Search results for "Color vision"
showing 10 items of 92 documents
<title>Selective filters for improvement of color discrimination</title>
2003
Colored filters have been used as possible aids for perception in case of congenital color vision abnormalities. Higher stimulation for L cones in one eye (red filter) and for M cones (green) in other eye acts as a simple method to interfere in human color vision processing. Influence on subjective and objective vision performances as binocular functions, fusion, stereopsis and color vision has been tested. Special colored glasses have been created, taking into account each subjects refraction for distance and tested for the 5 months adaption time. No negative influence on binocular functions, no changes of heterophoria and lowering in fusion ability and stereopsis have been stated due to u…
Color induction via non-opponent lateral interactions in the human retina
1992
Retinal connections causing colors in Benham's top (pattern induced flicker colors, PIFCs) are investigated by psychophysical experiments. PIFCs are still seen when stimuli to different cones are demodulated selectively, indicating the involvement of non-opponent channels. PIFCs also occur on retinal areas next to those affected by modulated stimuli; further, both monochromat and dark-adapted trichromats perceive PIFCs which are achromatic. These additional findings point to horizontal cells as neuronal mediators of modulated excitation leading to PIFCs. The unspecifity of the postulated connection with respect to cone types agrees with anatomic findings of Boycott, B. B., Hopkins, J. M. an…
Motion detection in goldfish investigated with the optomotor response is “color blind”
1996
AbstractThe action spectrum of the optomotor response in goldfish was measured to investigate which of the four cone types involved in color vision contributes to motion detection. In the dark-adapted state, the action spectrum showed a single maximum in the range of 500–520 nm, and resembled the rod spectral sensitivity function. Surprisingly, the action spectrum measured in the light-adapted state also revealed a single maximum only, located in the long wavelength range between 620 and 660 nm. A comparison with spectral sensitivity functions of the four cone types suggests that motion detection is dominated by the L-cone type. Using a two colored, “red-green” cylinder illuminated with two…
Visual fields in a chloroquine treatment
2014
Purpose: In this study, we describe contrast sensitivity losses in the visual field of a patient affected by chloroquine toxicity, measured with stimuli favoring different visual mechanisms. We have compared these results with those of other, usual clinical tests. Methods: The vision of a patient who underwent ten years of chloroquine treatment was analyzed by a battery of clinical tests: visual acuity (VA), Amsler’s grid, Farnsworth–Munsell 100-hue test, spectral domain optical coherence tomography, multifocal electroretinogram (ERG), white-on-white and red-on-white Humphrey perimetries, chromatic and achromatic contrast sensitivity perimetry tests, and fluorescein angiography. Measurement…
Psychological factors and defective colour vision
1995
In this study, involving students between 14 and 16 years old, the psychological dimensions of cognition and personality affected by red-green colour vision deficiencies were investigated. From the results of a factorial analysis it appears that the influence of colour vision abnormality on the psychological factors that we tested is always minor. Colour vision defect is correlated with such cognitive variables as spatial aptitude and visual difference perception, and with such personality variables as praxemia and submission. The weighting of the cognition and personality factors linked to colour vision abnormality, however, varies considerably and does not in any case contribute more than…
Multispectral analysis of color vision deficiency tests
2011
Color deficiency tests are usually produced by means of polygraphy technologies and help to diagnose the type and severity of the color deficiencies. Due to different factors, as lighting conditions or age of the test, standard characteristics of these tests fail, thus not allowing diagnosing unambiguously the degree of different color deficiency. Multispectral camera was used to acquire the spectral images of the Ishihara and Rabkin pseudoisochromatic plates in the visible spectrum. Spectral data was converted to cone signals, and successive mathematics applied to provide a simple simulation of the test performance. Colorimetric data of the each pixel of the test image can be calculated an…
Rayleigh Equation Anomaloscope from Commercially Available LEDs
2012
Most precise classification of CVD (color vision deficits) can be provided by using anomaloscope. Today anomaloscopes are available, which can evaluate red-green (Rayleigh) and blue-green (Moreland) color defects.DOI: http://dx.doi.org/10.5755/j01.ms.18.2.1928
Behavioural thresholds of blue tit colour vision and the effect of background chromatic complexity
2020
Vision is a vital attribute to foraging, navigation, mate selection and social signalling in animals, which often have a very different colour perception in comparison to humans. For understanding how animal colour perception works, vision models provide the smallest colour difference that animals of a given species are assumed to detect. To determine the just-noticeable-difference, or JND, vision models use Weber fractions that set discrimination thresholds of a stimulus compared to its background. However, although vision models are widely used, they rely on assumptions of Weber fractions since the exact fractions are unknown for most species. Here, we test; i) which Weber fractions in lo…
Color discrimination under mesopic conditions in cats and humans
1995
The ability to discriminate colors under various levels of mesopic illumination was studied in three cats using colored papers as stimuli and with a computer controlled training schedule. Discrimination based on brightness differences was prevented using a new method in which illuminant color was varied. The luminance threshold for color discrimination in cats was found to be 0.5 cd/m2, close to the cone threshold reported by others from ganglion cell recordings. The same experiment was carried out with human subjects and revealed a luminance threshold of 0.00042 cd/m2 for color discrimination.
The stability of color discrimination threshold determined using pseudoisochromatic test plates
2014
Congenital red-green color vision deficiency is one of the most common genetic disorders. A previously printed set of pseudoisochromatic plates (KAMS test, 2012) was created for individual discrimination threshold determination in case of mild congenital red-green color vision deficiency using neutral colors (colors confused with gray). The diagnostics of color blind subjects was performed with Richmond HRR (4th edition, 2002) test, Oculus HMC anomaloscope, and further the examination was made using the KAMS test. 4 male subjects aged 20 to 24 years old participated in the study: all of them were diagnosed with deuteranomalia. Due to the design of the plates, the threshold of every subject …