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At least 1,441 records · Page 80Linked to original sources
PubMed1999

Research note: a multidimensional scaling comparison of color metrics for response times and rated dissimilarities.

Individual-differences multidimensional scaling was applied to a set of proximity data for equiluminant lights (Paramei & Cavonius, 1999) to explore any differences between two data collection procedures (rated dissimilarities, and same/different response times [RTs]), as well as between color-normal and abnormal observers. Two conclusions emerged: (1) The pattern of similarities from observers with anomalous color vision can be understood in terms of a compressed color plane (the weighted Euclidean model of individual differences); and (2) there is evidence that the color "plane" is either curved or governed by a non-Euclidean distance function. When color-normal observers are examined in the weighted-Euclidean framework, minor differences emerge between RT and rating data. But the main distinguishing feature of RT data is a pattern of decreasing accuracy for larger color distances. This must be taken into account, since it can itself induce curvature.

Color Perception↗
PubMed1982

Post-receptor chromatic mechanisms revealed by flickering vs fused adaptation.

For both normals and dichromats, adaptation to certain pairs of alternating monochromatic caused reduced sensitivity for detection of some test wavelengths when compared to sensitivity losses caused by adaptation to the fused (supra-CFF) sums of the same lights. Since the two adaptation conditions caused equivalent photopigment depletion, and since sensitivities to some wavelengths did not differ between conditions, the effects are ascribed to post-receptor adaptation. Such post-receptor effects were not obtained when adapting wavelengths did not straddle the presumed "crosspoints" of opponent-colors mechanisms, and, when only one opponent mechanism was adapted, effects were absent for test wavelengths at the crosspoint of that mechanism. For the red vs green system, increasing the intensities of adapting wavelengths from 2.2 to 5.5 log td did not appreciably increase the magnitudes of postreceptor effects. Quantitative accounts for the results are derived from a vector model for color vision. The results provide general support for opponent-colors interpretations of normal and dichromatic vision and suggest that the flicker/fused adaptation paradigm is a useful tool for probing postreceptor mechanisms of vision.

Adaptation, Ocular↗
PubMed1998

Acute vision loss resulting from complications of ethanol abuse.

BACKGROUND: Alcoholism affects about 10% of men and 3% to 5% of women in their lifetime. It is a primary chronic disease with genetic, psychosocial, and environmental factors that influence its development and manifestations. METHODS: A 47-year-old alcoholic male manifested mild nutritional optic atrophy, chronic anemia, pancreatitis, and previous gastrojejunostomy and pancreaticojejunostomy. After an acute episode of hypovolemic blood loss from peptic ulceration, there was increased bi-temporal optic nerve head pallor with permanent vision loss, central scotoma, and an acquired red-green color vision defect. RESULTS: The genetic, psychosocial, and systemic effects of ethanol abuse--including anemia, cardiomyopathy, gastric/duodenal ulceration, pancreatitis, and neurologic deficits--are reviewed. Appropriate treatment and management of ocular manifestations and complications from alcoholism are discussed. Prophylactic topical therapy may be indicated to restore the balance between intraocular tension and optic nerve head perfusion in an attempt to prevent further axonal loss. CONCLUSION: Alcohol-induced nutritional optic neuropathy should not be viewed as an isolated ocular entity, but rather as a potentially treatable neurologic problem. An interdisciplinary approach is essential optimal in the management of the alcoholic patient.

Acute Disease↗
PubMed2002

Color naming and the phototoxic effects of sunlight on the eye.

Many languages have no basic color term for "blue." Instead, they call short-wavelength stimuli "green" or "dark". We show that this cultural, linguistic phenomenon could result from accelerated aging of the eye because of high, chronic exposure to ultraviolet-B (UV-B) in sunlight (e.g., phototoxic lens brunescence). Reviewing 203 world languages, we found a significant relationship between UV dosage and color naming: In low-UV localities, languages generally have the word "blue"; in high-UV areas, languages without "blue" prevail. Furthermore, speakers of these non-"blue" languages often show blue-yellow color vision deficiency. We tested our phototoxicity hypothesis in a color-naming experiment, using computerized, colorimetric simulations of Munsell colors as viewed through clear and brunescent lenses. As predicted, our young subjects used "blue" as in English when the simulated lens was clear, but named colors as in tropical languages when the lens was dense. Our within-subjects design precludes a cultural explanation for this result.

Adolescent↗
PubMed1978

Opponent hues in visual masking.

Temporal interactions among opponent and non-opponent hues were investigated in a visual masking paradigm in which both backward and forward temporal sequences were employed. Subjective confidence ratings rather than identification thresholds alone served as response indicators for masking sequences. Results indicate that in the backward sequence (test stimulus followed by masking stimulus) a greater masking effect occurred when the stimuli were of non-opponent hue pairs (red-yellow, red-blue, green-yellow, green-blue) than when compared with opponent hue pairs (red-green, yellow-blue). For the forward sequence (test stimulus preceded by masking stimulus) the masking effect was reduced when compared with the backward sequence. These findings appear to reflect the presumed temporal and spatial antagonistic qualities of opponent hue processes as postulated in the Hering model of color vision.

Color↗