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PubMed1992

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↗
PubMed1992

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↗
PubMed1994

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↗
PubMed2002

A double-blind placebo-controlled evaluation of the acute effects of sildenafil citrate (Viagra) on visual function in subjects with early-stage age-related macular degeneration.

PURPOSE: To assess the effects of a single 100-mg dose of sildenafil citrate on visual function in men with early-stage age-related macular degeneration. DESIGN: Randomized double-blind placebo-controlled clinical trial. METHODS: Nine men (mean age 71 years, range 59-85 years) with early-stage (minimal visual impairment and large drusen in the macula) age-related macular degeneration and 20/40 or better-corrected visual acuity in at least one eye were prospectively randomized to receive either placebo or sildenafil citrate (Viagra; Pfizer Inc, New York, New York) 100 mg as a single oral dose. After 7-14 days, they received the alternate treatment. Subjects underwent visual acuity, Amsler grid, color discrimination (D15), traffic light, Humphrey perimetry, and photo-stress testing in each eye before and at specific intervals within 8 hours after dosing. RESULTS: Compared with placebo, no pattern of errors were evident in any visual function test following sildenafil administration. No statistically or clinically relevant changes from baseline were observed in visual acuity, Humphrey perimetry (corrected pattern standard deviation), D15 color discrimination, or photo-stress tests. No clinically relevant changes were observed in the Amsler grid or traffic light tests. Sildenafil treatment was associated with transient mild or moderate headache, flushing, and rhinitis. There were no visual adverse events spontaneously reported to the investigator. CONCLUSION: A single 100-mg dose of sildenafil was well tolerated and produced no acute visual effects or exacerbation of preexisting visual impairment in nine men with early-stage age-related macular degeneration.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1978

Acquired color vision defects in retrobulbar neuritis.

We used the Farnsworth-Munsell 100 Hue Test to study the incidence of acquired color vision defects in 16 patients with unilateral and and seven patients with bilateral retrobulbar optic neuritis whose visual acuity had recovered to 6/12 (20/40) or better. We recorded the visual-evoked response to a pattern stimulus on the same day. All 30 affected eyes showed an excessive number of errors on Farnsworth-Munsell 100 Hue testing. The number of errors increased with greater residual optic nerve damage. One false-positive and two false-negative visual-evoked responses were found.

Adult↗
PubMed1998

Ishihara color plates as a test for simultanagnosia.

PURPOSE: To alert ophthalmologists to the use of Ishihara color plates in the detection of simultanagnosia. METHODS: We examined seven patients referred for impaired vision. Evaluation included color plate testing with Ishihara color plates. RESULTS: All seven patients had simultanagnosia, with marked difficulty in identifying the numbers in Ishihara color plates despite adequate visual acuity and the ability to name all of the colors in the plates correctly. One of these patients was referred with the diagnosis of a cone dystrophy because of her poor performance on the Ishihara test. All of the patients had bilateral occipitoparietal damage or atrophy on magnetic resonance imaging. CONCLUSIONS: Ophthalmologists must be aware that a poor performance with Ishihara plates may not be attributable to an impairment of color vision but rather to occipitoparietal brain damage associated with simultanagnosia.

Agnosia↗
PubMed1995

Psychophysical tests in X-linked retinitis pigmentosa carrier status.

Psychophysical tests were performed in 22 normal women and 17 X-linked carriers of retinitis pigmentosa. The tests consisted of luminance contrast sensitivity, grating at the fovea and broken annulus at the periphery, color contrast sensitivity, letters for the fovea and broken annulus for the periphery, along the three known confusion axes of protan, deutan and tritan observers. Statistical analysis of the data shows that there were significant differences between the carriers and age-similar normal subjects with all the tests. The most significant differences (P < 0.001) were found with the color contrast sensitivity at the periphery along the protanopic and deutanopic axes and the luminance contrast sensitivity at the periphery. The influence of the age is discussed.

Adolescent↗
PubMed2003

Chromatic induction and the layout of colours within a complex scene.

A target's apparent colour is influenced by the colours in its surrounding. If the surrounding consists of a single coloured surface, the influence is a shift 'away' from the surface's colour. If the surface is more than 1 degrees from the target area the shift is very small. If there are many surfaces, then not only the average luminance and chromaticity of the surfaces matters, but also the chromatic variability. It is not yet clear whether it makes any difference where the chromatic variability is within the scene, so we constructed stimuli in which the chromatic variability was restricted to certain regions. We found that it made very little difference where the chromatic variability was located. The extent to which the average colour of nearby surfaces influences the apparent colour of the target seems to depend on the average chromatic variability of the whole scene.

Color Perception↗
PubMed1998

Colour discrimination thresholds in Parkinson's disease: results obtained with a rapid computer-controlled colour vision test.

A dysfunction of dopaminergic retinal neurons is thought to occur in Parkinson's disease, manifesting itself in impaired performance on various visual discrimination tasks. We have investigated whether differences in colour discrimination could readily be detected between a normal group and a Parkinsonian group, using a computer-controlled test of colour vision. Although some individual Parkinsonian patients showed an abnormal elevation of colour discrimination thresholds, there was no significant difference between the normal group and the Parkinsonian group.

Age Factors↗
PubMed1998

Dependence of color on context in a case of cortical color vision deficiency.

Color constancy depends on sensitivity to change in both illumination spectral properties and object position. We investigated this latter form of color constancy by asking a cerebral achromatopsic to name the colors of papers that were presented atop black, gray or white backgrounds under identical illumination. Comparison of color names across background conditions reveals poor constancy, characterized by a contrasting of foreground and background values that is not corrected by proper anchoring.

Brain Diseases↗
PubMed1998

Colour vision in normal subjects tested by the colour arrangement test 'Roth 28-hue desaturated'.

The aim of the study was to obtain normal values for the colour-arrangement test, Roth 28-hue desaturated. In 146 healthy non-smokers colour vision was tested monocularly. The subjects were divided into four age groups: 0-19, 20-39, 40-59, and 60-79 years. The overall error score for all groups was 54 +/- 24 (median +/- mean absolute deviation). The values for the 20-39 year group were significantly lower than those for the other groups (Kruskal-Wallis: P < 0.0001 with subsequent multiple Mann-Whitney test). An increasing predominance of errors along the blue-yellow-axis was observed with increasing age. The error scores of normal subjects tested by the Roth 28-hue desaturated were comparable with those on the well-known Farnsworth-Munsell 100-hue (FM-100). Because the Roth 28-hue desaturated is shorter and simpler to administer, it is an alternative to the FM-100 in situations that need to assess colour discrimination and error axis quantitatively and quickly.

Adolescent↗
PubMed1998

Color appearance: neutral surrounds and spatial contrast.

The experimental data in this paper show that chromatic bars presented in alternation with equiluminant neutral-appearing bars are seen as more saturated than the same chromaticity presented as a uniform rectangle. This effect was diminished but not eliminated when test and match stimuli were presented within a slightly dimmer neutral surround. The test stimulus was a 2 x 5 degrees rectangle with a 0.7 cpd square wave grating composed of alternating equiluminant chromatic test bars and neutral bars. Asymmetric matching was used to match the test bar appearance to a uniform 2 x 5 degrees comparison rectangle. Test and comparison stimuli were presented to separate eyes in a haploscope and appeared flanking a central fixation target. Data were collected with test and inducing stimuli on the cardinal axes of color space. Test bars separated by neutral bars appeared more saturated than the comparison rectangle for both the l- and s-axis directions. Manipulation of excitation on one cardinal axis did not affect the appearance matches made for the other cardinal axis.

Adult↗
PubMed1998

Colour vision in gyrate atrophy.

A follow-up study of colour vision in two patients with gyrate atrophy was performed. Gyrate atrophy was diagnosed in the first patient at the age of 17 years. Her colour vision was first tested at the age of 25 years; at the follow-up examination 7 years later, she correctly interpreted the Standard Pseudoisochromatic Plates part 2, however, with one mistake due to lens opacity. In the Farnsworth-Munsell 100 hue test and in the Color Vision Meter 712 (CVM) anomaloscope, the results were within normal ranges. In the second patient, gyrate atrophy was diagnosed at the age of 4 years. At the ages of 4 and 5 years, he correctly interpreted the Ishihara, AO H-R-R, and Lanthony Tritan Album plates as well as the City University test. At the ages of 6, 7, and 8 years, he correctly interpreted the plate tests, the Farnsworth Panel D 15, and Lanthony's Desaturated Panel. The CVM anomaloscope results were normal.

Adult↗
PubMed1998

Recent evolution of uniform trichromacy in a New World monkey.

Until recently, New World primates were found to have a single M/L photopigment gene on the X-chromosome. This arrangement limits males to dichromatic, or monochromatic color vision. Only females who were heterozygous for the M/L gene were trichromatic. Recently, an exception has been discovered. Male howler monkeys appear to have more than one M/L pigment gene, and both genders are uniformly trichromatic. We characterized promoter regions corresponding to two M/L pigment genes in howlers. Comparison of DNA sequences with those of humans and three species of New World primate suggest a recent and independent acquisition of a second M/L gene locus in the howler.

Animals↗
PubMed1999

The oblique effect with colour defined motion throughout the visual field.

We assessed the extent of the oblique effect (OE) and the meridional orientation effect (MOE) for a chromatic motion task using red/green gratings throughout an 80 degrees visual field. Four different stimulus orientations were tested. Generally, sensitivity to chromatic motion decreased with increasing eccentricity regardless of the visual field meridian. Also, sensitivity was highest for horizontal or vertical gratings, thus supporting the presence of an OE rather than of a MOE. The strength of the OE varied between subjects, but was present from the fovea to 20 degrees of eccentricity. At 40 degrees of eccentricity, chromatic motion was always perceived but the grating orientation did not consistently influence chromatic motion sensitivity. The present study confirmed our previous results on chromatic motion sensitivity and isoluminance ratios throughout the visual field. In addition, our data show that the chromatic system can exhibit OEs at lower spatial frequencies than is observed for the achromatic system.

Analysis of Variance↗