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At least 1,621 records · Page 90Linked to original sources
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↗
PubMed1982

Phoria measurements using chromatic targets.

Von Graefe phoria measurements were obtained for ten prepresbyopic subjects at 40 cm and 6 m test distances using a vertical column of black letters on red, green, and white backgrounds. Phorias measured at 40 cm using red and white target backgrounds were similar, but the phoria measured using a green target background indicated a change toward greater exophoria. No difference in phoria measurements was found between all targets at 6 m.

Accommodation, Ocular↗
PubMed1983

Effect of X-Chrom lens wear on chromatic discrimination and stereopsis in color-deficient observers.

Four color-deficient observers and one normal trichromatic subject were evaluated with color vision and stereoacuity tests during 1 month of X-Chrom lens wear. For all color tests, performance of the normal subject was unaltered by X-Chrom lens wear. Color-deficient subjects demonstrated improved performance on the Ishihara pseudoisochromatic color plates, but either degraded performance or no change on the Farnsworth-Munsell 100-hue or Pickford-Nicolson red-green anomaloscope test. Three of the five subjects exhibited degraded stereoacuity in conjunction with X-Chrom lens wear. We conclude that the X-Chrom lens does not improve discrimination in color-deficient subjects and may alter stereopsis.

Color Perception Tests↗
PubMed1988

Laser-induced chromatic adaptation.

Detecting a target in a visually noisy back-ground depends on the ability of the observer to discriminate the target from the surrounding terrain. Visible laser irradiation at less than damage levels may act as a masking source by reducing the observer's ability to resolve differences in the visual scene. The experiment reported here specifically investigates the comparability of shuttered CW and Q-switched visible lasers to alter/degrade color discrimination. Visual evoked potentials (VEP's) were used to examine the short time course effects in monkeys of luminance-matched flashes from a 694 nm ruby Q-switched laser and 100 ms shuttered krypton CW laser (676, 568, and 531 nm lines). The test stimulus was a shifting pattern of alternating luminance-matched 510 and 550 nm green bars. With flashes equated to 4.8 log T-s, similar flash effect curves were seen, demonstrating 1.5-s changes in response magnitude. This level of flash did not extinguish the response to the stimulus. The flash effects curve was "W"-shaped, with an intermediate signal peak occurring at approximately 500 ms after the flash and whose level exceeded the baseline magnitude. The hypothesized mechanism for this result is an induced luminance imbalance caused by a transient shift in the peak color responsiveness of the visual system, which recovers with two different time constants. It is concluded that red and green colored laser flashes shift the color balance transiently in the visual system (yellow flashes to a lesser extent); thus, targets may change both hue and brightness after an observer receives colored flashes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Ocular↗
PubMed1991

Accommodative performance for chromatic targets in diabetes mellitus: a preliminary report.

Our objective was to evaluate the diagnostic potential of a new vision testing procedure for detecting subclinical visual dysfunction in patients with insulin-dependent diabetes mellitus (IDDM) and minimal or absent retinopathy. We used a method which challenged both the ocular focusing and color discrimination systems simultaneously. A computerized laser speckle optometer which measured changes in ocular refraction on a subjective criterion of speckle movement rather than perceived blur was used to measure the accuracy of steady-state accommodative responses. Five volunteers between 15 and 23 years of age who had IDDM and minimal background retinopathy participated in this study. Our results for this small group of diabetics showed that: (1) the overall binocular accommodative response profiles of diabetics for colored targets through increasing negative power ophthalmic lenses did not differ markedly from those of a control population; (2) diabetics exhibited a high sensitivity for perception of optical defocus; (3) the blood glucose level influenced the extent and accuracy of accommodative responses; and (4) the overall accommodative precision, when compared to a group of nondiabetics in the same age range, showed evidence of being more reliant on target colors. The theoretical and clinical implications of these findings are discussed.

Accommodation, Ocular↗
PubMed1997

Wavelength-dependent magnification and polychromatic image quality in eyes corrected for longitudinal chromatic aberration.

Theoretical calculations using a simple model eye in combination with achromatizing lenses or artificial pupils show that correcting wavelength-dependent refractive error or its effects can exaggerate wavelength-dependent magnification by up to a factor of 7. These calculations are confirmed experimentally, and their effects on retinal image quality are modeled. Because of the increased wavelength-dependent magnification, gains in polychromatic image quality produced by correcting wavelength-dependent refractive error (or minimizing its effects with small pupils) are generally restricted to a small region of the retina.

Color Perception↗
PubMed2004

Novel chromatic and structural biomarkers of diet in carotenoid-bearing plumage.

Previous attempts to establish a link between carotenoid-based plumage reflectance and diet have focused on spectral features within the human visible range (400-700 nm), particularly on the longer wavelengths (550-700 nm) that make these plumages appear yellow, orange or red. However, carotenoid reflectance spectra are intrinsically bimodal, with a less prominent but highly variable secondary reflectance peak at near-ultraviolet (UV; 320-400 nm) wavelengths visible to most birds but not to normal humans. Analysis of physical reflectance spectra of carotenoid-bearing plumages among trophically diverse tanagers (Thraupini, Emberizinae, Passeriformes) indicated that both the absolute and relative (to long visible wavelengths) amounts of short waveband (including UV) reflectance were lower in more frugivorous species. Striking modifications to the branched structure of feathers increased with frugivory. These associations were independent of phylogenetic relatedness, or other physical (specimen age, number of carotenoid-bearing patches) or ecological (body size, elevation) variables. By comparison, reflectance at longer visible wavelengths ('redness') was not consistently associated with diet. The reflectance patterns that distinguished frugivores should be more apparent to UV-sensitive birds than to UV-blind humans, but humans can perceive the higher plumage gloss produced by modified gross feather structure. Basic aspects of carotenoid chemistry suggest that increases in pigment concentration and feather dimensions reduce short waveband reflectance by the plumages of frugivores.

Animals↗