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At least 469 records · Page 26Linked to original sources
PubMed1975

Predictive validities of several clinical color vision tests for aviation signal light gun performance.

Scores on the American Optical Company (AOC) test (1965 edition), Dvorine test, Farnsworth Lantern test, Color Threshold Tester, Farnsworth-Munsell 100-Hue test, Farnsworth Panel D-15 test, and Schmidt-Haensch Anomaloscope were obtained from 137 men with color-defective vision and 128 men with normal color vision. The validity of each of these tests in predicting scores on the aviation signal light gun was assessed by using daytime and nighttime administrations of the light gun as the criteria. Two "best sets" of plates from the AOC and Dvorine tests were selected by calculating a multiple regression equation in a stepwise manner with the nighttime and then the daytime administration of the signal light gun test as the criteria. Based on a graphic presentation of the miss and false alarm rates for each test at various possible cut scores, suggestions were made regarding the use of each test and the selection of optimal pass/fail scores.

Aerospace Medicine↗
PubMed1993

Genetic basis of polymorphism in the color vision of platyrrhine monkeys.

It was earlier proposed that the polymorphism of color vision observed in some neotropical monkeys could be accounted for by assuming that these animals have only a single photopigment gene locus on the X-chromosome. Three kinds of evidence have been added to existing data sets in an effort to evaluate the adequacy of the single locus model: (1) photopigment complements of squirrel monkeys (Saimiri sciureus) have been determined using electroretinogram flicker photometry; (2) photopigment pedigrees have been established for several families of squirrel monkey; (3) X-chromosome pigment genes obtained from six dichromatic monkeys (three squirrel monkeys; three tamarins--Saguinus fuscicollis) have been examined to search for sequence polymorphisms at those gene loci believed crucial for spectral tuning. All of these results are in accord with the idea that some species of platyrrhine primate have only a single type of photopigment gene on the X-chromosome.

Animals↗
PubMed2001

The molecular genetics and evolution of red and green color vision in vertebrates.

To better understand the evolution of red-green color vision in vertebrates, we inferred the amino acid sequences of the ancestral pigments of 11 selected visual pigments: the LWS pigments of cave fish (Astyanax fasciatus), frog (Xenopus laevis), chicken (Gallus gallus), chameleon (Anolis carolinensis), goat (Capra hircus), and human (Homo sapiens);and the MWS pigments of cave fish, gecko (Gekko gekko), mouse (Mus musculus), squirrel (Sciurus carolinensis), and human. We constructed these ancestral pigments by introducing the necessary mutations into contemporary pigments and evaluated their absorption spectra using an in vitro assay. The results show that the common ancestor of vertebrates and most other ancestors had LWS pigments. Multiple regression analyses of ancestral and contemporary MWS and LWS pigments show that single mutations S180A, H197Y, Y277F, T285A, A308S, and double mutations S180A/H197Y shift the lambda(max) of the pigments by -7, -28, -8, -15, -27, and 11 nm, respectively. It is most likely that this "five-sites" rule is the molecular basis of spectral tuning in the MWS and LWS pigments during vertebrate evolution.

Amino Acid Sequence↗
PubMed1998

Validity of the Holmes-Wright lantern as a color vision test for the rail industry.

A simulated field test was designed to determine whether the Holmes-Wright A lantern (HWA) is a valid color vision test for the rail industry. The simulation replicated viewing rail signal lights at 0.8 km distance under daylight conditions. Using the worst-normal as the maximum number of allowable errors on the simulation, 94% of the color-defectives failed both tests on the first trial and 92% failed at the second session. The HWA had a higher false negative rate than a false alarm rate. The majority of individuals who had discrepancies on the two tests were mild deutans. Results from the Ishihara test were marginally better at predicting performance on the simulation.

Color Perception Tests↗
PubMed1996

Color vision in the manatee (Trichechus manatus).

Four manatees were trained to discriminate between a colored stimulus and a shade of gray in a two-fold simultaneous choice situation. The colors blue, green, red and blue-green were tested against shades of gray varying from low to high relative brightness. The animals distinguished both blue and green from a series of grays but failed to discriminate red and blue-green from certain steps of grays. The manatees could not discriminate between a UV-reflecting white target and an UV-absorbing white target. The results indicate that manatees possess color vision which is most likely dichromatic.

Animals↗
PubMed1973

Color-vision mechanisms in the peripheral retinas of normal and dichromatic observers.

It is possible that so-called normal trichromatic vision occurs only between the central blue-blind fixation area and about 30 degrees peripherally. Beyond about 30 degrees vision has been alleged to become dichromatic (red-green blind), and beyond about 60 degrees , monochromatic. Hence every form of color blindness may characterize various zones of the normal retina. We have studied mechanisms of peripheral color vision, mainly by measuring the spectral sensitivities of the blue-, green-, and red-sensitive systems, isolated by differential color adaptation. In normal observers the sensitivity of the blue-mechanism falls off about 2 log units by 80 degrees out. The green- and red-sensitive systems decline only about 0.7 log unit over the same range. Protanopes, deuteranopes, and tritanopes exhibit comparable changes. We have not found any color mechanism present centrally to be wholly lost peripherally. Nor, for dichromats, have we found any mechanism missing centrally to be present peripherally. Whatever evidences of peripheral color blindness have been observed appear to involve other mechanisms than failure of receptors, probably including some fusion of neural pathways from receptors to centers.

Color Perception↗
PubMed1992

Absence of smooth motion perception in color vision.

We have tested the behavioral evidence for a separation of the processing of color contrast from motion in the human visual system. Two different aspects of motion perception are examined; the identification of the direction of movement of a chromatic grating and the perception of smooth motion. The results show that color vision is at no great disadvantage in the identification of direction of movement, since this can be done at color contrasts quite close to detection threshold over a wide range of spatial and temporal frequencies. However, we find that subjects can identify direction without having the genuine perception of smooth motion. Smooth motion perception is revealed to be highly impaired since it is detected only at very high color contrasts and over a narrow range of spatial temporal conditions.

Color Perception↗
PubMedDate not supplied

Multidimensional scaling of D15 caps: color-vision defects among tobacco smokers?

Tobacco smoke contains a range of toxins including carbon monoxide and cyanide. With specialized cells and high metabolic demands, the optic nerve and retina are vulnerable to toxic exposure. We examined the possible effects of smoking on color vision: specifically, whether smokers perceive a different pattern of suprathreshold color dissimilarities from nonsmokers. It is already known that smokers differ in threshold color discrimination, with elevated scores on the Roth 28-Hue Desaturated panel test. Groups of smokers and nonsmokers, matched for sex and age, followed a triadic procedure to compare dissimilarities among 32 pigmented stimuli (the caps of the saturated and desaturated versions of the D15 panel test). Multidimensional scaling was applied to quantify individual variations in the salience of the axes of color space. Despite the briefness, simplicity, and "low-tech" nature of the procedure, subtle but statistically significant differences did emerge: on average the smoking group were significantly less sensitive to red-green differences. This is consistent with some form of injury to the optic nerve.

Color Perception↗
PubMed1982

Age and temporal resolution in color vision: When do red and green make yellow?

The ability to temporally resolve color stimuli was compared in young and old adults. Stimuli consisted of pairs of brief green and red flashes separated by six levels of interstimulus interval and presented at two different luminance levels. Integration of the color pairs to produce reports of yellow decreased significantly with increasing interstimulus interval, particularly for the younger group. This difference remained when the age-related loss in retinal illumination was compensated by increased stimulus luminance. These data indicate a decline with age in temporal resolution in color vision. Further, they suggest that age differences in temporal resolution can be more appropriately attributed to age-related differences in visual/neural mechanisms than to changes in the ocular media or photoreceptor activity.

Adult↗
PubMed1992

Color vision and contrast sensitivity tests in early diagnosis of primary open-angle glaucoma.

Color vision was examined by the Farnsworth 100 hue test in 48 eyes with ocular hypertension (OHT). Thirteen eyes had a general loss of color discrimination and 8 had a blue-yellow axis. Spatial contrast sensitivity was tested in 31 eyes with OHT by the Mentor B-VAT and was reduced in 8 of them. Temporal contrast sensitivity was explored in 40 eyes with OHT by the Flickersyst&m and showed abnormal responses in 11 eyes. According to the lack of specificity of the responses and the overlapping of the results of normal eyes and OHT eyes, those tests are not useful for classifying an individual patient. Such investigations however have the interest to show that macular mediated functions may be impaired early in glaucoma.

Adult↗