The purpose of this study was to optimise the testing paradigm for isolating the contributions of chromatic and achromatic mechanisms to the human spectral sensitivity function. Spectral sensitivity was determined for a test spot size of 1.2 deg presented with various spatial and temporal masks on a large, 10 deg background field of moderate intensity (1000 td) and colour temperature, CT = 2700 K. Sinusoidal temporal presentation (1 Hz) and a masking annulus of between 3 and 10 min of arc surrounding the test spot, was found to be most effective in separating chromatic from achromatic mechanisms. Square-wave (1 Hz) temporal presentation combined with the annulus was slightly less selective. The presence of the annulus did not affect the shape of flicker detection at 25 Hz which is a measure of the luminosity (achromatic) spectral sensitivity function.
The topcoat color of motor vehicles offers vital information while investigating vehicular accidents, especially in instance of hit-and-run, since witnesses seldom perceive and retain the plate details. Differences in color perceptions among individuals with normal vision may lead to confusion in determining the color of the car involved. In this way, witnesses of crash accidents could potentially initiate flawed leads in forensic investigation, and thus affect the administration of justice. In this study, the inter-rater reliability of vehicle color determination by different volunteers was explored. Six individuals observed the topcoat colors of 500 stationary and 500 moving vehicles from five locations, employing a common system of color gradation. The outcome was binary: the vehicle color was either a "match" or "non-match". This was followed by statistical analysis in terms of the colors' frequencies and inter-rater reliability, based on which more suitable color descriptions were determined for subsequent comparisons of stationary and moving vehicles. Higher match frequencies and greater inter-rater reliability were observed when color gradations were disregarded. The frequency of correct matches could have been closely related to their relative on-the-road distribution, regardless of the statuses of observed vehicles. It was also found that black and white were associated with a greater number of matches than were intermediate colors, which should be carefully interpreted during forensic investigation to avoid wrong leads. In conclusion, the present study demonstrated the forensic significance of vehicle topcoat color determination, particularly in cases where witness statements are crucial.
A study was undertaken to determine the effect of polyethylene and polystyrene used in the manufacture of plastic items on colour perception. Colour vision was assessed using the Ishihara plates, panel 015 test and the Farnsworth Munsell 100-Hue test. Two factories were chosen at random. One factory (referred here as factory A) used virgin resin in pellet form (polyethylene) in the manufacturing of plastic containers to store consumer edible oil. The other factory (referred as factory B) used polystyrene to make plastic bags. A total of 39 healthy employees from factory A (mean age 26.4 :t 8.2 years) and 40 healthy employees from factory B (mean age 26.8 :t 9.6 years) were recruited in this study. A control group of 27 normal healthy subjects (mean age 27.4 :t 4.3 years) who were employees of UKM with no occupational involvement with petroleum derivatives were also recruited in this study and they performed the same colour vision tests. All subjects passed the Ishihara plates test showing that none of the subjects (employees of factory A and B, and control subjects) had a congenital red-green defect. All control subjects passed all of the colour vision tests whilst some employees of factories A and B failed the 015 and FM100 Hue tests. For employees from factory A results from the 015 test showed that 7 (17.9%) had a tritan (blue-yellow) type of defect and 1 (2.6%) had a complex type of defect. The FM 100 Hue results of factory A employees showed that 51.3% (n=20) had a complex type of defect. Total error scores (TES) calculated from the FM 100 Hue test revealed that employees from factory A had a statistically significant higher mean TES of 65.13:!: 48.31 compared to that of control subjects with a mean TES of 31.26:!: 14.93. For employees in factory B, 10 employees (25.0%) had a tritan (blue-yellow) type of defect and 2 (5.0%) had a complex type of defect. Results of the FM 100 Hue test showed that 4 employees (1.0%) had a tritan type of defect whereas 22 (55.0%) had a complex type of defect. Mean total error scores (TES) calculated from the FM 100 Hue test revealed that employees from factory B had a statistically significant higher mean TES of 71.54 :t 54.63 compared with that of control subjects with a mean TES of 31.26 :t. 14.93
The above results show that employees of the plastic factories studies are associated with a higher risk of acquiring colour vision defects as compared to normal subjects who are not engaged in the plastic manufacturing industry. This may have an implication towards the future retinal health of employees in petrod1emical-based industries.
Matched MeSH terms: Color Perception; Color Perception Tests
BACKGROUND: This prospective study was undertaken to investigate whether spectral sensitivity can be useful in determining the prognosis of fellow eyes of eyes with macular holes.
METHODS: Spectral sensitivity measurements using a one degree test spot presented at a rate of 1 Hz and 25 Hz on a bright (1000 td) white background were carried out on 10 patients aged between 67 and 74 years (mean age 70.3 +/- 2.6 years). Each patient had a full thickness macular hole in one eye and a normal contralateral fellow eye. The spectral sensitivity measurements were made with eccentric fixation in the eyes with macular holes and with central fixation in the normal fellow eye. A year later, the patient files were reviewed to look at the patient's ocular condition. Another 10 subjects between the ages of 50 and 80 years (mean age 69.5 +/- 4.2 years) were also seen. These control group subjects had visual acuities of 6/9 or better with minimal ocular media changes and no ocular or systemic pathology that could affect colour vision.
RESULTS: The 1 Hz and 25 Hz spectral sensitivities of all patients were reduced for both eyes. Despite the good eye without a macular hole having a VA of 6/6, the spectral sensitivity was similar to that of the eye with the macular hole and markedly reduced visual acuity.
CONCLUSION: The present investigation enabled us to examine the chromatic and achromatic mechanisms by testing spectral sensitivity at 1 Hz and 25 Hz, respectively. The data revealed that both chromatic and achromatic processing could be damaged in the eye with a macular hole. Surprisingly, the spectral sensitivities of both 1 Hz and 25 Hz are equally reduced in the good fellow eye with no macular hole. A one-year follow-up showed that two of the 10 patients (20 per cent) did eventually develop a macular hole in the normal fellow eye. This indicates that there is some subclinical foveal dysfunction in the normal fellow eye, the nature of which is unclear.
Study site: Manchester Royal Eye Hospital (MREH), United Kingdom
Everyday language reveals how stimuli encoded in one sensory feature domain can possess qualities normally associated with a different domain (e.g., higher pitch sounds are bright, light in weight, sharp, and thin). Such cross-sensory associations appear to reflect crosstalk among aligned (corresponding) feature dimensions, including brightness, heaviness, and sharpness. Evidence for heaviness being one such dimension is very limited, with heaviness appearing primarily as a verbal associate of other feature contrasts (e.g., darker objects and lower pitch sounds are heavier than their opposites). Given the presumed bidirectionality of the crosstalk between corresponding dimensions, heaviness should itself induce the cross-sensory associations observed elsewhere, including with brightness and pitch. Taking care to dissociate effects arising from the size and mass of an object, this is confirmed. When hidden objects varying independently in size and mass are lifted, objects that feel heavier are judged to be darker and to make lower pitch sounds than objects feeling less heavy. These judgements track the changes in perceived heaviness induced by the size-weight illusion. The potential involvement of language, natural scene statistics, and Bayesian processes in correspondences, and the effects they induce, is considered.
Purpose. To highlight the importance of using the Farnsworth Panel D-15 Hue test in colour vision testing in patients on ethambutol treatment. Case Report. A 70 year-old lady received ethambutol as part of her anti-tuberculous regime. She developed blue-yellow colour defect detectable with the Farnsworth Panel D-15 Hue test, but not with the Isihara Pseudoisochromatic Plates. Ethambutol was immediately discontinued from her anti-tuberculous regime. Two months later, her colour vision returned to normal. Conclusion. This case report illustrates the importance of regular monitoring of patients receiving ethambutol for blue-yellow colour defect using the Farnsworth Panel D-15 Hue Test.
BACKGROUND: Occupational exposure to various neurotoxic chemicals has been shown to be associated with colour vision impairment. It seems that this can occur at low exposure levels, sometimes well below the recommended occupational threshold limits. This study was undertaken to determine the effect of exposure to petroleum derivatives (polyethylene, polystyrene) and solvents (perchloroethylene) on colour perception.
METHODS: Colour vision was assessed using the Ishihara plates, the D-15 test and the Farnsworth Munsell 100 Hue test. Two factories using petroleum derivatives and three dry cleaning premises were chosen at random. A total of 93 apparently healthy employees were recruited from the five workplaces. Two age-matched control groups comprising 56 people, who were support staff of the university with no exposure to petroleum, solvents or their derivatives, were also recruited.
RESULTS: All subjects passed the Ishihara test, showing that none had a congenital red-green defect. Some of the exposed employees failed the D-15 and had abnormally high FM100 Hue scores. All control subjects passed all the colour vision tests. The D-15 test showed that 28 per cent (26 of 93) of exposed employees had a colour vision defect whereas the FM 100 Hue test found that 63 per cent (59 of 93) had a colour vision defect. Most defects were of the blue-yellow type (22.6 per cent) when using the D-15 test. However, with the FM 100 Hue test, most defects were of the non-polar type with no specific axis (50.5 per cent). Mean total error scores calculated from the FM100 Hue test for exposed employees were statistically significantly higher than those of the control subjects.
CONCLUSION: Employees directly exposed to petroleum derivatives and solvents have a higher risk of acquiring colour vision defects compared to subjects who are not.
Study sites: Factories; the control subjects were tested at the Optometry Clinic in Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia.
Matched MeSH terms: Color Perception/drug effects*; Color Perception Tests
Colors and odors are associated; for instance, people typically match the smell of strawberries to the color pink or red. These associations are forms of crossmodal correspondences. Recently, there has been discussion about the extent to which these correspondences arise for structural reasons (i.e., an inherent mapping between color and odor), statistical reasons (i.e., covariance in experience), and/or semantically-mediated reasons (i.e., stemming from language). The present study probed this question by testing color-odor correspondences in 6 different cultural groups (Dutch, Netherlands-residing-Chinese, German, Malay, Malaysian-Chinese, and US residents), using the same set of 14 odors and asking participants to make congruent and incongruent color choices for each odor. We found consistent patterns in color choices for each odor within each culture, showing that participants were making non-random color-odor matches. We used representational dissimilarity analysis to probe for variations in the patterns of color-odor associations across cultures; we found that US and German participants had the most similar patterns of associations, followed by German and Malay participants. The largest group differences were between Malay and Netherlands-resident Chinese participants and between Dutch and Malaysian-Chinese participants. We conclude that culture plays a role in color-odor crossmodal associations, which likely arise, at least in part, through experience.
The majority of patients with dysthyroid eye disease have an acquired colour vision defect. However, no psychophysical investigation of selective damage to colour or flicker pathways has been carried out. In order to clarify the nature of the visual pathology, we have used a psychophysical technique (spectral sensitivity) to selectively stimulate the chromatic and achromatic mechanisms. Spectral spots of size 1 degree presented at a rate of 1 Hz on a bright 1000 td white background are detected by the chromatic mechanism but a rate of 25 Hz reveals the achromatic mechanism. Fifteen patients (28 eyes) between the ages of 50-70 years were tested. The study showed that all patients had reduced spectral sensitivity, either 1 Hz, 25 Hz or both. The patients with reduced 1 Hz or 25 Hz spectral sensitivity only had a shorter systemic and ocular duration of the condition, had no proptosis, normal intraocular pressures in primary gaze, slightly higher intraocular pressures on upgaze, normal visual field plots and FM 100-Hue error scores higher than the normal age-matched values. The patients with reduced both 1 Hz and 25 Hz spectral sensitivities had a longer systemic and ocular duration of the condition, had proptosis, normal intraocular pressures in primary position, higher intraocular pressures on upgaze and higher FM 100-Hue error scores than the age-matched normals and those in Groups 1 and 2. A total of 50% of patients in Group 3 had defective visual field plots. These data suggest that there is a damage of the large achromatic fibres and small chromatic fibres in dysthyroid eye disease. The mechanism of the damage could be one of ischaemic or mechanical or both.
Human facial skin colour reflects individuals' underlying health (Stephen et al 2011 Evolution & Human Behavior 32 216-227); and enhanced facial skin CIELab b* (yellowness), a* (redness), and L* (lightness) are perceived as healthy (also Stephen et al 2009a International Journal of Primatology 30 845-857). Here, we examine Malaysian Chinese participants' detection thresholds for CIELab L* (lightness), a* (redness), and b* (yellowness) colour changes in Asian, African, and Caucasian faces and skin coloured patches. Twelve face photos and three skin coloured patches were transformed to produce four pairs of images of each individual face and colour patch with different amounts of red, yellow, or lightness, from very subtle (deltaE = 1.2) to quite large differences (deltaE = 9.6). Participants were asked to decide which of sequentially displayed, paired same-face images or colour patches were lighter, redder, or yellower. Changes in facial redness, followed by changes in yellowness, were more easily discriminated than changes in luminance. However, visual sensitivity was not greater for redness and yellowness in nonface stimuli, suggesting red facial skin colour special salience. Participants were also significantly better at recognizing colour differences in own-race (Asian) and Caucasian faces than in African faces, suggesting the existence of cross-race effect in discriminating facial colours. Humans' colour vision may have been selected for skin colour signalling (Changizi et al 2006 Biology Letters 2 217-221), enabling individuals to perceive subtle changes in skin colour, reflecting health and emotional status.
People struggle to name odors [1-4]. This has been attributed to a diminution of olfaction in trade-off to vision [5-10]. This presumption has been challenged recently by data from the hunter-gatherer Jahai who, unlike English speakers, find odors as easy to name as colors [4]. Is the superior olfactory performance among the Jahai because of their ecology (tropical rainforest), their language family (Aslian), or because of their subsistence (they are hunter-gatherers)? We provide novel evidence from the hunter-gatherer Semaq Beri and the non-hunter-gatherer (swidden-horticulturalist) Semelai that subsistence is the critical factor. Semaq Beri and Semelai speakers-who speak closely related languages and live in the tropical rainforest of the Malay Peninsula-took part in a controlled odor- and color-naming experiment. The swidden-horticulturalist Semelai found odors much more difficult to name than colors, replicating the typical Western finding. But for the hunter-gatherer Semaq Beri odor naming was as easy as color naming, suggesting that hunter-gatherer olfactory cognition is special.
Visual cognitive function is important in the construction of executive function in daily life. Perception of visual number form (e.g. Arabic digits) and numerosity (numeric magnitude) is of interest to cognitive neuroscientists. Neural correlates and the functional measurement of number representations are complex events when their semantic categories are assimilated together with concepts of shape and color. Color perception can be processed further to modulate visual cognition. The Ishihara pseudoisochromatic plates are one of the best and most common screening tools for basic red-green color vision testing. However, there has been little study of visual cognitive function assessment using such pseudoisochromatic plates. 25 healthy normal trichromat volunteers were recruited and studied using a 128-sensor net to record event-related electroencephalogram. Subjects were asked to respond by pressing numbered buttons when they saw the number and non-number plates of the Ishihara color vision test. Amplitudes and latencies of N100 and P300 event related potential components were analyzed from 19 electrode sites in the international 10-20 system. A brain topographic map, cortical activation patterns, and Granger causation (effective connectivity) were analyzed from 128 electrode sites. No significant differences between N100 event related potential components for either stimulus indicates early selective attention processing was similar for number and non-number plate stimuli, but non-number plate stimuli evoked significantly higher amplitudes, longer latencies of the P300 event related potential component with a slower reaction time compared to number plate stimuli imply the allocation of attentional load was more in non-number plate processing. A different pattern of the asymmetric scalp voltage map was noticed for P300 components with a higher intensity in the left hemisphere for number plate tasks and higher intensity in the right hemisphere for non-number plate tasks. Asymmetric cortical activation and connectivity patterns revealed that number recognition occurred in the occipital and left frontal areas where as the consequence was limited to the occipital area during the non-number plate processing. Finally, results demonstrated that the visual recognition of numbers dissociates from the recognition of non-numbers at the level of defined neural networks. Number recognition was not only a process of visual perception and attention, but was also related to a higher level of cognitive function, that of language.
Multifocal pupillographic objective perimetry (mfPOP) has recently been shown to be able to measure cortical function. Here we assessed 44 regions of the central 60 degrees of the visual fields of each eye concurrently in 7 minutes/test. We examined how foveally- and peripherally-directed attention changed response sensitivity and delay across the 44 visual field locations/eye. Four experiments were completed comparing white, yellow and blue stimulus arrays. Experiments 1 to 4 tested 16, 23, 9 and 6 subjects, 49/54 being unique. Experiment 1, Experiments 2 and 3, and Experiment 4 used three variants of the mfPOP method that provided increasingly improved signal quality. Experiments 1 to 3 examined centrally directed attention, and Experiment 4 compared effects of attention directed to different peripheral targets. Attention reduced the sensitivity of the peripheral locations in Experiment 1, but only for the white stimuli not yellow. Experiment 2 confirmed that result. Experiment 3 showed that blue stimuli behaved like white. Peripheral attention showed increased sensitivity around the attentional targets. The results are discussed in terms of the cortical inputs to the pupillary system. The results agree with those from multifocal and other fMRI and VEP studies. mfPOP may be a useful adjunct to those methods.