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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↗

PubMed1994

Detection of functional vision loss using the Ishihara plates.

Many techniques have been described for the detection of functional visual loss. We report four cases in which Ishihara pseudo-isochromatic colour plates gave objective evidence of functional vision loss. In all cases the patients were able to read the first test pattern (No. 12), but could not distinguish any of the following pseudo-isochromatic numbers (plates 2-17). However, they experienced no difficulty in tracing the winding lines (plates 18-24), demonstrating that they in fact had normal colour vision.

Adolescent↗

PubMed2003

Adult brightness vs. luminance as models of infant photometry: variability, biasability, and spectral characteristics for the two age groups favor the luminance model.

When infants fail to make chromatic discriminations, do the characteristics of their performance minima coincide more closely with the properties of adult luminance matches or heterochromatic brightness matches? In addition to their spectral properties, adult luminance matches are typically characterized by relatively small individual differences, whereas brightness matches are believed to be both more variable and more biasable. Two complementary experiments were carried out on adults and 8-week-old infant subjects. Both groups were tested with small (1.5 degrees to 4 degrees ) red and blue test fields of varying luminances, embedded in a white surround. In adults, heterochromatic brightness matches were measured. Individual differences spanned about 0.5 log units, and brightness matches could be biased by as much as 0.8 log units by varying the range of test field luminances. In infants, the locations of performance minima were measured. Individual differences spanned less than 0.1 log units, the mean performance minima coincided with predictions based on V10(lambda), and the location of the performance minimum was nearly unaffected by the range of test field luminances used. Thus by all three criteria, these data suggest that infants' performance minima are mediated by luminance rather than by brightness signals. To date there remains no evidence that the infant visual system computes a brightness signal.

Adult↗

PubMed1982

Pi-4: adaptation of more than one class of cone.

The Pi-4 color mechanism was isolated in three observers with a 500-nm, 200-msec, l-deg foveal test flash. Stiles's field displacement law was tested with increment thresholds upon monochromatic adapting fields of several wave-lengths. The data of all three observers reject the displacement law. Data that use a 10-msec-duration test flash likewise reject the displacement law. We conclude that the Pi-4 branch represents light adaptation controlled by more than one class of cone. A model of the Pi-4 detection pathway is proposed that quantitatively describes the increment-threshold data.

Adaptation, Physiological↗

PubMed1984

Acquired colour defects under restricted viewing time: a new diagnostic technique?

The effect of reduced viewing time on classification of colour vision by means of the City University Colour Vision Test is investigated in sufferers from diabetes and optic neuritis. The results suggest that patients with these conditions give non-normal responses when viewing time is reduced to 3.75 m. It may be possible to use the response obtained to diagnose the presence of ocular disease.

Adult↗

PubMed1975

Farnsworth 100-hue test in diagnosis of ethambutol-induced damage to optic nerve.

In patients treated with EMB, disturbances in colour vision may be the first and only symptoms of the onset of toxic damage to the optic nerves. Owing to its sensitivity, the Farnsworth 100-Hue test is of great value in the ophthalmic control examinations. Moreover, it permits observation of the dynamics of the toxic process. The three reported cases of damage to the optic nerves confirm the great importance of colour vision examinations, as regards the detection of the complications of EMB treatment.

Adult↗

PubMed1981

Chromatic adaption and the fundamental stimuli.

A bipartite adaption stimulus with a horizontal dividing line adapted the upper half of the retina to red or yellow light and the lower half to white light. Monochromatic test stimuli between 460 and 520 nm were presented to the red or yellow adapted portion of the retina. After desaturating the test stimulus with red light, it was possible to match it to a mixture of 458 and 520 nm. From these data one can plot on a mixture diagram the shifts in color produced by the two kinds of adaption. The data support a zone theory of color vision similar to that proposed by Adams.

Adaptation, Ocular↗

PubMed1984

What can colour thresholds tell us about the nature of the underlying detection mechanisms?

Two-colour increment thresholds, which have traditionally been analysed in terms of pi-mechanisms, were subjected here to a different form of analysis. Detection thresholds were measured for monochromatic test flashes and 10 bichromatic mixture combinations containing various proportions of two out of the five primaries: white, blue, green, yellow and red. The 1 degree, 0.5-s duration, foveal flashes appeared on a 1000-td blue background. All the thresholds were simultaneously fitted by assuming probability summation from a limited number of independent linear mechanisms. The assumption of two detection mechanisms provided a reasonable fit for all the bichromatic mixture thresholds. One mechanism received a positive contribution from both M and L cone types, whereas the other received an excitatory contribution from the L cone type, and an inhibitory contribution from the M cone type. The predictive power of the model was tested and compared to the pi-mechanism concept by fitting a spectral-sensitivity curve measured under identical conditions. It was concluded that parts of pi-mechanism curves probably reflect the responses of colour-opponent processes rather than those of single cone types.

Color Perception↗

PubMed1999

Effect of the tuberculostaticum ethambutol and stimulus intensity on chromatic discrimination in man.

In goldfish it has been shown that ethambutol shifts the threshold for wavelength discrimination without affecting the absolute sensitivity of the cones. In this study we demonstrate that a similar colour vision disturbance occurs in tuberculosis patients treated with ethambutol. After 2 months of ethambutol treatment, chromatic discrimination was measured with a computerized forced two choice (CD) test with isoluminant coloured stimuli and with three other colour vision tests: the Ishihara, the Oscar and the Lanthony Desaturated 15 Hue tests. The scores of the patient group (n = 19) on these four colour vision tests were compared with the scores of a group of control subjects (n = 33) and a group of congenital red/green colour-blind subjects (n = 5). A reduction of the stimulus intensity of 1 log unit caused a significant reduction in red/green chromatic discrimination, measured with the CD test in both, control subjects and patients. This intensity dependent reduction was significantly greater for patients than for controls. In this respect, man and goldfish behave similarly. Furthermore, the CD test showed the same ethambutol-induced reduction in chromatic discrimination at low intensity for the blue/green part of the spectrum. This has not been measured in goldfish. The origin of this ethambutol-induced colour vision disturbance must be at a post-photoreceptor site, because the Ishihara and Oscar tests, both designed to screen for photoreceptor-based, or primary red/green colour vision disturbances, did not discriminate between patients and control subjects. Thus, as in goldfish, we find that in patients ethambutol shifts the threshold for chromatic discrimination without changing the absolute sensitivity.

Adolescent↗

PubMed1977

Direct readout of spectral sensitivity for clinical and research purposes.

The application of spectral sensitivity measurements to clinical problems has been limited by the complexity of calculating the corrections for nonlinearity and non-neutrality of the neutral wedge and for the quantum intensity of the test beam. Asimple electronic system is described which performs all these calculations automatically, as the subject makes the sensitivity setting, and records the sensitivity on an XY plotter. A range of 5 log units is covered with an accuracy of 0.05 log units.

Color Perception Tests↗

PubMed1992

Visual function and the subsequent development of exudative age-related macular degeneration.

The eyes of 47 subjects with exudative age-related macular degeneration in the fellow eye were tested with a battery of visual function tests at baseline and followed for at least 18 mo. Fundus photographs also were obtained at baseline. These photographs were used to verify the absence of exudative lesions in the 47 eyes tested. Functional and funduscopic baseline data each were compared against outcome data obtained typically at 18 mo. The baseline data were analyzed for their ability to distinguish eyes that had developed detectable exudative age-related macular degeneration from eyes that had not. Eyes with relatively slow foveal dark adaptation rates despite low foveal quantum absorption capabilities (as inferred from the effects of test area on the Rayleigh color match) were especially likely to develop subretinal neovascularization. The resulting sensitivity/specificity and odds ratios were comparable to those of the most effective funduscopic risk indicators. Low S (blue) cone-mediated sensitivity also was associated with an exudative outcome.

Aged↗

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↗

PubMed2003

Colour discrimination learning in black-handed tamarin ( Saguinus midas niger).

Colour is one cue that monkeys use for perceptual segregation of targets and to identify food resources. For fruit-eating primates such as Saguinus, an accurate colour perception would be advantageous to help find ripe fruits at distance. The colour vision abilities of black-handed tamarins ( Saguinus midas niger) were assessed through a discrimination learning paradigm using Munsell colour chips as stimuli. Pairs of chips were chosen from an early experiment with protan and deutan humans. The monkeys (three males and one female) were tested with stimuli of the same hue, but different brightness values, in order to make sure that discriminations were based on colour rather than brightness cues. The results showed that the female, but not the males, presented an above-chance performance for stimuli resembling hue conditions under which tamarins forage (oranges vs greens). Colour vision in S. m. niger is discussed according to the advantages and disadvantages of dichromatism in daily search for food as well as to aspects regarding polymorphism in New World monkeys.

Animals↗

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↗

PubMed1979

Stargardt's disease and fundus flavimaculatus.

A study of 67 patients with a diagnosis of Stargardt's disease (juvenile macular degeneration) or fundus flavimaculatus showed that, apart from the ophthalmoscopic appearance, there is no clear distinction between these two disorders. The disease is an autosomal recessive macular degeneration that is bilateral and symmetrical in appearance, with diminished central vision as the hallmark symptom. The onset of symptoms usually occurred in the first or second decade, but a substantial number of patients were asymptomatic until the fourth or fifth decade. Psychophysical and electrophysiologic tests indicated that this is a localized and not a generalized retinal dystrophy. While the initial vision in the better eye was 6/12 (20/40) or better in one third of the patients, follow-up studies showed progression to levels between 6/30 (20/100) and 6/60 (20/400).

Adolescent↗

PubMed1990

[The diagnostic importance of the macular color test in vascular optic neuropathies].

A color-macular test is proposed for diagnosing functional changes in the optic nerve in acute vascular optic neuropathies. The diagnostic value of the test was proved in investigation of sick and clinically healthy fellow eyes of 80 patients with acute vascular optic neuropathies associated with atherosclerosis, aged from 30 to 74 years, as compared with a control group (60 persons of the same age and with the same general vascular pathology).

Acute Disease↗

PubMed1998

Incidence of idiopathic full-thickness macular holes in fellow eyes. A 5-year prospective natural history study.

PURPOSE: This study aimed to determine the incidence of idiopathic full-thickness macular hole (FTMH) in normal fellow eyes and to evaluate the role of electrodiagnostic and psychophysical tests in identifying eyes at risk. PATIENTS AND METHODS: A prospective longitudinal natural history study of a cohort of patients with unilateral holes and normal, asymptomatic fellow eyes without posterior vitreous detachment was conducted. Subjects underwent baseline examination, pattern reversal electroretinography, electro-oculography (EOG), and color contrast sensitivity (CCS) testing for protan, deutan, and tritan thresholds and were recalled for clinical examination at 18 months and 5 years. RESULTS: At baseline, 114 patients were examined. Eighty were available for review at 18 months, of whom 6 had full-thickness macular holes develop in the fellow eye. At 5 years, 67 of the remaining 74 patients who had not developed holes at 18 months were re-examined and a further 5 were found to have holes develop in the fellow eye. A posterior vitreous detachment without hole formation had developed in 20 fellow eyes at 5 years. Although mean pattern reversal electroretinography and EOG responses were within normal limits in affected and fellow eyes at baseline, mean CCS protan, deutan, and tritan thresholds were elevated significantly in affected eyes at baseline (P = 0.0001). Unaffected fellow eyes showed normal mean protan and deutan thresholds, but significantly elevated mean tritan thresholds (P = 0.01) at baseline. Mean tritan CCS loss was, however, similar in fellow eyes in which holes later developed and in fellow eyes in which holes did not. CONCLUSIONS: The Kaplan-Meier estimated risk of fellow eye involvement is 15.6% (range, 8.4%-22.3%; P = 0.05) at 5 years. Although electrodiagnostic and psychophysical testing was not predictive of fellow eye involvement, tritan CCS loss at baseline, in apparently normal fellow eyes, may indicate subclinical foveal dysfunction, the nature of which is unclear.

Adult↗

PubMed1978

Objective detection of reversible deficiencies in glaucoma by means of BECP.

The dynamic properties of the VECP trigger mechanism are used as a functional test for the glaucomatous eye. A light-emitting diode is used as stimulator. The test was performed under the condition of the functional isolation of the red colour mechanism (by means of selective colour adaptation technique). In any case, a delayed rise of stimulus luminance causes a delay of the VECP. This delay increases in patients with glaucoma. After a successful glaucoma operation the VECP delay diminishes again.

Color Perception Tests↗