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PubMed1993

[Reference to the Abney effect within the scope of linear opponent-color theory].

The Abney effect states that desaturation of spectral colours does not only change their chromatic saturation but also their hue. By means of Hering's perceptual criteria "neither blue nor yellow" and "neither green nor red" and heterochromatic brightness matching, chromaticity loci were measured in a visual tri-stimulus colorimeter; the loci served for construction of an opponent-colour triangle and the associated opponent-colour space. The chromaticity line resulting from the perceptual criterion "neither green nor red" deviated markedly--as an expression of the Abney effect--from a straight line. This phenomenon was captured by piecewise linearizing. The transformation of the (known) fundamental colour space, which may be interpreted as a cone excitation space, onto the opponent colour space thus gained yielded an explicit opponent-colour theory that reproduces some aspects of the Abney effect.

Color Perception↗
PubMed1995

The dyschromatopsia of optic neuritis: a descriptive analysis of data from the optic neuritis treatment trial.

PURPOSE: We sought to characterize the dyschromatopsia of optic neuritis, to determine the type and severity of color defect present and its relation to central vision and spatial acuity, to examine changes in this dyschromatopsia over time, and to determine the applicability of Köllner's rule to patients with optic neuritis. METHODS: We analyzed the raw data on color vision performance as assembled within the Optic Neuritis Treatment Trial (ONTT). The ONTT was designed to evaluate corticosteroids as a treatment for acute demyelinating optic neuritis and to allow long-term outcome and natural history analyses. Between July 1, 1988 and June 30, 1991, 488 patients were enrolled in this trial. All patients underwent extensive neurologic and ophthalmologic examinations including standardized testing of visual function that included testing of color vision. The ONTT population thus afforded a unique opportunity to characterize acquired dyschromatopsias in a large, homogenous, well-characterized cohort of patients with optic neuritis. We used quantitative analysis of FM-100 scores from this patient cohort to determine the severity of the dyschromatopsia, the selectivity of the dyschromatopsia (polarity of errors) and the type of dyschromatopsia (axis of confusion) by employing quadrant analysis of FM-100 scores. RESULTS: The results of high-and low-selectivity analyses of the FM-100 data showed that during the acute phase of optic neuritis, blue/yellow, red/ green, and non-selective color defects occurred; among patients with pure defects, blue/yellow defects were more frequent than red/green defects. At 6 months after the acute event, however, analyses showed that red/green defects were more common than blue/yellow defects. Among patients with selective color defects both acutely and at 6 months, the defect was as likely to change over time as remain the same. The likelihood of persistent dyschromatopsia at 6 months was related to the severity of initial central acuity loss, but the type of dyschromatopsia present (red/green versus blue/yellow) was not. CONCLUSIONS: Our results suggest that at the time of the acute attack of optic neuritis, the majority of selective color defects were blue/yellow defects, whereas at 6 months, more of the selective defects were red/green defects, though both types of defects (as well as nonselective defects) were seen acutely and at 6 months. Despite the rigorous inclusion criteria of the ONTT, the large number of patients we studied, correlation of color vision with visual acuity, and longitudinal follow up, this study showed that no single type of color defect was consistently associated with optic neuritis. Demyelinating optic neuritis does not obey Köllner's rule. Moreover, the type of defect present changed in some patients over the course of recovery. Thus, the type of defect may not even be consistent in individual patients as they recover. The type of defect appeared to be related to spatial vision at the time of the test, but the type of defect present at 6 months was not related to the severity of the initial visual loss. Therefore, in evaluating color defects associated with optic neuritis, the level of central visual function must be considered.

Acute Disease↗
PubMed1995

Colour contrast sensitivity in patients with age-related Bruch's membrane changes.

Patients with bilateral drusen as a manifestation of early age-related macular degeneration (AMD) may have minor psychophysically detectable visual defects in the presence of normal visual acuity. In a variety of retinal diseases, one of the earliest changes in visual processing is an impairment of normal colour vision. This study was undertaken to evaluate colour vision deficits in patients with macular drusen and to determine whether changes in colour contrast sensitivity may occur over time. In a prospective study, colour vision in 84 eyes of 84 patients aged 55-84 years (mean, 68.89 +/- 6.23 years) with macular drusen and clear media was tested using a computer graphics technique. A total of 47 patients were reviewed annually for up to 2 years and measurements were obtained at annual intervals. Colour contrasts sensitivity along protan, deutan and tritan colour confusion lines was determined at a foveal and a parafoveal region. The sensitivity to all stimuli showed large variations between patients. The thresholds for foveal blue-colour contrast sensitivity were elevated and increased during the review period. In contrast, there was no significant change in sensitivity with time for red and green at the foveal or parafoveal region. Tritan threshold changes suggest that the SW cone-receptor population is more susceptible to damage associated with early age-related macular disease than are red or green cones. The results indicate that blue colour contrast sensitivity determined over time may serve as a measure to assess the progression of age-related maculopathy prior to the manifestation of atrophic or exudative macular lesions associated with visual loss.

Aged↗
PubMed1996

Foveal color and luminance sensitivity losses in glaucoma.

BACKGROUND AND OBJECTIVE: Losses in color vision sensitivity are noted in patients with glaucoma and these losses can occur before the onset of visual field defects in ocular hypertensive patients. The authors incorporate a technique that measures foveal luminance and isoluminant-color thresholds. PATIENTS AND METHODS: This study included 31 patients with glaucoma, 10 patients suspected of having glaucoma, and 67 control subjects. The testing conditions measured thresholds under identical spatial and temporal conditions. Individual differences in luminosity between colors were controlled by presenting 16 different ratios of the three phosphors on a color monitor. RESULTS: Relative to the control subjects, the patients with glaucoma showed a nonselective defect in both color and luminance sensitivity for red-green stimuli (P < .05), but a selective color defect for yellow-blue stimuli (P < .01). There were no statistically significant differences between patients suspected of having glaucoma and control subjects (P > 0.3). CONCLUSION: If the isoluminant-color stimuli are detected by foveal P-ganglion cells, then these results suggest that glaucoma leads to a generalized decrease in P-ganglion cell sensitivity that is more pronounced for cells with an input from cones sensitive to short wavelengths.

Adult↗
PubMed1996

Comparison of the standard pseudoisochromatic plates--Parts 1 and 2--As screening tests for congenital red-green color vision deficiencies.

BACKGROUND: The Standard Pseudoisochromatic Plates-Part 2 (SPP-2) are designed primarily as a screening test for acquired color vision deficiencies. However, results from several studies suggest that the SPP-2 may also be effective as a screening test for congenital red-green color vision defects. METHODS: In this study, the screening effectiveness of the SPP-2 was compared with the Standard Pseudoisochromatic Plates-Part 1 (SPP-1) to determine whether clinicians must use both tests: the SPP-1 to screen for congenital color vision defects and the SPP-2 to screen for acquired color vision defects. RESULTS: The results showed that, when using the recommended scoring criterion for the SPP-1, the SPP-2 test is slightly more sensitive in detecting congenital red-green defects. CONCLUSIONS: Clinicians can use the SPP-2 to screen for both congenital and acquired color vision defects.

Adolescent↗
PubMed1996

Color vision measured with pseudoisochromatic plates at five-and-a-half years in eyes of children from the CRYO-ROP study.

PURPOSE: To investigate the prevalence of color deficits at age 5 1/2 years in preterm children with birth weights of less than 1251 g who participated in the multicenter Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) study. METHODS: Two cohorts of CRYO-ROP participants served as subjects: 1055 children who participated in a long-term study of the natural history of ROP at 5 of the 23 CRYO-ROP centers, and 187 children (from all 23 study centers) who had threshold ROP in both eyes and who were randomized to receive cryotherapy in 1 eye. Monocular color vision was tested at age 5 1/2 years, using the Standard Pseudoisochromatic Plates, part 2 (SPP2) for acquired color vision defects. RESULTS: In the Natural History cohort, prevalence of red-green (R-G) color deficits was 6.6% for males and 1.0% for females, similar to that of the general adult population. Prevalence of blue-yellow (B-Y) color deficits was 2.8% for males and 2.2% for females, more than 200 times that in the general adult population. Prevalence of B-Y deficits was not related to birth weight, gestational age, acute-phase ROP, optic atrophy, or retinal residua of ROP, but was related to visual acuity. In the Threshold ROP cohort, color vision deficits were no more likely in eyes that had received cryotherapy than in control eyes. CONCLUSIONS: The results confirm an increased prevalence of B-Y deficits in children born before term, and provide evidence that the increased prevalence is not related to birth weight, gestational age, or severity of ROP within this group of preterm children. No evidence was found to indicate that cryotherapy increased the rate of color vision deficits in eyes with threshold ROP.

Birth Weight↗
PubMed1996

Cone-specific measures of human color vision.

PURPOSE: To describe a new test of color vision (cone-specific contrast sensitivity) and to evaluate its sensitivity in comparison to standard clinical tests. METHODS: Cone-specific colored letter charts were generated by computer and displayed on a color monitor. Each chart consists of colored letters that are most visible at the top but that gradually fade into a gray background. Cone contrast varies systematically on each chart so that letters are visible to only one cone type (L, M, or S cone). Cone-specific letter contrast sensitivity was measured in 30 color normals and 13 subjects with hereditary color deficiency. Values were compared to standard measures of color vision. RESULTS: In color normals, mean log contrast sensitivity was approximately the same on L-cone (1.84 +/- 0.08 log contrast sensitivity) and M-cone (1.87 +/- 0.08) tests but was reduced on the S-cone test (0.89 +/- 0.15) because of the fewer number of S-cones in the human retina. Subjects with red color deficiency showed significantly reduced contrast sensitivity on the L-cone test but normal performance on M- and S-cone tests. Subjects with green color deficiency showed decreased contrast sensitivity limited to the M-cone test. When standardized relative to variability, cone contrast sensitivity identified color deficiency unequivocally in all subjects, whereas FM 100 hue error scores detected 9 of 13 subjects with color deficiency. CONCLUSIONS: Cone-specific contrast sensitivity provides a quantitative measure of normal color vision and indicates both type and severity of color deficiency. It is useful for diagnosing hereditary color deficiency and for monitoring early color vision loss in ocular and systemic disease.

Adult↗
PubMed1997

Evaluation of a significantly shorter version of the Farnsworth-Munsell 100-hue test in patients with three different optic neuropathies.

We tested the hypothesis that a subset of the Farnsworth-Munsell 100-hue test (FM-100) would be a sensitive, specific, and practical means of monitoring color vision in patients with chronic optic nerve disorders. We retrospectively analyzed the records of 1,113 patients affected with optic neuritis (ON), Graves' ophthalmopathy with suspected optic neuropathy, or idiopathic intracranial hypertension with suspected optic neuropathy (IIH). One hundred six records of patients showed that an FM-100 had been performed (23 ON, 46 Graves', 37 IIH). Forty additional patients were studied prospectively (11 ON, 17 Graves', 12 IIH). The sensitivity and specificity of all possible 21 chip subtests were compared against the same statistics for the entire test. We found that for these three optic nerve disorders, a test consisting of chips 22-42 had nearly the same sensitivity and specificity as the entire test when compared with the clinical diagnosis. At 90% specificity, the ratio of sensitivities of the short version to the original version of the test were IIH, 53%/45%; optic neuritis, 85%/79%; and Graves', 67%/70%. The majority of the clinical value of the test can be achieved in one fourth of the original examination time.

Adult↗
PubMed2001

The location problem for color subjectivism.

According to color subjectivism, colors are mental properties, processes, or events of visual experiences of color. I first lay out an argument for subjectivism founded on claims from visual science and show that it also relies on a philosophical assumption. I then argue that subjectivism is untenable because this view cannot provide a plausible account of color perception. I describe three versions of subjectivism, each of which combines subjectivism with a theory of perception, namely sense datum theory, adverbialism, and the virtual color proposal, and argue that each version faces serious objections. Considering these three theories of perception to be exhaustive of those available to the subjectivist, I conclude that subjectivism is untenable and that the scientifically motivated argument for this view is unsound. I then offer the diagnosis that the philosophical assumption on which this argument relies is mistaken.

Color Perception↗
PubMed2002

Spatiotemporal configuration dependent pairing of nerve events in dark-adapted human vision.

In the model presented here, in the dark any single quantum absorption in a rod or cone produces a subliminal excitation. Subliminal excitations from both halves of a twin unit pair in the retina for the perception of light from the stimulus. A twin unit contains either two red or two green cones. The twin units are intertwined in triples of two red units and one green unit in a hexagon called a trion. P satellite rods surround each cone, P being approximately proportional to the square of eccentricity. A successful pairing for light perception represents-through the points of time and locations of the creation of its partners in the retina--a direction event with two possible polarities and with the orientation of the elongated shape of the twin unit. The polarity of the event depends on which of the two partners arrives first at the twin's pairing facility. Simultaneous events and successive events with the same polarity in adjacent units that are aligned along one of the three orientations of the hexagonal retinal mosaic pair in the cortex for the perception of edge and of movement. Inter-twin pairing products of the three differently oriented sets of aligned twins are independent of each other and sum vectorially in the cortex. This system of three sub-retinas is called the retrinet. Two one-quantum excitations in any of a twin's receptors make the percept colored. The odd blue cone produces already a blue signal for a single one-quantum excitation. Intra-receptor pairing in a rod, a red cone and a green cone is for white, red, and green respectively. Red and green cone products of a trion cross-pair in the retina and produce a yellow signal. Red and green cone products of a hexagon of adjacent trions cross-pair in the cortex and produce a white signal. This large hexagon with a total of seven trions is called a persepton. After subliminal excitations in a twin have paired successfully, further subliminal receptor excitations in neighboring and aligned twins are expressed to a certain extent in the percept's area, duration and color. Earlier experiments on absolute and color thresholds are the basis for this theory, which is developed in this paper.

Color Perception↗
PubMed2006

Does binding of synesthetic color to the evoking grapheme require attention?

The neural mechanisms involved in binding features such as shape and color are a matter of some debate. Does accurate binding rely on spatial attention functions of the parietal lobe or can it occur without attentional input? One extraordinary phenomenon that may shed light on this question is that of chromatic-graphemic synesthesia, a rare condition in which letter shapes evoke color perceptions. A popular suggestion is that synesthesia results from cross-activation between different functional regions (e.g., between shape and color areas of the ventral pathway). Under such conditions binding may not require parietal involvement and could occur preattentively. We tested this hypothesis in two synesthetes who perceived grayscale letters and digits in color. We found no evidence for preattentive binding using a visual search paradigm in which the target was a synesthetic inducer. In another experiment involving color judgments, we show that the congruency of target color and the synesthetic color of irrelevant digits modulates performance more when the digits are included within the attended region of space. We propose that the mechanisms giving rise to this type of synesthesia appear to follow at least some principles of normal binding, and even synesthetic binding seems to require attention.

Adult↗
PubMed1997

Adaptation and the color statistics of natural images.

Color perception depends profoundly on adaptation processes that adjust sensitivity in response to the prevailing pattern of stimulation. We examined how color sensitivity and appearance might be influenced by adaptation to the color distributions characteristic of natural images. Color distributions were measured for natural scenes by sampling an array of locations within each scene with a spectroradiometer, or by recording each scene with a digital camera successively through 31 interference filters. The images were used to reconstruct the L, M and S cone excitation at each spatial location, and the contrasts along three post-receptoral axes [L + M, L - M or S - (L + M)]. Individual scenes varied substantially in their mean chromaticity and luminance, in the principal color-luminance axes of their distributions, and in the range of contrasts in their distributions. Chromatic contrasts were biased along a relatively narrow range of bluish to yellowish-green angles, lying roughly between the S - (L + M) axis (which was more characteristic of scenes with lush vegetation and little sky) and a unique blue-yellow axis (which was more typical of arid scenes). For many scenes L - M and S - (L + M) signals were highly correlated, with weaker correlations between luminance and chromaticity. We use a two-stage model (von Kries scaling followed by decorrelation) to show how the appearance of colors may be altered by light adaptation to the mean of the distributions and by contrast adaptation to the contrast range and principal axes of the distributions; and we show that such adjustments are qualitatively consistent with empirical measurements of asymmetric color matches obtained after adaptation to successive random samples drawn from natural distributions of chromaticities and lightnesses. Such adaptation effects define the natural range of operating states of the visual system.

Adaptation, Ocular↗
PubMed1997

Optic neuropathy associated with ethambutol in Koreans.

Ethambutol is a useful first line antituberculous drug, but can cause significant visual impairment. In order to determine the clinical manifestations of optic neuropathy associated with ethambutol, and the margin of drug safety in Koreans, we investigated ten men and four women, diagnosed between 1995 and 1997 at Seoul Municipal Boramae Hospital as suffering from ethambutol toxicity. After determining their history, including the period during which ethambutol had been administered, and its dose, a complete eye examination was performed, including measurement of best-corrected visual acuity, pupillary examination, color vision, fundus examination and a test of visual field. Ocular ethambutol toxicity was observed at a dose as low as 12.3 mg/kg. Abnormal ophthalmic findings include decreased visual acuity and abnormal visual field, especially in the central scotoma, and abnormal color perception. In conclusion, ethambutol at a low dose can cause optic neuropathy, and for the early detection of this, a color vision test is important.

Antitubercular Agents↗
PubMed2006

Effect of background colors on the tuning of color-selective cells in monkey area V4.

When objects are viewed in different illuminants, their color does not change or changes little in spite of significant changes in the wavelength composition of the light reflected from them. In previous studies, we have addressed the physiology underlying this color constancy by recording from cells in areas V1, V2, and V4 of the anesthetized monkey. Truly color-coded cells, ones that respond to a patch of a given color irrespective of the wavelength composition of the light reflected from it, were only found in area V4. In the present study, we have used a different approach to test the responses of V4 cells in both anesthetized and awake behaving monkeys. Stimuli of different colors, embedded within a Mondrian-type multicolored background, were used to identify the chromatic selectivity of neurons. The illumination of the background was then varied, and the tuning of V4 neurons was tested again for each background illumination. With anesthetized monkeys, the psychophysical effect of changing background illumination was inferred from our own experience, whereas in the awake behaving animal, it was directly reported by the monkey. We found that the majority of V4 neurons shifted their color-tuning profile with each change in the background illumination: each time the color of the background on the computer screen was changed so as to simulate a change in illumination, cells shifted their color-tuning function in the direction of the chromaticity component that had been increased. A similar shift was also observed in colored match-to-sample psychometric functions of both human and monkey. The shift in monkey psychometric functions was quantitatively equivalent to the shift in the responses of the corresponding population of cells. We conclude that neurons in area V4 exhibit the property of color constancy and that their response properties are thus able to reflect color perception.

Action Potentials↗
PubMed1985

Color matching throughout the work week: an industrial application of the swallowtail-difference equation.

This article considers a multilevel system problem involving color perception of individual human beings, man-machine interactions, and changing social factors. Previous research on the same system found critical differences in color matching performance over a 24-hour period, modeled by a cusp catastrophe. The hypothesis now tested is whether critical differences in group performance occur in a regular weekly cycle. Subjects were 13 color matchers and 30 printers who worked rotating shifts. Data were drawn from production records for 27 pairs of multicolor jobs performed over three four-week periods. The swallowtail hypothesis was upheld for three criteria: color matching time (R2 = .55), printing press time (R2 = .55), and printing paper conserved or wasted (R2 = .83). Job length (difficulty), time period (denoting organizational dynamics taking place), and whether the job pair occurred in the Monday-Wednesday, or Thursday-Saturday part of the week (semicycle) served as control variables.

Color Perception↗
PubMed1995

Network simulations of retinal and cortical contributions to color constancy.

A biologically-based neural network simulation is used to analyze the contributions to color perception of each of several processing steps in the visual system from the retina to cortical area V4. We consider the effects on color constancy and color induction of adaptation, spectral opponency, non-linearities including saturation and rectification, and spectrally-specific long-range inhibition. This last stage is a novel mechanism based on cells which have been described in V4. The model has been tested with simulations of several well known psychophysical color constancy and color induction experiments. We conclude from these simulations the following: (1) a simple push-pull spectrally specific contrast mechanism, using large surrounds analogous to those found in V4, is very effective in producing general color constancy and color induction behavior; (2) given some spatio-temporal averaging, receptor adaptation can also produce a degree of color constancy; (3) spectrally opponent processes have spatial frequency dependent responses to color and brightness contrast which affect the contribution of the V4 mechanism to color constancy in images with nonuniform backgrounds; and (4) the effect of the V4 mechanism depends on the difference between center and surround while the effect of adaptation depends on the total sum of inputs from both center and surround and therefore the two stages cooperate to increase the range of stimulus conditions under which color constancy can be achieved.

Adaptation, Ocular↗
PubMed1995

Rayleigh matches and unique green.

There are recurrent reports that Rayleigh matches are bimodally distributed in the colour-normal male population. Similar claims have been made for the distribution of the spectral locus of unique green. Moreover, a positive correlation has sometimes been reported between Rayleigh matches and unique green. Using a computer-controlled Maxwellian colorimeter and bias-free psychophysical methods, we measured both variables for 97 colour-normal male observers. We do not find a bimodal distribution either of Rayleight matches or of settings of unique green. Nor do we find any correlation between the two variables. However, we do observe a very significant relationship between the lightness of the subject's iris and the wavelength that he judges to be unique green.

Adaptation, Ocular↗