Color-blind Subjects Research Articles

Incidence of Color Blindness among Undergraduates Students of Medical College in Pokhara

Introduction: There are many genetic disorders that are X-linked, one being the color blindness. Some individuals affected with the disorders may remain unaware till detected for a long time. There are very few reports about the incidence of the color blindness among the medical undergraduate students. Objectives: Ojective of our study was to assess the color blindness incidence, among the medical undergraduates at the Gandaki Medical College, Pokhara. Methodology: We piloted an observational cross-sectional study among the first and second year medical students (MBBS, BDS, Nursing, and paramedics) at Gandaki medical college. We finalized 300 students of both the genders based on the inclusion criteria. We performed in the natural day light, the color vision test using the Ishihara plates. We assessed incidence, the type of the color blindness and the gender distribution among the subjects. We compared the data thus obtained applying the “chi square statistical test” deliberating p<0.05 as significant. Results: We observed that all the colorblind subjects in the study were male who constituted 2% of the all the subjects. There was significant difference statistically among the types of the color blindness with majority having Deuteranomaly. Conclusions: We can conclude that incidence of the color blindness was exclusive among men in our study. Total color blindness was seen in majority of the male subjects. Screening the students will enable the unaware students of their disability and hence they can be guided to proper counseling.

English

BACKGROUND Colour vision is a function of three types of cone pigments present in the retina. Colour vision deficiency is an important disorder of vision that may pose a handicap to the performance of an affected individual. The prevalence of colour blindness varies in different geographical areas. The identification and estimation of the prevalence of colour vision deficiency in school-going children will help to educate and guide the caregivers to help the children in selecting their profession. This study was done to estimate the prevalence, sex distribution, and types of colour vision deficiency among school-going children of 5 to 15 years. METHODS A cross-sectional observational study was done among 500 students to evaluate the colour vision during the period from 1st January 2018 to 30th June 2019 at the Regional Institute of Ophthalmology, Kolkata. Ishihara’s pseudo isochromatic colour vision chart 38th edition was used to assess the school children for colour vision status. The children who were found to be colour blind were further classified into degree and types of colour vision deficiency. RESULTS A total of 500 students (250 male & 250 female) of surrounding schools, in the age group of 5 years to 15 years, were screened. 480 students (96 %) had normal colour vision while 20 (4 %) students were found to have defective colour vision. Prevalence (4 %) for colour blindness was found to be higher in males (3.6 %) than females (0.4 %). It was observed that out of 20 (4 %) colour-blind subjects 3.6 % were protanopes and 0.4 % were deuteranopes. CONCLUSIONS The present study shows the prevalence of colour blindness found to be quite low (4 %) and more common in males (3.6 %) in comparison to females (0.4 %). Protanomaly (3.6 %) was more common than deuteranomaly (0.4 %). KEYWORDS Colour Blindness, Protanomaly, Deuteranomaly, School Children

Spatial frequency selectivity of the human visual cortex estimated with pseudo-random visual evoked cortical potential (VECP)

Single-cell recordings in the primary visual cortex (V1) show neurons with spatial frequency (SF) tuning, which had different responses to chromatic and luminance stimuli. Visually evoked cortical potential (VECP) investigations have reported different spatial profiles. The current study aimed to investigate the spatial selectivity of V1 to simultaneous stimulus of chromatic and luminance contrasts. Compound stimuli temporally driven by m-sequences at 8 SFs were utilized to generate VECP records from thirty subjects (14 trichromats and 16 colorblind subjects). We extracted the second-order kernel, first and second slices (K2.1 and K2.2, respectively). Optimal SF, SF bandwidth, and high SF cut-off were estimated from the best-fitted functions to the VECP amplitude vs SF. For trichromats, K2.1 waveforms had a negative component (N1 K2.1) at 100 ms followed by a positive component (P1 K2.1). K2.2 waveforms also had a negative component (N1 K2.2) at 100 ms followed by a positive deflection (P1 K2.2). SF tuning of N1 K2.1 and N1 K2.2 had a band-pass profile, while the P1 K2.1 was low-pass tuned. P1 K2.1 optimal SF differed significantly from both other negative responses and from P1 K2.2. We found differences in the optimal SF, SF tuning and high SF cut-off among the VECP components. Dichromats had little or no response for all stimulus conditions. The absence of the responses in dichromats, the similarity between the high SF cut-off of the pseudorandom VECPs and psychophysical chromatic visual acuity, and presence of multiple SF tunings suggested that pseudorandom VECPs represented the activity of cells that responded preferentially to the chromatic component of the compound stimuli.

Segmentation image re-coloring based on k-means clustering algorithm as a tool for partial color-blind people

Color blindness is one of the eye anomalies that can not distinguish one color from another. Therefore, the information contained in the image may be lost seen by color blindness people. To reduce the possibility of sufferers losing color information contained in the image, a system was built in the form of re-coloring on images based on the ability of color blindness sufferers to distinguish colors. This ability is measured based on RGB cluster owned by different people. This research using color based segmentation in the process of re-coloring. Image Segmentation using K-means Clustering was chosen because of short processing time with optimum result. A total of 15 images without the coloring process were tested on color blind subjects. The result is that only 20% of the information can be seen by the color blind subject. The output of this study is the image that has been re-colored. The result of this research is that 53% of the images can be seen by the color-blind subject by using color-based segmentation in each image, 60% of the image can be seen by the color-blind subject by using color-based segmentation on all images, and processing time is shorter than previous research.

Visual evoked cortical potential elicited by pseudoisochromatic stimulus.

Visual evoked cortical potentials (VECPs) are useful for investigating the mechanisms and dysfunctions of color vision. Chromatic sinusoidal gratings are generally used to elicit VECPs, but they require long psychophysical measurements to match the perceptual luminance between their stripes. An alternative method is to use pseudoisochromatic stimuli, which makes use of luminance noise to mask luminance clues and force the target perception to be dependent on chromatic contrast. In this study, we compared VECPs generated by sinusoidal gratings and pseudoisochromatic gratings. Contrary to chromatic sinusoidal gratings, pseudoisochromatic stimuli do not require the use of previous methods to find the equiluminance of the stimulus. Normal trichromats were recruited to be tested with red-green chromatic sinusoidal gratings and pseudoisochromatic gratings presented by pattern onset-offset and pattern reversal modes in five spatial frequencies. In addition, we also tested four different chromatic contrast pairs in pattern onset-offset mode presentation in five trichromats and one colorblind subject (deuteranope). Pattern onset-offset VECPs elicited by sinusoidal gratings had a larger amplitude than those obtained with pseudoisochromatic stimuli, whereas pattern reversal VECPs elicited by pseudoisochromatic gratings had similar amplitudes compared to those elicited by sinusoidal gratings. We found no difference between the VECP amplitudes elicited by sinusoidal and pseudoisochromatic gratings containing different chromatic contrast. Color-blind subjects displayed absent or small responses to the stimuli. Pseudoisochromatic stimulus can be an alternative stimulus to generate VECPs dominated by the chromatic mechanism.

Impairment of acquired color vision in multiple sclerosis: an early diagnostic sign linked to the greatness of disease.

To assess the type and degree of both red-green and blue-yellow color vision deficiencies of Calabrian males affected by multiple sclerosis. Eighty Calabrian male patients were enrolled (age range 18-70years; mean age 40.6±12.4years) showing a disease duration mean of 10.6±8.2years (range=0.5-46years) coming from the Institute of Neurology, Magna Graecia University, Catanzaro. Optic neuritis present in the medical histories of the 21 patients does not influence color vision. Excluding seven colorblind subjects and one affected by a bilateral maculopathy, the analyzed sample group was 72. Seventy controls were matched for age and sex. An ophthalmologist examined all patients and controls in order to rule out diabetic retinopathy, cataracts, senile maculopathy, or ocular fundus' anomalies. The Ishihara test identified the colorblind patients. The City University Test screened for people with abnormal color vision by grading the severity of color vision deficiency. The second part of the City University Test as well as the Farnsworth Test confirmed both the color vision deficiency type and degree. Fifty-one percentage (37/72) of the patients showing a color vision deficiency were subdivided into two subgroups: subgroup one showed red-green deficiency (57%, 21/37); subgroup two showed a coupled red-green and blue-yellow deficiency (43%, 16/37). Furthermore, we found two distinct curves showing a groove within the first 10years of the disease. Both monocular and binocular analyses allowed us to identify the patients showing the monocular color vision deficiency, but they were well compensated by binocular vision. We think that the majority of the patients with the red-green deficiency will develop the coupled red-green and blue-yellow deficiency in the latter years of multiple sclerosis.

Low number of luminance levels in the luminance noise increases color discrimination thresholds estimated with pseudoisochromatic stimuli.

In pseudoisochromatic stimuli the presence of spatial and luminance noise forces the subject to discriminate the target from the background solely on the basis of chromaticity difference. Color-blind subjects may show difficulty to identify the target due to the elimination of borders and brightness clues caused by the luminance and spatial noise. Few studies have fully described the features of pseudoisochromatic stimuli. Fewer investigators have focused their studies in the effects of specific pseudoisochromatic parameters on color discrimination. We used the Cambridge Color Test (CCT) to investigate the influence on color discrimination thresholds due to the number of luminance levels present in the luminance noise. The CCT default has six luminance steps; however, in our investigation a total of eight different conditions were tested from 2 to 16 luminance steps. It was found that the CCT provided very robust values for color discrimination thresholds, which were degraded only for very small number of luminance steps. When the number of steps was increased, the color discrimination thresholds improved from 2 to 6 luminance steps and gradually reached a plateau for 10 or more luminance steps. The area of color discrimination ellipses as a function of luminance steps matches the relative proportion of ineffective contrasts between mosaic patches as a function of luminance steps, assuming that contrast becomes ineffective for values 18.6% or less. The lower number of color and luminance interactions in these conditions could explain the measured increase of color discrimination thresholds. The primary conclusion from this investigation was that results from pseudoisochromatic tests should have their parameters described in more detail. This type of description would allow a better understanding of the results provided, interpretations, and therefore cross study comparison of results obtained from different laboratories.

Incidence Of Color Blindness Among Some Endogamous Groups Of Bathinda District, Punjab

To find out the incidence of sex-linked defective color vision in people of Bathinda district in southern Punjab, a survey was planned among the school going boys using standard Ishihara’s Color Plates Chart. The present study was conducted on a total of 1,002 individuals belonging to 9 caste,11 backward caste and 5 scheduled caste endogamous groups, as well as a few from Muslim and Christian religious groups. In the total individuals screened as many as 34 cases of red-green color blindness and 3 of total color blindness were detected. All the red-green color blind subjects were found to be of deutan type, comprising 8 strong and 26 mild cases. No protan individual was detected in the present survey. Of the 27 endogamous groups tested, 16 groups showed absence of the trait while the incidence in remaining groups of the castes, backward castes and schedule castes were in rather similar and broad ranges between 0 to 6.7%, 0 to 6.3% and 0 to 4.7% respectively. Besides, in each of these 3 caste groupings, 1 total color blind subject was found. Compared to some initial studies on color blindness available from Punjab(average 5.2%),the present and some other recent surveys provide comparatively lower estimates of all trait (average 3.22%) which is found to be very close to that of U.P.(3.28%) and Delhi (3.15%) suggesting similarities in this genetic trait among populations of these states of the region. While in 249 populations on the North-Western Indian region so far tested the average incidence of color blindness was calculated to be 3.98%.To fully appreciate the true variation of this genetic trait and also to complete the genetic map of people of people of Punjab, further studies, are required.

This issue of Acta

This issue of Acta

Some psychological aspects of colour blindness at school: A field study in Calabria and Basilicata (Southern Italy)

AbstractRed‐green colour blindness, an inherited X‐linked anomaly, was analyzed both in its biological aspects (genetic frequency) and its pedagogical and psychological implications (only the latter are the exhaustive subject of this analysis). A mass screening was carried out by means of the Ishihara test between 1998 and 2000 in Calabria and Basilicata (South of Italy). A total of 63,933 male and female schoolchildren were investigated, belonging to 351 towns and 655 secondary schools (age range 11–14 years). Then, a psychological questionnaire was administered to the entire sample, while the psychological statistical analysis was made on the answers given by two sub‐samples composed of 34,309 orthochromatic subjects of both sexes and 831 colour‐blind subjects of both sexes. Their answers strengthen the hypothesis that dyschromatopsia could affect the human relations of its recipients starting from their childhood, forcing them to manage their diversity in order to adapt to rules, tools and didactic media and, generally, that dyschromates carry a common feeling which presupposes and takes for granted the univocality of the visual experience. Additionally, 3,082 teachers of different subjects have been submitted to a pedagogical questionnaire, consisting of 13 closed‐open questions, in order to analyze the behavior of the school toward the colour‐blind subject. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 216–220, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10148

Defective Color Perception Among Car Drivers in Addis Ababa, Ethiopia

The objective of the study was to determine the benefits of screening for color vision impairment on the ability to operate a motor vehicle safely. The study was cross-sectional in its methodology in which color vision of 1,879 randomly selected drivers was tested using Ishihare color plates. There were 85 (4.5%) cases of defective color vision. Among them, 83 (97.6%) were males and 2 (2.4%) were females. Of the 83 male cases of defective color vision, 56 (65.9%) were deuteranopes and 29 (34.1%) protanopes. The two color-blind females were deuteranopes. During the past 3 years, 27 (31.8%) color-blind subjects were reported to have had road traffic accidents compared to the total accidents of 398 (21.2%). The probability that color-blind drivers would encounter an accident was about twice as high as among non-color-blind drivers (OR = 1.94; 95% CI, 1.18-3.17; p < 0.02). We conclude that the compulsory examination of color vision in driver's license seekers in Ethiopia does not screen out color-blind individuals. Therefore, the techniques of screening should be improved either to restrict the acquisition of licenses or at least to train drivers to compensate for their defect.

Impact of color blindness on recognition of blood in body fluids.

Since color blindness is a common hereditary X-linked disorder, the authors investigated whether color blindness affects the ability to detect the presence of blood in body fluids. Ten color-blind subjects and 20 sex- and age-matched control subjects were shown 94 photographs of stool, urine, or sputum. Frank blood was present in 57 (61%) of the photographs. Surveys were done to determine if board-certified internists had ever considered whether color blindness would affect detection of blood and whether an inquiry on color blindness was included in their standard medical interview. Color-blind subjects were significantly less able to identify correctly whether pictures of body fluids showed blood compared with noncolor-blind controls (P = .001); the lowest rate of correct identifications occurred with pictures of stool. The more severely color-blind subjects were significantly less accurate than those with less severe color deficiency. Only 2 (10%) of the 21 physicians had ever considered the possibility that color blindness might affect the ability of patients to detect blood, and none routinely asked their patients about color blindness. The authors conclude that color blindness impairs recognition of blood in body fluids. Color-blind individuals and their health care providers need to be made aware of this limitation.—Thomas J. Liesegang

Impact of color blindness on recognition of blood in body fluids.

Color blindness is a common hereditary X-linked disorder. To investigate whether color blindness affects the ability to detect the presence of blood in body fluids. Ten color-blind subjects and 20 sex- and age-matched control subjects were shown 94 photographs of stool, urine, or sputum. Frank blood was present in 57 (61%) of the photographs. Surveys were done to determine if board-certified internists had ever considered whether color blindness would affect detection of blood and whether an inquiry on color blindness was included in their standard medical interview. Color-blind subjects were significantly less able to identify correctly whether pictures of body fluids showed blood compared with non-color-blind controls (P =.001); the lowest rate of correct identifications occurred with pictures of stool (median of 26 [70%] of 37 for color-blind subjects vs 36.5 [99%] of 37 for controls; P<.001). The more severely color-blind subjects were significantly less accurate than those with less severe color deficiency (P =.009). Only 2 (10%) of the 21 physicians had ever considered the possibility that color blindness might affect the ability of patients to detect blood, and none routinely asked their patients about color blindness. Color blindness impairs recognition of blood in body fluids. Color-blind individuals and their health care providers need to be made aware of this limitation.

Effect of the tuberculostaticum ethambutol and stimulus intensity on chromatic discrimination in man

In goldfish it has been shown that ethambutol shifts the threshold for wavelength discrimination without affecting the absolute sensitivity of the cones. In this study we demonstrate that a similar colour vision disturbance occurs in tuberculosis patients treated with ethambutol. After 2 months of ethambutol treatment, chromatic discrimination was measured with a computerized forced two choice (CD) test with isoluminant coloured stimuli and with three other colour vision tests: the Ishihara, the Oscar and the Lanthony Desaturated 15 Hue tests. The scores of the patient group ( n=19) on these four colour vision tests were compared with the scores of a group of control subjects ( n=33) and a group of congenital red/green colour-blind subjects ( n=5). A reduction of the stimulus intensity of 1 log unit caused a significant reduction in red/green chromatic discrimination, measured with the CD test in both, control subjects and patients. This intensity dependent reduction was significantly greater for patients than for controls. In this respect, man and goldfish behave similarly. Furthermore, the CD test showed the same ethambutol-induced reduction in chromatic discrimination at low intensity for the blue/green part of the spectrum. This has not been measured in goldfish. The origin of this ethambutol-induced colour vision disturbance must be at a post-photoreceptor site, because the Ishihara and Oscar tests, both designed to screen for photoreceptor-based, or primary red/green colour vision disturbances, did not discriminate between patients and control subjects. Thus, as in goldfish, we find that in patients ethambutol shifts the threshold for chromatic discrimination without changing the absolute sensitivity.

Tandem array of human visual pigment genes at Xq28.

Unequal crossing-over within a head-to-tail tandem array of the homologous red and green visual pigment genes has been proposed to explain the observed variation in green-pigment gene number among individuals and the prevalence of red-green fusion genes among color-blind subjects. This model was tested by probing the structure of the red and green pigment loci with long-range physical mapping techniques. The loci were found to constitute a gene array with an approximately 39-kilobase repeat length. The position of the red pigment gene at the 5' edge of the array explains its lack of variation in copy number. Restriction maps of the array in four individuals who differ in gene number are consistent with a head-to-tail configuration of the genes. These results provide physical evidence in support of the model and help to explain the high incidence of color blindness in the human population.

Color blindness and Rorschach color responsivity.

Color vision deficits occur in 10% of the American white male population. Thus, color blindness may invalidate diagnostic hypotheses generated from Rorschach data. The Rorschach protocols of 43 white, college male color-blind subjects were compared to the protocols of normally sighted controls. The color-blind group manifested fewer pure "C" responses. No significant between group differences emerged for any of the other primary Rorschach color variables. Pure "C" responses rarely figure prominently in Rorschach evaluations, and the apparent lowered frequency of these responses by the color-blind is insufficient to warrant modification of current Rorschach practice. The data suggest that color blindness is unlikely to confound Rorschach assessment.

Frequency of red/green colour blindness in twenty-seven Hungarian populations

Red/green colour blindness was examined in 40,745 individuals who participated in aptitude tests between 1976 and 1979. The screening of colour-blind subjects was performed with Ishihara plates, and further examination with anomaloscopy. The sample consisted of 33,876 males and 6896 females, all of them inhabitants of Hajdu-Bihar County. The results relative to the male subjects were anamnestically arranged according to their provenience. The sample size varies between 5·7% and 41% of the total population. The population genetic analysis shows that there are significant differences between the population samples. The total average frequency of colour blindness is 3·82 in males and 0·42% in females. The difference between expected and actual protan and deutan values is not significant. The frequencies obtained are suitable for the representation on a nationwide scale.

Performance of genetically-colorblind individuals on a rapid dark adaptation test based on the Purkinje shift.

An experiment was conducted to determine whether or not genetic colorblindness would limit performance on a rapid dark adaptation test (RDAT) which is based on the Purkinje shift in retinal sensitivity to lower wavelengths of light energy under mesopic/scotopic conditions of illumination. No differences in RDAT performance between age-equivalent colorblind and non-colorblind subjects was observed.

Color Blindness, Perceptual Interference, and Hypnosis

Abstract Forty-eight hypnotizable subjects, all capable of achieving the criterion of amnesia for a five-digit number, were divided into three groups: hypnosis, pretend-hypnosis, and waking. On the color-naming section of the Stroop Color and Word Test, the distribution of correct responses for color-blind performance of these groups was compared with the theoretical chance distribution of correct responses expected of truly color-blind subjects. The hypnosis group differed significantly from the theoretical distribution, while the pretend group did not differ significantly from the chance distribution. On the interference section of the Stroop, the number of correct responses did not differ significantly between groups.

Dermatoglyphics in Color Blindness

In four families of color blind subjects, a dermatoglyphic analysis was made and the results compared with data from normal subjects. The Student's t test, howeverf failed to show any significant differences in the means of the two groups.