A Fuzzy logic-based approach for colour vision deficiency diagnosis

Color vision research is not new for the Federal Aviation Administration (FAA); the Civil Aerospace Medical Institute has been conducting color vision research and publishing the results since 1967 ( 3 ). The FAA originally initiated color vision research because of the emerging use of color coding in the airport environment and the FAA has continued a line of color vision research because of the increasing use of color coding resulting from changing technology inside the cockpit, on air traffic control displays, and in the airport environment. Color can be used to convey meaning without supplemental signage such as the ubiquitous traffic signal that alerts drivers to proceed with caution via a yellow flashing light or to stop via a red flashing light. However, that meaning is only conveyed if the driver can distinguish between the yellow and the red colors. Approximately 8 to 10% of the male population ( 5 ) has a congenital color vision deficiency and, depending upon the type and severity of that deficiency, that task of interpreting the meaning of color coding may be difficult or impossible. Consequently, the FAA has long maintained a color vision standard for aero-medical screening to ensure that pilots and air traffic controllers can perform safety-related tasks without adverse consequences. Throughout the past few years, the FAA has explored a variety of color vision tests, searching for a valid screening test that has high sensitivity and specificity, meaning the ability to detect the presence or absence of the deficiency, respectively. Basically, color vision tests can be categorized as diagnostic, screening, or occupational tests. Diagnostic tests are designed to specifically diagnose the type and degree of deficiency, the screening tests focus on differentiating between normal or deficient color vision, and the occupational tests seek to separate those capable versus incapable of certain tasks such as identifying colors of wires or lights (e.g., the Farnsworth Lantern test that was developed to assess the ability of potential Navy signalmen for identifying red, green, and white lights). A few tests have been developed for the purpose of precisely diagnosing and classifying color vision; however, when color vision test scores are compared to performance on occupational tasks such as identifying or discriminating colors used in signal lights, precision approach path indicator (PAPI) lights, colored navigation lights, color coded map reading tasks, color coded air traffic control displays, and cockpit displays, a specific cut-point on those selection tests has not been found that can fully separate those who can from those who cannot accurately perform the color-coded pilot or air traffic control tasks. Some tests, including new computerized instruments, have been designed to differentiate defects involving the long wavelength sensitive cones (protan-type), middle wavelength sensitive cones (deutan-type), and short wavelength sensitive cones (tritan-type). Congenital protan and deutan deficiencies are, collectively, extremely common, affecting 1 in 12 men and 1 in 230 women; however, recent evidence indicates that tritan defects are virtually never present at birth (e.g., congenital) and the inherited forms involve S cone photoreceptor degeneration that develops later in life with the exact onset depending upon the specific mutation ( 1, 4 ). Thus, the exact frequency of inherited tritan defects is uncertain; however, it is probably less than 1 in 500. In part, because the underlying pathophysiology has not been well understood, few tests have been available that are capable of detecting tritan deficiencies. In the past, those tests included the single Farnsworth F2 pseudoisochromatic plate (PIP), the Moreland anomaloscope, the Hardy, Rand, Rittler PIP test, and, most recently, the Oculus anomaloscope. Consequently, the occupational color vision tests used by most agencies only screen for the most common (protan and deutan) types of defects. The newly developed computerized color vision tests, including the Colour Assessment and Diagnostic Test, the Cambridge Colour Test, the Cone Contrast Test, and the Computerized Color Vision Test, are all designed to detect tritan defects. However, tritan weaknesses have been noted in several of the FAA ‘ s recent studies in much higher than the traditionally expected numbers and diagnostic agreement is low among those tests when tritan deficiencies are involved. In the past, the FAA and other regulatory organizations have not, or have rarely, required tritan color vision screening in their occupational screening because of the following three factors: the rarity of the congenital defect, the unknown number of individuals affected by acquired deficiencies, and the lack of effective, reliable, valid, and affordable equipment with which to diagnose the deficiency.

Purpose: To investigate the type and severity of acquired colour vision deficiencies (CVDs) in molecularly proven Stargardt disease (STD) and to establish whether a relationship exists between best-corrected visual acuity (BCVA) and full-field electroretinography (ffERG), and the degree of CVD. Methods: A retrospective, cross-sectional study of 73 patients with a molecularly proven diagnosis of STD, who underwent extensive colour vision evaluation, using pseudo-isochromatic and arrangement tests. Thirteen patients underwent Nagel anomaloscopy. Results: Normal colour vision was found in almost 20% of patients. Red/green (R/G) CVDs increased as BCVA declined. About 45% of all R/G CVDs were of the deutan type, although protan type CVDs became progressively apparent when moving from the high to the low BCVA group. An additional blue/yellow CVD was noted in about 25% of patients. In 10/13 patients, a pseudoprotanomaly was noted on anomaloscopy. Severe CVDs leading to scotopization were noted in patients with low BCVA and/or long-standing disease. No statistically significant differences in ERG results were found between groups with or without a CVD. Conclusions: The degree and type of colour vision deficiency in STD patients correlate better with BCVA than with ffERG results. The presence of specific CVDs may help to establish a diagnosis of STD. A battery of colour vision tests is required to properly evaluate CVDs in STD.

Red-green colour vision deficiency (CVD) affects ~ 4% of Caucasians. Notch filters exist to simulate CVD when worn by colour vision normal (CVN) observers (simulation tools), or to improve colour discrimination when worn by CVD observers (compensation tools). The current study assesses effects of simulation (Variantor) and compensation (EnChroma) filters on performance in a variety of tasks. Experiments were conducted on 20 CVN and 16 CVD participants under no-filter and filter conditions (5 CVN used Variantor; 15 CVN and 16 CVD used EnChroma). Participants were tested on Ishihara and Farnsworth-Munsell 100 hue tests, CVA-UMinho colour discrimination and colour naming tasks and a board-game colour-sorting task. Repeated-measures ANOVAs found Variantor filters to significantly worsen CVN performance, mimicking protanopia. Mixed-model and repeated-measures ANOVAs demonstrate that EnChroma filters do not significantly enhance performance in CVD observers. Key EnChroma results were replicated in 8 CVD children (Ishihara test) and a sub-sample of 6 CVD adults (CVA-UMinho colour discrimination and colour naming tasks) for a smaller stimulus size. Pattern similarity exists across hue for discrimination thresholds and naming errors. Variantor filters are effective at mimicking congenital colour vision defects in CVN observers for all tasks, however EnChroma filters do not significantly compensate for CVD in any.

Hahn's New Pseudoisochromatic Colour Vision Test contains provision for screening red-green and blue-yellow colour vision deficiencies, a qualitative diagnosis as protan and deutan, and a quantitative diagnosis of red-green deficiencies. In this study 58 colour vision deficient and 68 colour vision normal subjects were examined using a battery of colour vision tests. The screening and classification ability of the Hahn test was compared with Ishihara's Test and the Standard Pseudoisochromatic Plates (SPP). The quantitative diagnosis ability was assessed by comparison with the Farnsworth—Munsell D-15 Test, the Farnsworth Lantern, and the Anomaloscope range. The Hahn proved to have a colour vision screening performance comparable with the two other PIC tests. Its classification ability was poor compared with the other PIC tests, one design in the SPP plates was markedly superior. The Hahn's quantitative diagnosis plates did not produce a useful classification; more than 50% of subjects made the full six errors and only 3 of 58 colour vision deficient subjects made less than 3 errors out of the 6 plates. The colorimetric measurements are used to illustrate the design features and are consistent with these performances. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 69–77 1998

Color vision tests use estimative of threshold color discrimination or number of correct responses to evaluate performance in chromatic discrimination tasks. Both approaches have advantages and disadvantages. In the present investigation, we compared the number of errors during color discrimination task in normal trichromats and participants with color vision deficiency (CVD) using pseudoisochromatic stimuli at fixed saturation levels. We recruited 28 normal trichromats and eight participants with CVD. Cambridge Color Test was used to categorize their color vision phenotype, and those with a phenotype suggestive of color vision deficiency had their L- and M-opsin genes genotyped. Pseudoisochromatic stimuli were shown with target chromaticity in 20 vectors radiating from the background chromaticity and saturation of 0.06, 0.04, 0.03, 0.02, 0.01, and 0.005 u’v' units. Each stimulus condition appeared in four trials. The number of errors for each stimulus condition was considered an indicator of the participant's performance. At high chromatic saturation, there were fewer errors from both phenotypes. The errors of the normal trichromats had no systematic variation for high saturated stimuli, but below 0.02 u’v' units, there was a discrete prevalence of tritan errors. For participants with CVD, the errors happened mainly in red-green chromatic vectors. A three-way ANOVA showed that all factors (color vision phenotype, stimulus saturation, and chromatic vector) had statistically significant effects on the number of errors and that stimulus saturation was the most important main effect. ROC analysis indicated that the performance of the fixed saturation levels to identify CVD was better between 0.02 and 0.06 u’v’ units reaching 100%, while saturation of 0.01 and 0.005 u’v’ units decreased the accuracy of the screening of the test. We concluded that the color discrimination task using high saturated stimuli separated normal trichromats and participants with red-green color vision deficiencies with high performance, which can be considered a promising method for new color vision tests based in frequency of errors.

BackgroundNeural compensatory mechanisms have been proposed, which preserve the binocular visual field in glaucoma, as well as cognition in Alzheimer's disease and motor function in Parkinson's disease. It is conceivable that comparable mechanisms operate to preserve function in congenital and/or dystrophic disease. In hereditary colour vision deficiency (CVD), we observed significant facilitation in the amplitude of the binocular cone‐specific visual evoked potential (VEP) compared to the monocular amplitude for the cone type corresponding to the CVD. We propose that this finding may reflect preservation of function in hereditary colour vision deficiency.MethodsBinocular and monocular L, M and S cone‐specific VEPs were recorded from 12 colour vision deficient subjects and 17 with normal colour vision, confirmed to be CVD or normal on a battery of colour vision tests. Binocular VEP amplitudes were compared to monocular amplitudes within subjects and between subject groups.ResultsSubjects with CVDs showed binocular facilitation of VEP amplitude (enhancement more than 2.0 times; mean: 2.8 times, p = 0.0003) for the cone type corresponding to their CVD. Mean facilitation of 2.8 times exceeded binocular enhancement for other cone types within CVDs (2.8 times versus 1.2 times) and compared to colour vision normals (2.8 times versus 1.2 times).ConclusionsHereditary CVDs show binocular facilitation of cone VEP signals for the cone type corresponding to their CVD. As CVD is typically assessed with foveal stimuli, our findings using wider‐field binocular stimulation suggest that enhanced colour perception may occur in CVD across a more extensive area of visual field. These results may relate to binocular visual field enhancement in glaucoma and improved colour vision in CVD at supra‐threshold levels of stimulation.

Purpose:To investigate the quality of life (QoL) in a sample of color vision deficit (CVD) patients in India and how color vision deficiency affects them psychologically, economically, and in productivity related to their work and occupation.Methods:A descriptive and case–control study design using a questionnaire was conducted on N = 120 participants, of whom 60 were patients of CVD (52 male and eight female) who visited two eye facilities in Hyderabad between 2020 and 2021 and 60 were age-matched normal color vision participants who served as controls. We validated English–Telugu adapted version of CVD-QoL, developed by Barry et al. in 2017 (CB-QoL). The CVD-QoL consists of 27 Likert-scale items with factors (lifestyle, emotions, and work). Color vision was assessed using the Ishihara and Cambridge Mollen color vision tests. A six-point Likert scale was used, with lower scores indicating poor QoL (from 1 = severe issue to 6 = no problem).Results:The CVD-QoL questionnaire’s reliability and internal consistency were measured, including Cronbach’s α (α =0.70–0.90). There was no significance between the group in age (t = −1.2, P = 0.67) whereas the Ishihara colour vision test, scores showed a significant difference (t = 4.50, P < 0.001). The QoL scores showed a significant difference towards lifestyle, emotions and work (P = 0.001). The CVD group had a poorer QoL score than the normal color vision group odds ratio [OR] =0.31, 95% confidence interval [CI], (P = 0.002, CI = 0.14–0.65, Z = 3.0) . In this analysis, a low CI indicated that the OR was more precise.Conclusion:Color vision deficiency affects Indians’ QoL, according to this study. The mean scores of lifestyle, emotions, and work were lower than the UK sample.Since CVD is underreported and possibly affects developing countries more, advocacy for a new health care plan on CVD is essential. Increasing public understanding and awareness could also help diagnosing the CVD population.

Background: Colour vision is the function of three types of cone pigments present in the retina. Though colours are used for important signs in the medical profession, screening for colour blindness is not paid attention at beginning of a medical career. This study was aimed to assess the presence of colour blindness, if any among the medical students of Chitwan Medical College. Methods: A total of 220 medical students including 127 females and 93 males aged between 16-24 years were examined for colour blindness. Students were shown the complete range of Ishihara’s plates under daylight conditions. The chart was held 75 cm away from the subjects. The types of colour vision deficiency were differentiated with help of key provided with the chart. The data was analyzed by using Statistical Package for the Social Sciences version 20. Results: Among 220 participants, 5(2.27%) were found to have colour vision deficiency. Out of 5colourdeficient students, 4of them were red-green colour vision deficient and 1 of them couldn’t appreciate colour (total colour blindness) within the speculated time for the test. Female partici­pants didn’t have colour vision deficiency while colour vision deficient students were unaware of their colour vision status. Conclusions: Colour vision deficiency affects male than female. Medical students should be screened for colour vision deficiency and made aware of their limitation so that they can take special care in their future clinical practice.

Introduction: Colour vision deficiency is a common but unnoticed condition. Medical students must be aware of their congenital colour vision deficiency and its effects on their work, so that color vision deficient student may not choose the discipline such as pathology and radiology, where colour vision is very important. Methods: This is a cross-sectional study conducted in the Department of Clinical Physiology, Maharajgunj Medical Campus, Institute of Medicine, Kathmandu from February 2013 to January 2016. Total of 556 medical and nursing students selected by convenient sampling, underwent color vision evaluation by using Ishihara chart. Results: Out of 302 male students, 20 (6.6%) were color vision deficient. Similarly, out of 254 female students, two (0.8%) were colour vision deficient. Among the male students, two (10%) were total colour blind, eight (40%) were suffering from deuteranomaly and 10 (50%) were suffering from deuteranopia. Colour vision deficiencies were observed more in Chhetri (9.5%), followed by Brahmin (7.1%) and Madhesi ethnicity (6.9%). Conclusion: The prevalence of colour vision deficiency in Nepalese medical students is significant. Therefore, they should be screened for colour vision deficiency, so that the students with colour vision defect can choose appropriate discipline as their future carrier where colour vision defect may not affect their work.

One of the most common inherited vision disorders is congenital color vision deficiency (CVD). Its prevalence in men can be as high as 8% and 0.5% in women.[1] Men are predominately affected by the X-linked inheritance pattern, while women become carriers of the abnormal gene.[2] There are also different causes for acquired color vision defects, such as ocular or neurological disease, some metabolic disorders, drug toxicity and exposure to certain solvents.[3] Congenital CVD results from genetic mutations that affect the expression of the full complement of normal cone photoreceptors. They’re divided into three categories based on their intensity (anomalous trichromacy, dichromacy, and monochromacy). CVD places the sufferer at a distinct disadvantage when performing certain visual tasks—in particular those tasks in which a colored target is embedded in a variegated background of a different color. CVD affects many areas of life, and its adverse impact is experienced at all stages, i.e., from childhood to adolescence and adulthood.[45] Population is one of the biggest problems in India and the reason for so many compromises starting from lack of resources at every level. Healthcare is just one example. When providing even simple vision assessment in school children becomes a big task few tests like color vision examination is rarely being performed. Population diagnosis is usually late at the time of medical examination at the time of higher education or specific job. They are rarely diagnosed early in life. Late diagnosis leads to rejection for a particular job most of the time which has a psychological impact on individuals. In India where an education system doesn’t give a student to choose multiple streams, it turns out, several professional choices can be negatively impacted by a color blindness diagnosis. CVD is a hidden disability because, though present from birth, its role comes to play only when children begin to attend regular schools to learn some tasks.[6] From here onwards process of considerable difficulties in learning starts. Children with CVD are frequently marked as lethargic students, which could mentally affect them, or could evoke negative responses from instructors and guardian. This can lead to not only problems in learning but also in playing and in their social bonding. Various studies have been carried out all over the world to see the prevalence of CVD among school children.[789] Xie JZ, et al.[10] suggested that successful CVD testing can be done starting at age four. Cole stressed that school children should know if they have CVD so they can be helped more quickly to find adaptive strategies and be able to take it into account when planning their career.[11] Largest study on CVD in children is conducted to see the burden of this disability in India.[12] Authors have used Dalton’s psuedoisochromatic plates for color vision screening. It is based on Ishihara color vision chart principle. The Dalton screener consists of 6 sets with 4 plates in each that includes one demo plate and three screening plates. Those, who failed to read three or more plates in two or more random sets of the Dalton’s pseudoisochromatic plate were considered to have CVD after confirming with Ishihara’s PIP color vision testing (38 plate edition). The result shows CVD among boys was found to be 2.76%. Children from urban region (3.17%) were more likely to be color vision deficient than children from rural region (1.79%). These results are similar to the other parts of the country and few other countries from Asia. Screening of CVD is relatively easy does not require any formal training and can be performed by any assigned staff. Various plate tests are available, such as Ishihara, Tokyo, HRR plate test, which are highly sensitive and specific to detect CVD. Because of rapidly evolving technologies with more and more use of color coded tasks in each sector including education sector and specific job requiring color differentiation, the efforts should be made at a fundamental level in screening of color vision defects during comprehensive school eye health programs. Since CVD is congenital and there is no permanent cure for it. However, advice at an early age could help to find adaptive strategies, which enable them to avoid disappointments in the choice of their future career. Parental education, awareness, genetic counseling strategies in the regions with high CVD incidence could help a lot in minimizing the occurrence of the disorder among their offspring.

PurposeNormal color vision depends on normal long wavelength (L), middle wavelength (M), and short wavelength sensitive (S) cones. Hereditary “red-green” color vision deficiency (CVD) is due to a shift in peak sensitivity or lack of L or M cones. Hereditary S cone CVD is rare but can be acquired as an early sign of disease. Current tests detect CVD but few diagnose type or severity, critical for linking performance to real-world demands. The anomaloscope and newer subjective tests quantify CVD but are not applicable to infants or cognitively impaired patients. Our purpose was to develop an objective test of CVD with sensitivity and specificity comparable to current tests.MethodsA calibrated visual-evoked potential (VEP) display and Food and Drug Administration-approved system was used to record L, M, and S cone-specific pattern-onset VEPs from 18 color vision normals (CVNs) and 13 hereditary CVDs. VEP amplitudes and latencies were compared between groups to establish VEP sensitivity and specificity.ResultsCone VEPs show 100% sensitivity for diagnosis of CVD and 94% specificity for confirming CVN. L cone (protan) CVDs showed a significant increase in L cone latency (53.1 msec, P < 0.003) and decreased amplitude (10.8 uV, P < 0.0000005) but normal M and S cone VEPs (P > 0.31). M cone (deutan) CVDs showed a significant increase in M cone latency (31.0 msec, P < 0.000004) and decreased amplitude (8.4 uV, P < 0.006) but normal L and S cone VEPs (P > 0.29).ConclusionsCone-specific VEPs offer a rapid, objective test to diagnose hereditary CVD and show potential for detecting acquired CVD in various diseases.Translational RelevanceThis paper describes the efficacy of cone-specific color VEPs for quantification of normal and abnormal color vision. The rapid, objective nature of this approach makes it suitable for detecting color sensitivity loss in infants and the cognitively impaired.

Colour vision is a complex visual function that can be affected by congenital and/or acquired disorders. The frequency of congenital colour vision deficiencies has been investigated in rail and navy staff since the 1870s. Various test methods have been developed. Wool tests, flor contrast tests and colour plate tests have been used. A published colour plate test, based on Stilling's pseudo-isochromatic plates in combination with a flor contrast test, has been a common screening method for colour vision testing in German-speaking countries. This test is intended to detect congenital and acquired colour vision deficiencies in a simple and safe manner. More modern options, such as Internet and tablet PC have technical limitations, but will increasingly be used for screening for colour vision deficiencies.

Color is an important characteristic of the aviation environment. Pilots must rapidly and accurately differentiate and identify colors. The medical standards published by the International Civil Aviation Organization (ICAO) require that pilots have "the ability to perceive readily those colors the perception of which is necessary for the safe performance of duties." The general wording of that color vision (CV) standard, coupled with the associated flexibility provisions, allows for different approaches to the assessment of color vision deficient (CVD) pilots. Data was gathered and analyzed regarding medical assessment practices applied by different countries to CVD pilots. Data was obtained from 78 countries, representing 78% of the population and 92% of the aviation activity of the world. That data indicates wide variation in the medical assessment of CVD pilots. Countries use different tools and procedures for the testing of pilots, and also apply different result criteria to those tests. At one extreme an applicant making one error upon Ishihara 24-plate pseudoisochromatic plate (PIP) testing is declined a class 1 medical assessment, while at another extreme an applicant failing every color vision test required by the regulatory authority may be issued a medical assessment allowing commercial and airline copilot privileges. The medical assessment of CVD applicants is not performed consistently across the world. Factors that favor uniformity have been inadequate to encourage countries toward consistent medical assessment outcomes. This data is not consistent with the highest practicable degree of uniformity in medical assessment outcomes, and encourages aeromedical tourism.

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.

Background: People with color vision deficiencies report numerous limitations in daily life, restricting, for example, their access to some professions. However, they use basic color terms systematically and in a similar manner as people with normal color vision. We hypothesize that a possible explanation for this discrepancy between color perception and behavioral consequences might be found in the gaze behavior of people with color vision deficiency.Methods: A group of participants with color vision deficiencies and a control group performed several search tasks in a naturalistic setting on a lawn. All participants wore a mobile eye-tracking-driven camera with a high foveal image resolution (EyeSeeCam). Search performance as well as fixations of objects of different colors were examined.Results: Search performance was similar in both groups in a color-unrelated search task as well as in a search for yellow targets. While searching for red targets, participants with color vision deficiencies exhibited a strongly degraded performance. This was closely matched by the number of fixations on red objects shown by the two groups. Importantly, once they fixated a target, participants with color vision deficiencies exhibited only few identification errors.Conclusions: In contrast to controls, participants with color vision deficiencies are not able to enhance their search for red targets on a (green) lawn by an efficient guiding mechanism. The data indicate that the impaired guiding is the main influence on search performance, while foveal identification (verification) is largely unaffected by the color vision deficiency.