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PubMedDate not supplied

Color perception among different dental personnel.

This study investigated the differences in color perception among distinct groups of dental personnel. Four groups of dental personnel (10 dental technicians, 15 final-year dental students, 15 general practitioners and 10 prosthodontists) were asked to match seven test tabs of shades A1, A4, B2, B3, C2, C4 and D3 (Z100 shade guide, 3M Dental Products, St Paul, MN 55144, USA) against a standard Vita shade guide under similar lighting conditions. The results obtained were computed into L*a*b* values using a small-area colorimeter (Dental Colorimeter, Minolta Camera Pte Ltd). The data were analyzed using one-way ANOVA/post-hoc Scheffe's test at significant level p<0.05. The results showed significant differences in deltaE (color difference) between the dental technicians and the clinicians for shade C4. The significant difference that was observed in deltaE for dark shades between dental personnel was mainly contributed to a disparity in L* values. A significant difference in deltaL* was observed between dental technicians and prosthodontists for shade C4.

Analysis of Variance↗
PubMed2002

[Direct heterochromatic comparison for color perception evaluation].

We analyzed the data obtained from the Malbrel chromatometer, a device that examines color vision. The principle of the chromatometer is based on the opponent chromatic receptive fields of the retina. It shows two adjacent luminous windows of small size that can be either red and green or yellow and blue. The patient's task is to adjust the brightness of the red window (or the yellow window) to a fixed green (or blue) window luminance. Several luminance levels were studied and data were recorded using specific software. The luminance and the chromatic coordinates of the windows have been determined. The aim of the statistical study was to compare the data with a simple distribution law and therefore to know if the chromatometre allows measurement of color vision. In this investigation, 95 eyes were studied. Each patient has to match 4 red/green brightness levels and 4 yellow/blue brightness levels. The main characteristics were evaluated: the means, medians and standard deviations. Then, from the qq-plots we verified that the data distribution was near normal distribution. The percentile curves allowed 3 types of color vision to be determined. Around the median normal color vision can be defined. Between the 10(th) and the 20(th) percentiles and between the 80(th) and the 90(th) percentiles, a small anomaly was present. Below the 10(th) percentile or above the 90(th) percentile, a substantial anomaly was present.

Adult↗
PubMed2002

Color perception is mediated by a plastic neural mechanism that is adjustable in adults.

An intensely debated issue concerning visual-experience-dependent neural plasticity is whether experience is required only to maintain function or whether information from experience is used actively, relieving the necessity to hard-wire all connections and allowing adaptive adjustments. Here, an active role for experience is demonstrated in circuits for color vision. Chromatic experience was altered using colored filters. Over days there was a shift in color perception, as measured by the wavelength of unique yellow, which persisted 1-2 weeks after the filters were discontinued. Moreover, color-deficient adults were shown to have altered weightings of inputs to chromatic channels, demonstrating a large neural adjustment to their inherited photopigment defect. Thus, a neural normalization mechanism for color perception, determined by visual experience, operates to compensate for large genetic differences in retinal architecture and for changes in chromatic environment.

Adaptation, Physiological↗
PubMed2001

Illuminant cues in surface color perception: tests of three candidate cues.

Many recent computational models of surface color perception presuppose information about illumination in scenes. The models differ primarily in the physical process each makes use of as a cue to the illuminant. We evaluated whether the human visual system makes use of any of three of the following candidate illuminant cues: (1) specular highlight, (2) full surface specularity [Lee, H. C. (1986). Method for computing the scene-illuminant chromaticity from specular highlights. Journal of the Optical Society of America A, 3(10), 1694-1699; D'Zmura, M., & Lennie, P. (1986). Mechanisms of color constancy. Journal of the Optical Society of America A, 3(10), 1662-1672], and (3) uniform background. Observers viewed simulated scenes binocularly in a computer-controlled Wheatstone stereoscope. All simulated scenes contained a uniform background plane perpendicular to the observer's line of sight and a small number of specular, colored spheres resting on the uniform background. Scenes were rendered under either standard illuminant D65 or standard illuminant A. Observers adjusted the color of a small, simulated test patch to appear achromatic. In a series of experiments we perturbed the illuminant color signaled by each candidate cue and looked for an influence of the changed cue on achromatic settings. We found that the specular highlight cue had a significant influence, but that the influence was asymmetric: greater when the base illuminant, CIE standard Illuminant A, was perturbed in the direction of Illuminant D65 than vice versa. Neither the full surface specularity cue nor the background cue had any observable influence. The lack of influence of the background cue is likely due to the placement of the test patch in front of the background rather than, as is typical, embedded in the background.

Color Perception↗
PubMed2002

Effects of rod activity on color perception with light adaptation.

To investigate the effect of rod activity on color perception with light adaptation, chromaticity shifts of monochromatic test lights were measured as a function of background field intensity at 17 deg in the nasal field of view. The measurements were performed both after complete dark adaptation and during the cone-plateau period at a mesopic test intensity level of 15 photopic trolands. To clarify the mechanisms underlying the chromaticity shifts obtained, six supplementary experiments were performed. The results of the experiments strongly suggest that at scotopic background intensities, light adaptation of rods, both within and adjacent to the test area, may reduce rod signals triggered by the test light and thereby produce marked chromaticity shifts with light adaptation. At mesopic background intensities, cones in the background field become activated and may influence the chromaticity shift with light adaptation both by suppressing signals from rods elicited by the test light and by producing a selective chromatic adaptation.

Adaptation, Physiological↗
PubMed1992

Cerebral lateralization and color perception: a transcranial Doppler study.

Eight normal subjects were examined in dark, light and color conditions. Mean cerebral blood flow velocity (MBFV) were recorded almost simultaneously from their posterior cerebral arteries (PCA) using transcranial Doppler (TCD) ultrasound. The side-to-side difference was significant during the dark (p = 0.0159) and color stimulation (p = 0.0001) but not in light condition. This side-to-side difference in MBFV was used to characterize lateralization of color perception. This showed that the right PCA was always greater than the left during the presentation of color stimuli. Primary psychological colors (blue, yellow, red and green) induced greater lateralization as compared with color resulting from a mixed blue-green wavelength. This suggests that the right visual cortex is selectively sensitive to wavelengths.

Adolescent↗