Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Color Vision Defects”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73Linked to original sources
PubMed1989

Differences in the responses of heterozygous carriers of colorblindness and normal controls to briefly presented stimuli.

Two experiments were conducted in order to investigate the possible effects of X-inactivation (Lyon, 1961) on female carriers of colorblindness. The results of the first experiment, like those of Grützner et al. (1976), were consistent with the prediction of the Lyon (1961) hypothesis that the retinas of female carriers are composed of mosaic patches of colorblind and normal areas. In this first experiment, rows and columns of colored spots were presented tachistoscopically, and subjects were asked to identify the colors of the spots. In the second experiment, plates from the Ishihara test of colorblindness were presented tachistoscopically and subjects were asked to identify the number which was embedded in the pattern of colored dots. Both experiments support the Lyon hypothesis in that female carriers were found to have more difficulty in perceiving patterns of colored stimuli than did control subjects, and they suggest that the amount of time that a carrier has to scan colored stimuli plays an important role in her ability to accurately perceive them.

Color Perception↗
PubMed1989

The density of cones in the fovea centralis of the human dichromat.

We present estimates, based on psychophysical measurements, of the density of cones in the fovea centralis of human dichromats. The estimates for a group of three protanopes and three deuteranopes (this study) were compared to the estimates of the density of cones in a group of six color normal trichromats from previous studies (Cicerone & Nerger, 1985, 1989). The results support the conclusion that the density of cones in the fovea centralis of the dichromat is comparable to that of the color normal trichomat. These results tend not to support a model of dichromacy in which a class of cones as well as the associated pigment are lost in the dichromatic eye. Instead, dichromacy appears to involve a loss of one of the three visual pigments associated with human trichromacy, with a retention of the full numbers of cones.

Cell Count↗
PubMed1990

Discrimination of luminance and chromaticity differences by dichromatic and trichromatic monkeys.

Dichromatic and trichromatic representatives from two genera of platyrrhine monkeys that show widespread color vision polymorphism (Saguinus--tamarins, Saimiri--squirrel monkeys) were tested for their abilities to make increment-threshold and flicker discriminations based on luminance and chromaticity differences. The details of these tests were arranged to attempt to emphasize the relative contributions to visual behavior of non-opponent and spectrally-opponent neural mechanisms. The results indicate that dichromatic and trichromatic monkeys differ only trivially on tests where performance is based on the contributions of non-opponent mechanisms, that the contribution of spectrally opponent mechanisms to the "brightness signal" is very similar in trichromatic and dichromatic monkeys, and that in increment-threshold discriminations where there are both chromaticity and luminance cues some test wavelengths yield superior performance for trichromats while others appear to favor the dichromat.

Animals↗
PubMed1990

LWS cone effects on rod threshold and saturation in achromats with residual cone function.

Rod saturation on flashed and steady red backgrounds was investigated in normals and three achromats, two of whom were found to have some residual cone function. LWS cones selectively reduce the background level at which rod saturation occurs and elevate rod thresholds at flashed background levels well below saturation. Both of these LWS cone actions are also present in eyes with greatly reduced LWS cone function. In normal eyes LWS cones also elevate rod thresholds on steady backgrounds. We thus conclude that LWS cones influence rods through different mechanisms under transient (flashed) and steady-state background stimulation and that the increase in rod visual sensitivity observed during prolonged presentation of a background is due to a time-dependent reduction of LWS cone influence on rods. Finally, the finding that rod-cone interactions of the same magnitude found in normals can be seen in individuals where the cones' ability to mediate vision is severely reduced suggests the rod saturation paradigm as a sensitive technique for revealing residual LWS cone function.

Adaptation, Ocular↗
PubMed1991

Color vision following intense green light exposure: data and a model.

Hue discrimination, spectral sensitivity, and mathematical models of both are presented for a rhesus monkey which was exposed to intense green light. One of the monkey's eyes was blue-blinded in a previous experimental procedure and the other was color normal. The results of green light exposure showed a loss of sensitivity on both measures, with greater loss in the blue-blinded eye. Although there was considerable loss of hue-discrimination in the blue-green spectral regions, hue-discrimination at the point of best discrimination, 590 nm, remained unaffected. This pattern of results poses difficulties for models of hue discrimination, and has resulted in the proposed model employing three opponent color channels. The number of free-parameters are minimized and the integration between spectral sensitivity and hue discrimination enhanced by deriving parameters used in modeling hue discrimination from spectral sensitivity or vice versa.

Animals↗
PubMed1991

Induced color blindness in goldfish: a behavioral and electrophysiological study.

To answer the question whether, like man, ethambutol treated fish would become color-blind, wavelength discrimination was measured behaviorally in goldfish, preceding, during and after ethambutol treatment. The results are that of the three high discrimination abilities at around 400, 500 and 600 nm, ethambutol affected the latter one. Red-green discrimination is lost reversibly leaving the discriminations in the blue-green and violet range unaffected. This red-green discrimination deficiency cannot be accounted for by a loss of long wavelength cones since the ERG and luminosity functions remain unaffected. Intracellular horizontal cell recordings in goldfish show that ethambutol hyperpolarizes all three types of cone driven horizontal cells and changes their color coding such that their spectral characteristics become cone-like as is the case in dark adapted retina. So, the initial effect induced by ethambutol seems to be an adaptation deficiency in color vision related tasks. Human wavelength discrimination and increment threshold spectral sensitivity functions obtained at low luminance levels are compared to behavioral functions in ethambutol treated goldfish. The high similarity between the ethambutol effects in man and goldfish, and the effects observed in the horizontal cell responses in goldfish are highly indicative that horizontal cells play a key role in color vision. So far their function has been puzzling.

Animals↗
PubMed1991

Nonlinear distortion of gratings at the foveal resolution limit.

Aliasing by the foveal cone mosaic causes high frequency interference fringes to look like bright and dark zebra stripes (primary zebra stripes) [Williams, Vision Research, 25, 195 (1985); Vision Research, 28, 433 (1988)]. Some observers report another type of zebra stripes defined by variations in chromaticity as well as brightness, which we call secondary zebra stripes. The conditions required to see the secondary zebra stripes are almost identical to those required to see the primary zebra stripes, except that they are seen at approximately half the spatial frequency. We consider the hypothesis that the secondary zebra stripes arise from aliasing by a particular packing arrangement of the M and L cone submosaics, but present evidence favoring an alternative hypothesis based on a known local nonlinearity in the visual system.

Color Vision Defects↗
PubMed1991

Bicuculline produces reversible red-green color blindness in goldfish, as revealed by monocular behavioral testing.

The effect of the GABAA receptor antagonist bicuculline (methiodide) on goldfish wavelength discrimination was studied. This was done using a behavioral two alternative forced choice procedure at training wavelengths 500 and 600 nm, where goldfish wavelength discrimination is the best. During the experiments the goldfish could use only the eye that was intravitreally injected with bicuculline; the other eye was covered. In control experiments, to exclude systemic effects, the covering of the eyes was reversed. Bicuculline induced loss of wavelength discrimination ability around 600 nm, while this ability was not affected around 500 nm. The effect was reversible, since discrimination around 600 nm returned to normal within a day after injection. The results indicate that GABAA receptor mediated processes, like horizontal cell to cone feedback, play an important role in wavelength discrimination at the long wavelength part of the spectrum.

Animals↗
PubMed1991

The contribution of color to motion in normal and color-deficient observers.

By opposing drifting luminance and color gratings, we have measured the "equivalent luminance contrast" of color, the contribution that color makes to motion. We found that this equivalent contrast was highest (greater than 10%) for low spatial and temporal frequencies and was higher for red/green than for blue/yellow stimuli. Equivalent luminance contrast was about 4% for a green/purple stimulus that fell along the tritan confusion line, indicating a modest input to the motion pathway from the short wavelength-sensitive cones (B-cones). Contrast thresholds for the discrimination of the direction of motion showed that the contribution of color to motion was about the same (within a factor of 2) as that for luminance in terms of multiples of threshold contrast. These responses to moving, chromatic gratings could be mediated by any of several factors that can create a residual response in a luminance pathway: temporal phase lag between the responses to the colors of the stimuli, second harmonic distortion in the response and variability in equiluminance points across units. Each of these factors was evaluated experimentally and their combined effect could account for only a small portion of the contribution of color to motion. As a result, we attribute the perception of the motion of equiluminous stimuli to an opponent-color input to directionally selective cortical units. Chromatic stimuli had little or no equivalent contrast for color-deficient observers, whether the stimulus was red/green, which they discriminate less well than normals, or blue/yellow, which they discriminate almost as well as normals. The equivalent contrast measure provided an excellent basis for classifying normal, protan and deutan observers.

Color↗
PubMed1992

Effects of colour substitutions upon motion detection in spatially random patterns.

To investigate the effects of colour upon motion detection, the short-range motion displacement limit (Dmax) was determined using two-frame kinematograms in which the two classes of square comprising the pattern differed both in luminance and in colour. In the second motion frame, the squares retained either the same luminance and colour as in the first frame, or they changed their colour while retaining their luminance. The experiment was repeated at three different viewing distances to investigate the effects of element angular size. Two of the four observers had normal trichromatic colour vision; the other two were dichromats (protanopes). For the trichromatic observers, the change of colour between frames made motion displacements harder to detect when the squares were large, but not when they were small. The result accords with an input of colour into motion detection at low but not at high spatial frequencies. For the dichromats, the colour change had little effect at any of the viewing distances, thus ruling out the possibility that the deleterious effects of colour substitution upon motion detection in trichromats was due to chromatic aberration or other artefacts.

Color Perception↗
PubMed1992

Spectral sensitivities for illusory contour perception: a manifold linkage of chromatic and achromatic cues with the generation of contours.

Using colored inducing patterns presented as increments upon a white uniform background, the increment thresholds needed for illusory contour perception were measured as a function of the wavelength of inducing pattern. The spectral sensitivity functions were obtained with varying adaptation level and stimulus configuration, high and low background illumination, and line-based and figure-based inducing patterns. The results showed a distinctive feature between the line-based and the figure-based illusory contours. The sensitivity functions for the line-based illusory contours showed the characteristics of non-opponent mechanisms and they were shape invariant with background intensity and spatial variables. On the other hand, the sensitivity functions for the figure-based illusory contours showed non-opponent nature for low background illumination but opponent nature for high background illumination. It is suggested that the generation of illusory contours involves concurrent processing of different cues of luminance and color, and that photopic adaptation level and stimulus configuration control the degree of the contributions of chromatic and achromatic mechanisms to contour formation.

Adaptation, Ocular↗
PubMed1992

Brightness, discriminability and the "crispening effect".

Subjects adjusted the luminances, L, of 16 or 25 circles, all visible at the same time on a computer monitor, to make equal-interval brightness series. The background was black, white or grey. The luminance steps between adjacent circles behaved like the luminance discrimination thresholds of Whittle, P. [(1986) Vision Research, 26, 1677-1691)]. They showed a sharp minimum at the background luminance, Lb: the "Crispening Effect". They followed Weber's Law with respect to L when L was small, but with respect to delta L (= magnitude of L-Lb) near Lb. The Crispening Effect was abolished by a thin outline or a hue difference between circles and background.

Color Perception↗
PubMed1992

Retinal and cortical activity in human subjects during color flicker fusion.

Pattern electroretinograms (PERG) and cortical visually evoked potentials (VEP) were simultaneously recorded from 7 visually normal and 1 protanopic subjects. Stimuli were color checkerboards (0.5 degrees check size), phase-reversing at 17 Hz (i.e. 34 reversals/sec). Using a stepwise sweep procedure, the luminance of the red (lambda peak = 550 nm) and green (lambda peak = 630 nm) checks varied in 11 steps in opposite directions from 0 to 30 cd/m2, embracing the subjective equiluminance point. For normal subjects at subjective equiluminance, the VEP amplitude dropped sharply down to 13 +/- 2% of the value at pure luminance contrast. The PERG, however, was only reduced to 56 +/- 10% at this point, an attenuation 4 times less than that of the VEP. In contrast to normal subjects, in the protanopic subject the PERG was sharply reduced at equiluminance, parallel to the VEP. This would be expected when L-cones are missing. Assuming that the PERG reflects the activity of the retinal ganglion cells, our findings suggest that human retinal ganglion cells respond well under the condition of equiluminant flicker fusion, which is in agreement with recent single-cell studies in the monkey. Consequently, the temporal low-pass filter, which mediates color-flicker fusion, would seem to lie central to the retinal ganglion cells.

Adult↗
PubMed1992

Sawtooth contrast sensitivity: effects of mean illuminance and low temporal frequencies.

Temporal contrast sensitivity was measured for mirror-image sawtooth (rapid-on and rapid-off) and sine waveforms for a 1.8 deg foveal target. In one experiment, contrast sensitivity was measured for 2-26 Hz stimuli at target mean illuminance levels of 5-1260 td. At 5 td, contrast sensitivity functions for sawtooth and sine waveforms, expressed in terms of the Fourier fundamental amplitude, are equivalent. At higher light levels, sawtooth sensitivity increasingly exceeds sine sensitivity and rapid-off (decremental) sawtooths show progressively greater sensitivity than rapid-on (incremental) sawtooths. This pattern of results was obtained for two color-normal observers and for a deuteranopic observer. In a second experiment, sawtooth and sine sensitivity was tested at 500 td with an extended low-frequency range, to 0.5 Hz. Rapid-off and rapid-on sensitivities declined only slightly at low temporal frequencies in contrast with sine sensitivity. To interpret our data, we evaluate two single-pathway models (last-stage asymmetric detector and compressive response-intensity non-linearity) and a dual-pathway model in which incremental and decremental waveforms are detected by separate ON and OFF visual mechanisms.

Adaptation, Ocular↗
PubMed1993

Serine/alanine amino acid polymorphism of the L and M cone pigments: effects on Rayleigh matches among deuteranopes, protanopes and color normal observers.

In a first experiment, groups of deuteranopes and protanopes were characterized psychophysically by the slopes of regression lines fitted to yellow intensity settings from their Rayleigh matches. In a second experiment, color normal male subjects were characterized by their 2 and 8 deg Rayleigh match points. All subjects had been previously characterized genetically by the presence of the amino acid serine or alanine at position 180 on their L cone or L/M hybrid opsins. Dichromats and color normal subjects with serine had greater sensitivity to the red primary than did those with alanine. Calculations based on psychophysical results suggest that the substitution of serine by alanine in the L cone opsin or L/M hybrid opsin produces a shift in lambda max of the expressed pigment toward shorter wavelengths by an amount varying between 2.6 and 4.3 nm, with the shifts in lambda max for the dichromats being larger than those for the color normal subjects.

Adult↗
PubMed1993

Pop-out of orientation but no pop-out of motion at isoluminance.

Line textures in which one line was orthogonally oriented to the rest were briefly presented at various colour and luminance contrasts to the background. Subjects were able to detect the single line element pre-attentively even when the texture pattern was defined only by colour, indicating that "pop-out" of orientation is achieved at isoluminance. To exclude the possibility that this result was caused by luminance artefacts, especially by chromatic aberration, we carried out two control experiments. First, we showed that subjects could not detect a single moving line in a stationary texture under comparable conditions. Secondly, we repeated the experiments with a deuteranope who was unable to detect the differently oriented target under conditions under which the normal subject still could see it.

Adult↗
PubMed1993

Does chromatic sensitivity develop more slowly than luminance sensitivity?

Chromatic sensitivity is very low in humans during the first few months of life. We examined whether low chromatic sensitivity reflects a deficiency among chromatic mechanisms or whether it is simply a manifestation of poor visual sensitivity in general. The sweep VEP was used to measure contrast sensitivity to gratings varying in the mixture of red and green components. For infants from 2 to 8 weeks of age, sensitivity to all mixtures was lower than color-normal adults' sensitivity, but infant and adult ratios of luminance/chromatic sensitivity were similar. This finding is consistent with the hypothesis that infants have functional MWS and LWS cones and the requisite post-receptor chromatic mechanisms to compare their signals.

Age Factors↗
PubMed1993

A study of women heterozygous for colour deficiencies.

We have examined the colour vision of 43 female subjects in the age range 30-59 yr of whom 31 were obligate carriers of various forms of colour deficiency and the rest were women who had no known colour-deficient relatives. In the case of all the carriers we established the phenotypes of their colour-deficient sons. As a group, carriers made significantly more errors on the Ishihara plates and showed enlarged matching ranges on the Nagel anomaloscope, but we could not replicate earlier reports of increased error scores on the Farnsworth-Munsell 100-Hue test or of systematic shifts in Rayleigh match mid-points. We did find that the colour matches of carriers of deuteranomaly were significantly displaced from those of normals in a ratio-matching task in which a mixture of 546 and 600 nm was matched with a mixture of 570 and 690 nm. Owing to X-chromosome inactivation, women who are heterozygous for anomalous trichromacy ought to have at least four types of cone in their retinae and we ask whether this affords them an extra dimension of colour vision, by analogy to New World monkeys where heterozygous females gain trichromacy in a basically dichromatic species. Many carriers of anomalous trichromacy exhibited no evidence for tetrachromacy, in that they accepted large-field Rayleigh matches following a rod bleach and they were unable to set unique matches in our ratio-matching task. However, eight carriers of anomalous trichromacy--and no other subject--refused large-field Rayleigh matches; and we found one carrier of deuteranomaly who was apparently able to make unique matches in the ratio-matching task.

Adult↗