignificant impacts on pistol marksmanship and subjective acceptance. Our surveys indicated that Intermediate-tinted lenses were operationally acceptable and preferred over a standard issue MCEP. While more evaluations for color vision deficient subjects are needed, overall results suggest that commercially available intermediate-tinted lenses may be a viable option to enhance protection and performance in a visually dynamic combat environment.

Spectral Filter Selection for Increasing Chromatic Diversity in CVD Subjects.

This paper analyzes, through computational simulations, which spectral filters increase the number of discernible colors (NODC) of subjects with normal color vision, as well as red–green anomalous trichromats and dichromats. The filters are selected from a set of filters in which we have modeled spectral transmittances. With the selected filters we have carried out simulations performed using the spectral reflectances captured either by a hyperspectral camera or by a spectrometer. We have also studied the effects of these filters on color coordinates. Finally, we have simulated the results of two widely used color blindness tests: Ishihara and Farnsworth–Munsell 100 Hue (FM100). In these analyses the selected filters are compared with the commercial filters from EnChroma and VINO companies. The results show that the increase in NODC with the selected filters is not relevant. The simulation results show that none of these chosen filters help color vision deficiency (CVD) subjects to pass the set of color blindness tests studied. These results obtained using standard colorimetry support the hypothesis that the use of color filters does not cause CVDs to have a perception similar to that of a normal observer.

Limitations and Precautions in the Use of the Farnsworth-Munsell Dichotomous D-15 Test

Clinicians who administer the Farnsworth-Munsell D-15 test need to pay attention to the quality and quantity of lighting and the time that they allow for completion of the test, and all repeat attempts need to be included in reports on compliance with color vision standards. The validity of the Farnsworth-Munsell D-15 has been questioned because practice may allow significantly color vision-deficient subjects to pass. In this article, we review the influence of practice and other factors that may affect the performance. These relate to both the design and the administration of the test. We review the literature and present some calculations on limitations in the colorimetric design of the test, quantity and quality of lighting, time taken, and repeat attempts. In addition to the review of the literature, color differences and luminance differences under selected sources are calculated, and the increases in luminance clues under some sources and for protanopes are illustrated. All these factors affect the outcome of the test and need specification and implementation if the test is to be applied consistently and equitably. We recommend the following: practitioners should never rely on a single color vision test regardless of the color vision standard; lighting should be Tcp '' 6500 K and Ra > 90; illuminance levels should be between 200 and 300 lux if detection of color vision deficiency is a priority or between 300 and 1000 lux if the need is to test at the level where illuminance has minimal influence on performance; illuminance should be reported; time limits should be set between 1 and 2 minutes; repeat testing (beyond the specified test and one retest) should be carried out only with authorization; and initial and repeated results should be reported. A set of test instructions to assist in the consistent application of the test is provided in the Appendix.

Assessment of VINO filters for correcting red-green Color Vision Deficiency.

In our ongoing research on the effectiveness of different passive tools for aiding Color Vision Deficiency (CVD) subjects, we have analyzed the VINO 02 Amp Oxy-Iso glasses using two strategies: 1) 52 observers were studied using four color tests (recognition, arrangement, discrimination, and color-naming); 2) the spectral transmittance of the lenses were used to model the color appearance of natural scenes for different simulated CVD subjects. We have also compared VINO and EnChroma glasses. The spectral transmission of the VINO glasses significantly changed color appearance. This change would allow some CVD subjects, above all the deutan ones, to be able to pass recognition tests but not the arrangement tests. To sum up, our results support the hypothesis that glasses with filters are unable to effectively resolve the problems related to color vision deficiency.

Discrimination of colors by red-green color vision-deficient observers through digitally generated red filter.

Previous studies have shown that with the use of tinted lenses (or colored filters), individuals with red-green color vision deficiency (CVD) report an improvement in their performance on certain color vision tests. In this context, this study examines the effects of a digitally generated red-colored filter and identifies the mechanism mainly responsible for the changes in red-green CVD observers' performance on a D-15 arrangement test performed using the filter. We simulate the red filter digitally with the spectral transmittance similar to that of the X-Chrom, which is a red-tinted lens. Fourteen red-green CVD subjects are subjected to the D-15 test on a computer monitor under four filter conditions, consisting of one condition without the filter and three conditions with the filter, corresponding to the opacity of the red filter. The results show that while the simulated red filter improves the performance of deutans to arrange the caps in the D-15 test, this is not the case for protans. In addition, considerations based on the human cone-contrast model enable us to identify that the improvement in deutan observers largely results from the increase in the luminance contrast between stimuli and a background. To summarize, the red filter simulated in this study induces different changes in the red-green CVD observer luminance contrast between the protan and deutan types, with the result that the performance of deuteranopes improves while that of protanopes deteriorates.

Validity and Acceptance of Color Vision Testing on Smartphones.

Ishihara color plates (ICP) are the most commonly used color vision test (CVT) worldwide. With the advent of new technologies, attempts have been made to streamline the process of CVT. As hardware and software evolve, smartphone-based testing modalities may aid ophthalmologists in performing more efficient ophthalmic examinations. We assess the validity of smartphone color vision testing (CVT) by comparing results using the Eye Handbook (EHB) CVT application with standard Ishihara color plates (ICP). Prospective case-control study of subjects 18 years and older with visual acuity of 20/100 or better at 14 inches. The study group included patients with any ocular pathology. The color vision deficient (CVD) group was patients who failed more than 2 plates. The control group had no known ocular pathology. CVT was performed with both ICP and EHB under standardized background illuminance. Eleven plates were tested with each modality. Validity of EHB CVT and acceptance of EHB CVT were analyzed. Statistical analyses were performed using Bland-Altman plot with limits of agreement (LOA) at the 95th percentile of differences in score, independent samples t tests with 95% confidence interval (CI), and Pearson χ tests. The Bland-Altman plot showed agreement between correct number of plates in EHB and ICP for the study subjects (bias, -0.25; LOA, -1.92 to 1.42). Agreement was also observed between the correct number of plates in EHB and ICP for the controls (bias, -0.01; LOA, -0.61 to 0.59) and CVD (bias, -0.50; LOA, -4.64 to 3.64) subjects. The sensitivity of EHB was 0.92 (95% CI 0.76-1.07) and the specificity of EHB was 1.00 (95% CI 1.00-1.00). Fifty-nine percent preferred EHB, 12% preferred ICP, and 29% had no preference. In healthy controls and patients with ocular pathology, there was an agreement of CVT results comparing EHB with ICP. Overall, the majority preferred EHB to ICP. These findings demonstrate that further testing is required to understand and improve the validity of smartphone CVT in subjects with ocular pathology.

Reduced Discrimination in the Tritanopic Confusion Line for Congenital Color Deficiency Adults.

In congenital color blindness the red–green discrimination is impaired resulting in an increased confusion between those colors with yellow. Our post-receptoral physiological mechanisms are organized in two pathways for color perception, a red–green (protanopic and deuteranopic) and a blue–yellow (tritanopic). We argue that the discrimination losses in the yellow area in congenital color vision deficiency subjects could generate a subtle loss of discriminability in the tritanopic channel considering discrepancies with yellow perception. We measured color discrimination thresholds for blue and yellow of tritanopic channel in congenital color deficiency subjects. Chromaticity thresholds were measured around a white background (0.1977 u′, 0.4689 v′ in the CIE 1976) consisting of a blue–white and white–yellow thresholds in a tritanopic color confusion line of 21 congenital colorblindness subjects (mean age = 27.7; SD = 5.6 years; 14 deuteranomalous and 7 protanomalous) and of 82 (mean age = 25.1; SD = 3.7 years) normal color vision subjects. Significant increase in the whole tritanopic axis was found for both deuteranomalous and protanomalous subjects compared to controls for the blue–white (F2,100 = 18.80; p < 0.0001) and white–yellow (F2,100 = 22.10; p < 0.0001) thresholds. A Principal Component Analysis (PCA) found a weighting toward to the yellow thresholds induced by deuteranomalous subjects. In conclusion, the discrimination in the tritanopic color confusion axis is significantly reduced in congenital color vision deficiency compared to normal subjects. Since yellow discrimination was impaired the balance of the blue–yellow channels is impaired justifying the increased thresholds found for blue–white discrimination. The weighting toward the yellow region of the color space with the deuteranomalous contributing to that perceptual distortion is discussed in terms of physiological mechanisms.

Color Vision and the Railways: Part 1. The Railway LED Lantern Test.

Lantern tests and practical tests are often used in the assessment of prospective railway employees. The lantern tests rarely embody the actual colors used in signaling on the railways. Practical tests have a number of problems, most notably consistency of application and practicability. This work was carried out to provide the Railway LED Lantern Test (RLLT) as a validated method of assessing the color vision of railway workers. The RLLT, a simulated practical test using the same LEDs (light-emitting diodes) as are used in modern railway signals, was developed. It was tested on 46 color vision-normal (CVN) and 37 color vision-deficient (CVD) subjects. A modified prototype was then tested on 106 CVN subjects. All 106 CVN subjects and most mildly affected CVD subjects passed the modified lantern at 3 m. At 6 m, 1 of the 106 normal color vision subjects failed by missing a single red light. All the CVD subjects failed. The RLLT carried out at 3 m allowed mildly affected CVD subjects to pass and demonstrate adequate color vision for the less demanding railway tasks. Carried out at 6 m, it essentially reinforced normal color vision as the standard. The RLLT is a simply administered test that has a direct link to the actual visual task of the rail worker. The RLLT lantern has been adopted as an approved test in the Australian National Standard for Health Assessment of Rail Safety Workers in place of a practical test. It has the potential to be a valid part of any railway color vision standard.

Prevalence of Color Vision Deficiency and its Correlation with Amblyopia and Refractive Errors among Primary School Children.

Purpose:To determine the prevalence of color vision deficiency (CVD) and its correlation with amblyopia and refractive errors among primary school children.Methods:In this population-based cross-sectional study, 2160 children were selected from 36 primary schools; 60 students were from each school (10 students in each grade), with equal sex distribution. A complete eye examination including refraction using a photorefractometer, determination of visual acuity (VA) and color vision using a Yang vision tester, and evaluation of ocular media opacity using a direct ophthalmoscope was performed. Children who could not answer at least 4 plates of the Ishihara color test were considered as color vision deficient subjects. Amblyopia was determined if pinhole VA was worse than 0.3 LogMAR (equal to 20/40).Results:The prevalence of CVD was 2.2% (95% CI: 1.5% to 3%) which was higher in male subjects (37 [3.5%] boys vs. 11 [1.0%] girls, P < 0.001). Mean VA was lower among students with CVD as compared to normal color vision children (P = 0.035) and amblyopia was observed in 8.3% (95% CI: 0.2% to 16.4%) of patients with CVD versus 2.1% (95% CI: 1.5% to 2.08%) of children with normal color vision perception (P = 0.005). A statistically significant correlation between lower VA and CVD was observed (P = 0.023).Conclusion:Although CVD was correlated with lower VA and amblyopia, there was no relationship between CVD and the type of amblyopia, refractive error, anisometropia or strabismus.

Prevalence of refractive error in school childrens with color vision deficiencies

AbstractPurpose To assess the refractive error status in subjects with color vision deficiency (CVD) and color normal (CN) in order to make a contribution to a better understanding of emmetropization process.Methods A total of 4400 students were screened using a Ishihara pseudoisochromatic color vision plate set. One hundred and sixty students were detected to have CVD. Four hundred age and sex match were set as the control group. Objective refraction was performed to determine the refractive status of the subjects.Results The prevalence of myopia in CVD group was 7.7% that was significantly lower than CN subjects (13.9%). Furthermore, CVD group presented with lower prevalence of hyperopia (41%) in comparison with CN group (57.4%). In addition, CVD subjects were presented with lower magnitude of refractive error in comparison with NC.Conclusion Although lower prevalence of myopia support the theory of the role of Longitudinal chromatic aberration in refractive error development, lower prevalence of hyperopia in CVD group is in contrary with that. This Results indicated that longitudinal chromatic aberration is not the only factor that could influences the emmetropization process.

Prevalence of Refractive Errors in Students with and without Color Vision Deficiency.

Purpose:To evaluate refractive errors in school age children with color vision deficiency (CVD) and those with normal color vision (NCV) in order to make a better understanding of the emmetropization process.Methods:A total of 4,400 primary school students aged 7–12 years were screened for color vision using Ishihara pseudoisochromatic color vision plate sets. Of these, 160 (3.6%) students had CVD. A total of 400 age- and sex-matched students with NCV were selected as controls. Refractive status was evaluated using objective cyclorefraction.Results:The CVD group included 136 male (85%) and 24 female (15%) subjects with mean age of 10.1 ± 1.8 years. The NCV group comprised of 336 male (84%) and 64 female (16%) subjects with mean age of 10.5 ± 1.2 years. The prevalence of myopia (7.7% vs. 13.9%, P < 0.001) and hyperopia (41% vs. 57.4%, P = 0.03) was significantly lower in the CVD group. Furthermore, subjects with CVD subjects demonstrated a lower magnitude of refractive errors as compared to the CVD group (mean refractive error: +0.54 ± 0.19 D versus + 0.74 ± 1.12 D, P < 0.001).Conclusion:Although the lower prevalence of myopia in subjects with CVD group supports the role of longitudinal chromatic aberration in the development of refractive errors; the lower prevalence of hyperopia in this group is an opposing finding. Myopia is a multifactorial disorder and longitudinal chromatic aberration is not the only factor influencing the emmetropization process.

Categorical Color Naming of Surface Color Codes by People With Abnormal Color Vision

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. 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. 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. 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).

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.

Melatonin regulation in humans with color vision deficiencies.

Light can induce an acute suppression and/or circadian phase shift of plasma melatonin levels in subjects with normal color vision. It is not known whether this photic suppression requires an integrated response from all photoreceptors or from a specialized subset of photoreceptors. To determine whether normal cone photoreceptor systems are necessary for light-induced melatonin suppression, we tested whether color vision-dificient human subjects experience light-induced melatonin suppression. In 1 study, 14 red-green color vision-deficient subjects and 7 normal controls were exposed to a 90-min, 200-lux, white light stimulus from 0200-0330 h. Melatonin suppression was observed in the controls (t = -7.04; P < 0.001), all color vision-deficient subjects (t = -4.76; P < 0.001), protanopic observers (t = -6.23; P < 0.005), and deuteranopic observers (t = -3.48; P < 0.05), with no significant difference in the magnitude of suppression between groups. In a second study, 6 red/green color vision-deficient males and 6 controls were exposed to a broad band green light stimulus (120 nm with lambda max 507 nm; mean +/- SEM, 305 +/- 10 lux) or darkness from 0030-0100 h. Hourly melatonin profiles (2000-1000 h) were not significantly different in onset, offset, or duration between the two groups. Melatonin suppression was also observed after exposure to the green light source at 0100 h (color vision deficient: t = -2.3; df = 5; P < 0.05; controls: t = -3.61; df = 5; P < 0.01) and 0115 h (color vision deficient: t = -2.74; df = 5; P < 0.05; controls: t = -3.57; df = 5; P < 0.01). These findings suggest that a normal trichromatic visual system is not necessary for light-mediated neuroendocrine regulation.