The effects of psychophysical procedure and stimulus duration in the measurement of Bezold-Brücke hue shifts.
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Color Perception↗
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Induced desensitization.
Viewing of annuli modulated in color in a sawtooth fashion in time results in differential threshold elevations for the detection of color changes of inscribed disks. The elevations are of nearly the same magnitude as those resulting from viewing modulated disks. However, the differential effects on thresholds for complimentary colors are reversed. The differential effects, thus, are correlated with the variation in appearance of the test area.
Color Perception↗
Additivity of yellow chromatic valence.
The additivity of yellow chromatic valence was investigated by the hue cancellation method for two normal observers. Additivity held in 530-550 nm and 600-630 nm pairs, while additivity failure of reduction type occurred in 530-570 nm pair for both observers. Additivity failure of enhancement type occurred in 530-600 and 530-630 nm pairs in which one observer showed reduction type failure when mixture ratio of 530 nm is greater than 600 or 630 nm. The results suggest a nonlinear property of the yellow-blue process and are discussed in an interaction between the two opponent processes.
Color Perception↗
A comparative study of successive and simultaneous methods in colour discrimination.
Simultaneous and successive methods of comparison of stimuli are studied by comparing experimental results of colour discrimination experiments. In this way, colour differential thresholds for two normal observers and four different stimuli were measured by the two methods. In most cases, the capacity to discriminate colour decreased when the successive method was used, although no differences were found in qualitative aspects of discrimination. These results differ somewhat from previous reports in this field, probably because of experimental differences in the method of obtaining the thresholds.
Color Perception↗
Temporal induction of blackness--I. Color appearance.
Three color-normal observers described the appearance of colors under conditions of temporal induction. One of four inducing fields (unique blue, unique green, unique yellow, unique white) was foveally viewed for 5 sec followed immediately by a 400 msec reference stimulus of the same size (0.75 deg) and spatial location as the inducing field. The reference stimulus was 3 or 5 td and appeared achromatic to the observer when viewed without the inducing field. After presentation of this temporal sequence, the observers described the reference stimulus by assigning percentages to the terms red, green, yellow, blue, white and black. The range of inducing field intensities was -0.4-3.2 log td. Both chromatic and achromatic induction occurred at low illuminance levels of the inducing fields. As the illuminance of the inducing field increased, the reference stimulus gradually became blacker and the chromatic components less prominent. The minimum illuminance level at which the reference appeared 100% black was the same for the four different inducing fields.
Adult↗
Do deviations from radiance-invariance of metameric matches contradict the three pigment theory of foveal trichromacy?
According to the pigment theory of matching, metameric matches result from the equation of the rates of photoisomerizations for each of the three classes of cone pigments excited by the two matched fields. If true, matches are radiance-invariant and additive. Tests of the theory in this paper show small but ubiquitous failures in radiance-invariance due to systematic rather than random errors in matching. A choice between two possible explanations for these systematic errors favors the view that in subjects who deliberately or intuitively search for the middle of the matching range, the errors are due to an asymmetry in the Weber fraction for color (Trezona) at low (but not high) levels of retinal illuminance.
Analysis of Variance↗
Foveal cone detection statistics in color-normals and dichromats.
We measured for six male observers, the psychometric functions for the detection of two simultaneously presented points of light. The test stimuli were two 1 min point sources separated by 17 min arc, and pulsed for 0.5 msec. The stimuli varied in wavelength from 500 to 620 nm. The psychometric functions were fit with a model that assumes ideal detection and the following properties: (1) Poisson-distributed quantal absorptions; (2) binomial sampling of foveal long-wavelength-sensitive (LWS) and middle-wavelength-sensitive (MWS) cones; (3) independent responses of the LWS and MWS cones; and (4) the Smith-Pokorny fundamentals for cone spectral sensitivities. Based on chi 2 fits to the psychometric functions for detecting neither, one or both of the two-point stimuli presented, estimates were derived for the minimum quantal catch by a single cone for detection (C), the number of effective cones illuminated by a point stimulus at threshold (N) and the proportion of central foveal cones of the LWS type (PL). Three observers were color-normal, two were protanopes and one was a deuteranope. A second deuteranope was included in the design but his data were too unreliable for an unambiguous solution. The estimated quantal requirement C was consistently near 5(4-6), and the effective number of illuminated cones always was 1 or 2. The plausible range of PL (98% confidence interval) for the color-normal observers was 0.48-0.68 (observer YY), 0.76-0.90 (observer MW) and 0.77-0.95 (observer DF). The best fitting PL solution for these observers were 0.61, 0.82 and 0.88, respectively. These were comparable to the values obtained from flicker photometric data. The best PL value for each of the protanopes was 0.00 and for the deuteranope the best PL value was 0.98.
Color Perception↗
Changes in pattern induced flicker colors are mediated by the blue-yellow opponent process.
The colors of Benham's Top [pattern induced flicker colors (PIFCs)] were matched with color stimuli provided by a computer aided color mixer. Subjects viewed a series of specifically modified black and white disks and matched the resulting subjective color with a comparison field containing the color generated by additive mixing. Different phase relations between the apparently colored ring and the surround were tested. The color loci of all PIFCs were found to lie on a plane in receptor three-space which is given by the axis of the shortwave receptor excitation and a vector given by combining the middle and long wave receptor excitation directions in a fixed ratio of nearly 1:1. From the orientation of this plane it can be deduced that the blue-yellow opponent process (the blue-on-center cells) alone accounts for the different PIFCs.
Adult↗
Color discrimination and adaptation.
We have measured color discrimination in the isoluminant plane under rigorously controlled adaptation conditions. Two regimes were studied. Under the first regime the observer was adapted to the region of color space in which the discriminations were made. Thresholds for detecting changes along the S-(L + M) axis are a linearly increasing function of the excitation of the S cones. Thresholds for detecting changes along the L-M axis are independent of the locus of adaptation along this axis. The straightness of these functions is inconsistent with the theory that second stage mechanisms are more sensitive in the middle of their operating ranges. No convincing evidence of interactions in the effects of adaptation locus or test stimuli was observed. Under the second regime the observer was adapted to one point in color space and the stimuli to be discriminated were located in other places in color space. Discrimination seems to be limited primarily by mechanisms maximally sensitive to modulation along the isoluminant cardinal axes but evidence suggestive of the operation of higher order mechanisms was also found.
Adaptation, Ocular↗
Reversal in the sequence of the Benham colours with a change in the wavelength of illumination.
A Benham disk was rotated at 7 c/sec and illuminated by monochromatic lights from the range 534-586 nm. The elicited colours of the rings were described either with a colour naming procedure or by matching with a Munsell chip. Exchanges of hues between the two extreme rings and between the two inner rings were reported around 557 and 566 nm by the colour naming procedure, thus resulting in a hue reversal in the spatial display of colours. Similar hue shifts were also reported with the matching procedure. The effect of a possible displacement in the equilibrium of colour-opponent cell population, resulting from chromatic adaptation, is discussed.
Adaptation, Ocular↗
Methodology-specific Rayleigh-match distributions.
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Adolescent↗
Systematic measurement of human neonatal color vision.
We used a new time-efficient method to evaluate chromatic-achromatic discrimination in newborn (n = 36) and 1-month-old (n = 34) human infants. Results showed that 74% of newborns discriminated a 10.5 x 17.5 deg broadband red patch from all relative luminances of an achromatic background, but only 14% of newborns did so with a blue, 36% with a green, and 25% with a yellow patch. Most infants who "failed" did so at relative luminances very close to the respective photopic luminance match. At 1 month, performance improved somewhat although infants still show clear evidence of discriminating only the red patch. These results, the first to be obtained from individual newborns with a method incorporating a systematic variation of luminance, imply that early color vision is very limited. Possible photoreceptoral and neural bases for these immaturities are discussed.
Child Development↗
A new interference score for the Stroop test.
A New interference calculation method for the Stroop test was developed based upon a neuropsychological model of the suppression of word reading in favor of color naming. Polynomial regression equations show a significant relationship between word reading and the New interference score that closely fits the underlying prediction of the New model, while the Golden [Stroop Color and Word Test, Stoelting Co., IL, Wood Dale, 1978] model (Old) produces only a random relationship. Constructs of developmental maturation and lateralized brain damage are supported by the New but not the Old method. The New compared to the Old method also gives a significant reduction in scores in a small sample of demented patients. It would be advisable to use this New model in both cognitive and neuropsychological comparisons of different lesions or different stimulus and response demands. The New model will also help promote finer clinical inferences when an understanding relative to the patient's own baselines is necessary.
Adolescent↗
The effect of decreased visual acuity on clinical color vision testing.
PURPOSE: Evaluate the effect of visual acuity on color vision testing. DESIGN: University based clinical experimental study. METHODS: Right eyes of 12 healthy subjects were fogged with plus lenses to logMAR 1.88 and assessed with D-15 panel, Ishihara, and Hardy-Rand-Rittler (HRR) plates. Subjects were tested at lesser degrees of fogging, 0.1 logMAR intervals. The acuity at which 5% of the population tests abnormally was estimated as follows. The average acuity at which a 10% reduction in correct responses occurred was determined. From this, two standard deviations were subtracted. Examination devices were compared using repeated measures analysis of variance. RESULTS: Color vision testing did not significantly differ from baseline up to logMAR 1.40 (D-15 panel), 1.10 (HRR plates), and 0.72 (Ishihara plates). Testing devices were significantly different (P < .005). CONCLUSIONS: Color vision testing is accurate up to logMAR 1.40 (20/501) with D-15 panel, 1.10 (20/252) with HRR plates, and 0.72 (20/106) with Ishihara plates.
Adult↗
Transcaruncular orbital decompression: an alternate procedure for Graves ophthalmopathy with compressive optic neuropathy.
PURPOSE: To study the efficacy of transcaruncular orbital apex decompression for Graves ophthalmopathy with compressive optic neuropathy nonresponsive to pulse corticosteroids. DESIGN: Retrospective, interventional case series study. METHODS: From August 1999 to November 2003, transcaruncular orbital decompression was performed in 22 consecutive Graves ophthalmopathy patients with compressive optic neuropathy refractory to pulse corticosteroids. The average period of corticosteroid treatment was 16.1 +/- 5.2 days. Main outcome measures were preoperative and postoperative best-corrected vision, Hertel exophthalmometry, 100-hue color sensation test, visual evoked potential, visual field, and new-onset diplopia. RESULTS: Visual acuity improved significantly from 1.08 +/- 0.24 logarithm of minimal angle of resolution (logMAR) preoperatively to 0.29 +/- 0.18 logMAR postoperatively (P < .0001). Average improvement in retinal sensitivity was 9.4 +/- 8.2 dB, in P(100) value of visual evoked potential was 27.5 +/- 20.1, and in "total errors" of the 100-hue test was 309.9 +/- 214.3 after surgery. Average retroplacement effect was 3.7 +/- 1.6 mm. Statistical analysis showed significant differences between preoperative and postoperative measurements for all above parameters (P < .0001). New-onset diplopia occurred in 38% of patients. There were no complications specifically attributable to the transcaruncular technique. CONCLUSIONS: The transcaruncular approach offers access to the medial and inferior wall for orbital apex decompression in Graves ophthalmopathy patients with compressive optic neuropathy refractory to pulse corticosteroids. Advantages over other approaches included no external scar, less damage to adjacent tissue, and wide exposure to the entire medial wall.
Adult↗
Transcaruncular orbital decompression: an alternative procedure for graves ophthalmopathy with compressive optic neuropathy.
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Color Perception↗
Colour vision and occupational toluene exposure: results of repeated examinations.
Potential effects of human occupational exposures to toluene on colour vision were investigated in a follow-up study over 4 years with three repeated examinations. Colour vision was measured with the Lanthony desaturated colour vision test D-15d, and the colour confusion index (CCI) was calculated. The mean current exposures were 26+/-21 ppm for printers (high toluene level) and 3+/-4 ppm for end-processors (low toluene level). The mean exposure durations were 23+/-6 years for "long-time exposed" and 7+/-2 years for "short-time exposed" subjects. Repeated analyses (n=162) and multiple regressions (maximum available n=267) did not reveal significant effects of toluene with respect to intensity or duration of current or long-term exposure. Age and occupational qualification were significantly associated with CCI in both kinds of analysis, whereas alcohol consumption (carbohydrate-deficient transferrin, CDT) and smoking habits (cigarettes per day) were not. It is concluded that current industrial exposure limits of toluene provide sufficient protection against possible disturbance of colour vision.
Adult↗
Associating color appearance with the cone chromaticity space.
A cone chromaticity space, a transform of a colorimetric specification system into coordinates that represent cone excitations, does not provide color appearance information. Boynton and Olson (Color Research and Application 12, 94-105, 1987) gathered color naming for the 424 Optical Society of America Uniform Color Scales (OSA-UCS) color samples. Here, a computational algorithm was developed that converts OSA-UCS sample values into L, M, S cone excitations based on the 1964 CIE 10 degrees Standard Observer. This makes it possible to plot the cone chromaticities associated with the eight color names used by Boynton and Olsen's observers to describe the non-dark appearing colors.
Algorithms↗