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PubMed1958

Color defect and color theory; studies of normal and colorblind persons, including a subject color-blind in one eye but not in the other.

It is important to find answers to two questions concerning the visual discriminations of dichromatic persons, especially deuteranopes: (i) Do such persons show a loss of sensitivity to various wavelengths of the spectrum as compared with normal subjects? (ii) What colors do they see? A number of experiments were performed on the first question. First, luminosity curves were determined on three groups of subjects, consisting respectively of five protanopes, six deuteranopes, and seven normal individuals. As compared with normal subjects, protanopes show a loss of luminosity in the red, whereas deuteranopes show a loss in the blue-to-green region of the spectrum (See 10). Second, we examined the luminosity curves of a subject whose right eye is classifiable (on the basis of color-mixture determinations) as normal and whose left eye is classifiable as dichromatic. (The hue discrimination curve for her dichromatic eye seemed comparable to the curve of the usual deuteranope except in the violet, where it manifested relatively good discrimination.) The luminosity function for this subject's dichromatic eye, determined by data on threshold and flicker, exhibits the same type of luminosity loss in the blue and green regions of the spectrum as was shown by our group of six deuteranopes. Only unilaterally dichromatic subjects can tell us how colors seen by a dichromatic eye appear to a normal eye. In the color-blind eye, our unilaterally dichromatic subject sees wavelengths below and above her neutral ("grey") point (which occurs at 502 mmicro) as, respectively, a blue equivalent to about 470 mmicro and a yellow equivalent to about 570 mmicro in her normal eye. The results on (i) luminosity loss and (ii) the seeing of wavelengths above 502 mmicro as yellow are considered theoretically. The seeing of yellow by deuteranopes and protanopes may be accounted for by an idea based on Leber-Fick transmation theory. It is proposed that the characteristic sensitivities of the red and green receptors become similar while no change takes place in their central brain connections. Losses may be introduced into the transformed sensitivity curves to indicate appropriate degrees of luminosity deficit for deuteranopes and protanopes.

Color↗
PubMedDate not supplied

The effect of test distance on the CN lantern results.

The purpose of this study is to determine how the viewing distance affects the pass/fail results of the CN Lantern (CNLan). The CNLan is a color vision test designed for the railway industry. It presents 15 triplets of colored lights that could be any combination of red, green and yellow. The test was viewed from 4.6 m and 2.3 m. Sixty-seven color-defectives participated in the first part of the study. Sixty-six percent of the subjects repeated the experiment 10 days later. There was a significant (P < 0.05) decrease in the mean number of errors from 7.6 to 4.3 as the distance decreased. There was also a corresponding increase in the percentage of subjects who passed from 9.0% at 4.6 m to 20.9% at the 2.3 m viewing distance. None of the subjects who passed at the longer distance failed at the shorter distance. The replication results were statistically identical to the first session (P > 0.05). Decreasing the CNLan viewing distance by 50% does decrease the number of errors and increase the pass rate. This indicates that some color-defectives could work in the railway yards where the sighting distances for the signal lights are shorter than on the main track.

Color Perception↗
PubMed1985

Color blindness and Rorschach color responsivity.

Color vision deficits occur in 10% of the American white male population. Thus, color blindness may invalidate diagnostic hypotheses generated from Rorschach data. The Rorschach protocols of 43 white, college male color-blind subjects were compared to the protocols of normally sighted controls. The color-blind group manifested fewer pure "C" responses. No significant between group differences emerged for any of the other primary Rorschach color variables. Pure "C" responses rarely figure prominently in Rorschach evaluations, and the apparent lowered frequency of these responses by the color-blind is insufficient to warrant modification of current Rorschach practice. The data suggest that color blindness is unlikely to confound Rorschach assessment.

Adult↗
PubMed2000

Daylight, biochrome surfaces, and human chromatic response in the Fourier domain.

We first report Fourier analyses of a collection of 348 daylight spectral power distributions and 1,695 biochrome surface reflectance functions. The power spectra of the daylights are low pass with more than 99% of spectral power below 1 cycle/300 nm and 99.9% below 3 cycles/300 nm. The power spectra of reflectance functions are also low pass with more than 99% of spectral power below 4 cycles/300 nm and 99.9% below 11 cycles/300 nm. Consequently, the resulting color signals are typically low pass with, for our samples, an estimated frequency cutoff of 5 cycles/300 nm. Theoretical and experimental data concerning human chromatic response in the frequency domain show that this limit corresponds to the highest frequency that the color system can resolve. The implications for normal and abnormal human color vision are discussed.

Color↗
PubMed1985

Association of hue discrimination loss and diabetic retinopathy.

The results of Farnsworth-Munsell 100-hue, visual acuity, and visual field testing were compared with the severity of retinopathy in a group of 90 diabetic patients. The patients showed significantly higher than expected Farnsworth-Munsell 100-hue scores, with a tritanlike axis, compared with published age norms for nondiabetic individuals. The magnitude of the acquired blue-yellow hue discrimination defect correlated significantly and to a similar extent with both the severity of overall diabetic retinopathy and the severity of macular edema and hard exudate formation. Visual acuity loss correlated somewhat more significantly with macular edema than with overall retinopathy, whereas the converse was true for visual fields. For all visual function tests, the correlations were more significant for fluorescein leakage in the macula than for capillary nonperfusion in the macula. Abnormal hue discrimination was found in 65% (32/49) of eyes with proliferative diabetic retinopathy, suggesting a potential role for this test in screening for proliferative diabetic retinopathy in primary care facilities. Also, because the ability of diabetic patients with color vision deficiency to perform color-dependent tests for urinary and blood glucose may be impaired, such patients should be made aware of this potential problem.

Adult↗