Color Deficiency Research Articles

What limits chromatic sensitivity in normal and colour deficient observers?

Abstract Purpose Variability in chromatic sensitivity was assessed in normal trichromats (n=133) and in subjects with deutan (n= 106) and protan (n=48) deficiency. The purpose of this study was to quantify variability within normal colour vision and to determine how this impacts the assessment of minimum colour vision requirements within occupational environments. Methods Rayleigh matches were modelled with the aim of explaining the locations of match midpoints and ranges. Model parameters included the wavelength of peak sensitivity of cone photopigments, the photopigment optical density and the noise amplitude in the red/green colour channel. In order to avoid the suprathreshold, perceptual effects of extreme L:M cone ratios on colour vision, selective postreceptoral amplification of cone signals is needed. The noise is also amplified and this causes corresponding changes in red/green threshold sensitivity. Results We measured midpoint and matching range in anomaloscope matches and red/green and yellow/blue thresholds under conditions that isolate the use of colour signals. A subset of subjects with deutan deficiency that exhibited less common Nagel matches were selected for genetic analysis of their cone pigment genes to predict the corresponding peak wavelength separation of their two, long‐wavelength cone pigments. Conclusion The model predicts accurately the midpoint and the range for the spectral differences specified by the genes. The model also predicts the “normal” matches made by some subjects that rely on two hybrid genes and therefore exhibit red/green thresholds outside the normal range, typical of mild deuteranomaly. The anomaloscope is therefore not by itself sufficient to classify with certainty the colour deficiency involved.

Chromatic VEP in colour deficient children

Abstract Purpose To compare chromatic VEP response to isoluminant red‐green stimulus in children with congenital red‐green colour deficiency with a control group of 30 children with normal colour vision. Methods 15 children (7‐18 years) with congenital colour vision deficiency (8 in deutan and 7 in protan axis) and 30 healthy children (7‐19 years) were included in the study. Colour vision was assessed with Ishihara plates, Nagel Anomaloscope, Mollon‐Reffin Minimalist test, Farnsworth‐Munsell D‐15 saturated and desaturated test and Farnsworth‐Munsell hue 100 test. VEP were recorded to isoluminant red‐green stimulus. The stimulus was a 7 deg large circle composed of horizontal sinusoidal gratings, with spatial frequency 2 cycles/deg and 90 % chromatic contrast. VEP were recorded from Oz (mid occipital) position. Children were tested binocularly. Latency and amplitude of positive (P) and negative (N) wave were measured and so was mean amplitude (N‐P wave). Results N wave was present in 24/30 children with normal colour vision (110 ± 25.1 ms; 9.7 ± 4.8 μV) and only in 1/15 child with colour vision deficiency (93 ms; 3.2 μV). P wave was present in 30/30 children with normal colour vision (138 ± 21.1 ms; 21.1 ± 13.5 μV) and in 13/15 children with colour vision deficiency (131.9 ± 6.1 ms; 19.4 ± 10.7 μV). In healthy children waveform changed from predominantly positive to negative wave with increasing age, whereas in colour deficient children no obvious waveform changes were observed. Conclusion VEP response to isoluminant chromatic stimulus showed different characteristics in children with congenital colour vision deficiency compared to children with normal colour vision. manca.tekavcic‐pompe@guest.arnes.si

Eficiência dos testes cromáticos de comparação na discromatopsia hereditária: relato de casos

The authors describe two cases of hereditary dyschromatopsia and discuss the efficiency of the color vision tests. The patients were disapproved in different federal public examinations because Ishihara's test diagnosed hereditary dyschromatopsia. Ophthalmological evaluation was normal. No symptoms related to dyschromatopsia were presented. Panels D15 and Roth D 28 were normal. Desaturated D 15 showed deuteranomaly in case one. In the second case the comparative color vision tests showed nonspecific disorder. The diagnosis of dyschromatopsia is complex. The authors recommend comparative color vision tests to complement the Ishihara test for a better understanding of the color deficiency.

Failure of concordance of the Farnsworth D15 test and the Nagel anomaloscope matching range in anomalous trichromatism

The Farnsworth D15 test (D15) was developed for use in occupational guidance. People with significant color deficiency, including all dichromats are expected to fail and people with slight color deficiency are expected to pass. Pass is a circular results diagram and fail an interlacing pattern with one or more red-green isochromatic errors (Farnsworth, 1947). The Nagel anomaloscope is a "gold standard" reference test for identifying and classifying red-green color deficiency. The matching range on the red/green mixture scale indicates the severity of the discrimination deficit. Pass/fail results for the D15 are presented for 107 protanomalous and 410 deuteranomalous trichromats and compared with the anomaloscope matching range. Thirty-six percent of the subjects examined failed the D15. Protanomalous trichromats are able to utilize perceived luminance contrast to obtain good results on the D15 but 42% of these subjects failed the D15 compared with 35% of deuteranomalous subjects. Failure of the D15 was clearly related to the Nagel matching range in deuteranomalous trichromatism but not in protanomalous trichromatism. For example, 84% of deuteranomalous subjects with matching ranges > 30 scale units failed the D15 but only 2% with matching ranges 15 scale units and 33% of subjects with matching ranges < 5 scale units were unsuccessful. Protanomalous trichromats with apparently minimal color deficiency are therefore shown to have poor practical hue discrimination ability as measured with this test.

A study of unusual Rayleigh matches in deutan deficiency

Rayleigh match data were modeled with the aim of explaining the locations of match midpoints and matching ranges, both in normal trichromats and in subjects with congenital color deficiency. Model parameters included the wavelength of peak sensitivity of cone photopigments, the effective photopigment optical density, and the noise amplitude in the red-green color channel. In order to avoid the suprathreshold, perceptual effects of extreme L:M cone ratios on color vision, selective post-receptoral amplification of cone signals is needed. The associated noise is also amplified and this causes corresponding changes in red-green threshold sensitivity. We propose that the noise amplitude and hence the size of the matching range in normal trichromats relates to the known inter-subject variation in the relative numbers of L and M cones. If this hypothesis can be shown to account for the extremes of the red-green matching range measured in normal trichromats, it is of interest to establish the extent to which it also predicts the unexpected, small matching ranges that are observed in some subjects with red-green color deficiency. A subset of subjects with deutan deficiency that exhibited less common Nagel matches were selected for genetic analysis of their cone pigment genes in order to confirm the type of deficiency, and to predict the corresponding peak wavelength separation (delta lambda(max)) of their two, long-wavelength cone pigments. The Rayleigh match model predicted accurately the midpoint and the range for the spectral differences specified by the genes. The prediction also required plausible selection of effective optical density of the cone pigments and noise. The noise needed varied, but the estimates were confined to lie within the limits established from the matching ranges measured in normal trichromats. The model predicts correctly the small matching ranges measured in some deuteranomalous subjects, principally accounted for by a low estimate of noise level in the red-green channel. The model also predicts the "normal" matches made by some subjects that rely on two hybrid genes and therefore exhibit red-green thresholds outside the normal range, typical of mild deuteranomaly.

Pass rates for the Farnsworth D15 colour vision test

The Farnsworth D15 test (D15) is used worldwide to select applicants for employment in occupations which require good colour vision. People with slight colour deficiency are intended to pass the D15 and people with significant (moderate/severe) colour deficiency to fail. Pass rates were determined for 710 adult males with red-green colour deficiency using three different pass criteria in general use. Forty-six per cent of subjects were successful when the pass criterion was a circular results diagram (one single transformation of adjacent hues was accepted as a pass), 53% passed when one red-green isochromatic error was allowed and 60% passed when two red-green isochromatic errors were permitted. The pass rate for 200 dichromats was 1.5% on a circular diagram, 3% on one red-green error and 6% on two red-green errors. Protans made fewer errors than deutans and more protans than deutans were successful when either one or two red-green crossings were permitted as a pass. A circular results diagram is the preferred pass criterion. This criterion most nearly fulfils the aim of the test to fail all dichromats and people with significant protanomalous and deuteranomalous trichromatism. A circular diagram is also easy to interpret consistently. Re-examination is recommended if there are only one or two red-green isochromatic error lines across the results diagram. This gives individuals with borderline slight/moderate colour deficiency an opportunity to pass at the second attempt.

Performance of colour‐deficient people on the Holmes–Wright lantern (type A): consistency of occupational colour vision standards in aviation

The Holmes-Wright lantern type A (H-W A) is an occupational colour vision test used by the UK Civil Aviation Authority (CAA) and approved by Joint Aviation Requirements (JAR) to select aircrew. Pass, to obtain a CAA Class 1 Aviation medical certificate, can be achieved at three stages of the examination. The Commission Internationale d'Eclairage (CIE) recommends that the Falant pass criteria are used with all approved lanterns. A pass to obtain CIE Colour Vision Standard 2 can be achieved at two stages of the examination. This study examines the consistency of these pass criteria. One hundred and twenty-five men with red-green colour deficiency were examined. All subjects completed three runs of the nine colour pairs shown on the H-W A at high brightness, in photopic and scotopic viewing. Ten of 78 deuteranomalous trichromats examined passed to obtain a CAA Class 1 Aviation medical certificate at the first stage of the examination but only two of these subjects were successful at all three stages. Seventeen deuteranomalous trichromats passed to obtain CIE Colour Vision Standard 2 in photopic viewing and 20 subjects (one protanope and 19 deuteranomalous trichromats) passed in scotopic viewing. Only 50% of subjects who passed at the first stage of the examination were also successful at the second stage in either viewing condition. Ten deuteranomalous trichromats passed to obtain CIE Colour Vision Standard 2 in both photopic and scotopic viewing. Forty-three per cent of subjects made red-green errors and 79% made red-white errors at some stage of the examination. The staged pass criteria used by the CAA and the CIE lack internal consistency when applied to the H-W A. Colour-deficient people who pass to a standard at the first stage of the examination are unlikely to be successful if the examination is continued. The staged pass criteria do not identify individuals with superior colour discrimination ability and it is difficult to justify selection of personnel for high risk occupations in aviation on this basis.

Comparison of nonius horopter for different wavelengths between color normal and color deficients

This study evaluated the effect of color on nonius horopter between color normal and color deficient subjects. Horopter curves were plotted and analyzed for blue (450 nm), green (518 nm), yellow (589 nm) and red (634 nm) wavelengths in four subjects. Color normals and color deficient subjects showed similar horopter plots. One color normal and one color deficient subject perceived red horopter in front of blue and the other two subjects had the opposite effect. Based on these results it was concluded that the changes seen in the horopter for the different wavelengths is purely an optical effect with the primary cause being chromostereopsis due to chromatic aberration.

Colour vision screening among Saudi Arabian children

Purpose: To determine the prevalence of congenital red-green colour vision defects among Saudi Arabian male and female children.Methods: The study involved 1638 elementary and high school participants (838 males, and 800 females), who were randomly selected and screened for red-green colour vision defects using the Ishihara (pseudo-isochromatic plates) test. Inclusion criteria were Snellen VA 20/20 or better and absence of known ocular pathologies.Among the females, 0.75% of the 800 participants showed CVD, with 0.25% and 0.5% demonstratingprotan and deutan defects, respectively.Conclusion: The results show that the prevalence of red-green colour deficiency among the female children from central Saudi Arabia is not significantly different from that of female populations inwestern countries. The current prevalence among the males is higher than previously reported for central Saudi Arabia, but less than for Caucasian populations.

John Dalton: Though in Error, He Still Influenced Our Understanding of Congenital Color Deficiency

John Dalton was born in the 18th century and was recognized mainly for his work on the chemical atomic theory and “Dalton's Law” for the partial pressure of gases. However, during his lifetime he was already recognized for his theories on “colorblindness,” with which he was afflicted. He was perhaps the first to report personal observations from experimentation on his color vision deficiency. His theory regarding its pathogenesis was posthumously proven to be incorrect after observations performed on his enucleated eyes. Further generations later, DNA analyses by PCR conclusively recorded the specific color deficiency (deuteranopia) with which Dalton was affected.

2P1-D03 カラーユニバーサルデザインを考慮したATM画面の設計(ユニバーサルデザイン)

This paper provides the study on the automated teller machine's display in consideration of the color universal design. Color universal design is an approach to the design of products and environments to be usable by visual disabilities, including persons with color deficiency. We determine the suitable button size and the color arrangement of ATM's display by means of the results of the questionnaire. We evaluate the usability of the ATM using the computer simulation.

Information Preserving Color Transformation for Protanopia and Deuteranopia

In this letter, we proposed a new recoloring method for people with protanopic and deuteranopic color deficiencies. We present a color transformation that aims to preserve the color information in the original images while maintaining the recolored images as natural as possible. Two error functions are introduced and combined together to form an objective function using the Lagrange multiplier with a user-specified parameter lambda. This objective function is then minimized to obtain the optimal settings. Experimental results show that the proposed method can yield more comprehensible images for color-deficient viewers while maintaining the naturalness of the recolored images for standard viewers.

The effect of acquired colour deficiency in elderly people on some aspects of sleep

It has been reported that elderly people have various difficulties with biological rhythms. However, there are few reports concerning associations between receiving light during the daily routine, colour deficiency and sleep quality. The present study investigated these relationships by using a light and activity monitor (Actiwatch-L) and the desaturated 15-hue colour test. Twenty-four healthy elderly participants took part in the experiment and were classified into Normal, Low, and High levels with regard to acquired colour deficiency. Physical activity and the quantities of light received by the participants during the daytime and night-time were not significantly different between the three groups. ANOVA indicated that “Actual Wake rate (%)” was significantly different (p = 0.0221). Post hoc tests showed that it was significantly different between Normal and High (p < 0.05). These results support the view that an increase in colour deficiency with age alters sleep quality.

Cone selectivity derived from the responses of the retinal cone mosaic to natural scenes.

To achieve color vision, the brain has to process signals of the cones in the retinal photoreceptor mosaic in a cone-type-specific way. We investigated the possibility that cone-type-specific wiring is an adaptation to the statistics of the cone signals. We analyzed estimates of cone responses to natural scenes and found that there is sufficient information in the higher order statistics of L- and M-cone responses to distinguish between cones of different types, enabling unsupervised learning of cone-type specificity. This was not the case for a fourth cone type with spectral sensitivity between L and M cones, suggesting an explanation for the lack of strong tetrachromacy in heterozygous carriers of color deficiencies.

Color vision in horses (Equus caballus): Deficiencies identified using a pseudoisochromatic plate test.

In the past, equine color vision was tested with stimuli composed either of painted cards or photographic slides or through physiological testing using electroretinogram flicker photometry. Some studies produced similar results, but others did not, demonstrating that there was not yet a definitive answer regarding color vision in horses (Equus caballus). In this study, a pseudoisochromatic plate test--which is highly effective in testing color vision both in small children and in adult humans--was used for the first time on a nonhuman animal. Stimuli consisted of different colored dotted circles set against backgrounds of varying dots. The coloration of the circles corresponded to the visual capabilities of different types of color deficiencies (anomalous trichromacy and dichromacy). Four horses were tested on a 2-choice discrimination task. All horses successfully reached criterion for gray circles and demonstration circles. None of the horses were able to discriminate the protan-deutan plate or the individual protan or deutan plates. However, all were able to discriminate the tritan plate. The results suggest that horses are dichromats with color vision capabilities similar to those of humans with red-green color deficiencies.

Visual-Evoked Potentials to Onset of Chromatic Red-Green and Blue-Yellow Gratings in Parkinson’s Disease Never Treated With L-Dopa

The differential dysfunction of chromatic and achromatic visual pathways in early Parkinson's disease (PD) was evaluated by means of visual-evoked potentials (VEPs) recorded in 12 patients (mean age 60.1 +/- 8.3 years; range 46 to 74 years) in the early stages of PD and not yet undergoing treatment with L-dopa, and in 12 age-matched controls. Visual stimuli were full-field (14 deg) equiluminant red-green (R-G), blue-yellow (B-Y), and black-white (B-W) sinusoidal gratings of two cycles per degree, presented in onset (300 milliseconds)--offset (700 milliseconds) mode, at two contrast (K) levels (90% and 25%). The VEP mean latencies were significantly more delayed in PD patients than in controls for chromatic than for luminance stimuli, in particular for B-Y stimuli of low contrast (K90%: B-W = 6.6 milliseconds, R-G = 3.34 milliseconds, B-Y = 15.48 milliseconds; K25%: B-W = 7.8 milliseconds, R-G = 14.8 milliseconds, B-Y = 28.9). Latencies of chromatic VEPs were more variable that achromatic VEP latencies in both normal subjects and PD patients. Therefore, the frequency of latency abnormalities (within 30%) was not significantly different for the three visual stimuli. Our results show that, in addition to achromatic VEPs, chromatic VEPs are impaired in early PD patients not yet undergoing L-dopa therapy, indicating an acquired color deficiency in these patients. The greater delay for the B-Y VEPs suggests a higher vulnerability of visual blue-cone pathway in the early stages of the disease. However, the overall sensitivity of chromatic VEPs in detecting early visual impairment in PD is comparable with that of achromatic VEPs.

Ophthalmological and otological problems in Turner syndrome

Ocular abnormalities are common in Turner syndrome (TS). They include epicanthal folds, ptosis, and hypertelorism. Red–green color deficiency is also more common in TS. Non-familial strabismus and hyperopia occur in 25–25% of TS children. To prevent visual loss, children with TS should be evaluated by a pediatric ophthalmologist at 12–18 months of age. Hearing problems and ear malfunctions are also common in TS and correlate with the karyotype. As a result of the frequent otitis media, conductive hearing loss is common in girls with TS. Sensorineural hearing loss is also common and may occur as early as 6 years of age. It is usually manifest by a sensorineural dip in the 1.5–2 kHz region and/or high frequency loss (above 8 kHz). By middle age, the hearing deficit often has serious professional and social consequences and a quarter of the TS women will require hearing aids. Otitis media has to be treated aggressively. Currently the only possible intervention to reduce hearing loss in women with TS remains the assiduous treatment of ENT problems in childhood. Growth hormone treatment as well as estrogen treatment has no effect on the progression.

THE PREVALENCE OF VISUAL DEFECT AMONG COMMERCIAL VEHICLE DRIVERS IN SELANGOR, MALAYSIA

A cross-sectional survey of commercial vehicle drivers who were renewing their own licences was conducted at the Selangor Road Transport Department office in Padang Jawa between 1 February 2002 and 28 February 2002, using questionnaire and medical examination. The objective was to determine the prevalence of myopia, colourvision deficiency and visual field defect among the commercial vehicle drivers. The respondents that reported visual defect at the time of interview was compared with those detected by the author through medical examination. Out of the 223 respondents, 21 (9.4%) reported to have myopia by the questionnaire survey. Through the visual examination there were 63 (28.3%) with myopia (visual acuity worse than 6/12), six (2.6%) had a visual field defect and 14 (6.3%) had red-green colour deficiency. The visual defect detected during the study among the commercial vehicle drivers,which were missed at the time of the routine medical examination were significant. The process of the statutory medical examination should be reviewed.

Color discrimination in carriers of color deficiency

Carriers of X-linked color vision deficiencies have previously been reported to exhibit mild abnormalities of color matching and discrimination. In a sample of 55 carriers of protan and deutan deficiencies and 55 age-matched normal controls, we measured chromatic discrimination along a red-green axis. We found that discrimination was impaired in the case of carriers of deutan deficiencies (which affect the middle-wave-sensitive cones of the retina), but was normal in the case of carriers of protan deficiencies (which affect the long-wave-sensitive cones). We argue that this result can be explained by the difference in the relative numbers of middle- and long-wave cones in heterozygous retinae: the imbalance of the two cone types is predicted to be much greater in the case of the deutan heterozygote than in the case of the protan heterozygote. In future studies it will be necessary to consider separately the two types of heterozygote.

Evaluation of the New Web-Based “Colour Assessment and Diagnosis” Test

The purpose of the study was to determine the sensitivity, specificity, and repeatability of the web-based Colour Assessment and Diagnosis (CAD) test in comparison to current tests of color vision. Thirty color normals and 30 color deficients, identified and diagnosed by the Nagel anomaloscope, were tested. The results of the CAD test were compared with standard tests like Nagel anomaloscope, Ishihara (concise version, 2001), Hardy, Rand and Rittler (HRR; 4 ed) pseudoisochromatic test, and the Farnsworth Munsell 100 (FM-100) hue test. Using the Nagel anomaloscope as the "gold standard," the sensitivity with the CAD test was 93.33%, Ishihara 96%, HRR 100%, and the FM-100 hue 100%. The specificity was 100% with CAD and the Ishihara color plates, whereas it was 33% with the HRR and 83% with the FM-100 hue test. The concurrent validity of the CAD test for color normals was 93.75%. The concurrent validity of CAD test for color deficiency was 100%. Thus, anyone failing the CAD test has a color defect. The coefficient of agreement for the Nagel anomaloscope and the CAD test was 0.93, with Ishihara it was 0.96, with the HRR it was 0.33, and with FM-100 hue it was 0.83. These results showed that the CAD test is a valid test for identifying congenital red-green color deficiency. Further testing is required in a larger population of anomalous trichromats.