Color-blind Subjects Research Articles

Light-induced increase in amplitude of electro-oculogram. Evoked with blue and red lights in totally color-blind and normal humans.

Blue and red lights chosen to evoke equally large increases in the amplitude of the electro-oculogram (EOG) in the normal human eye were used to test eyes with defective cone function. It was found in five totally color-blind subjects that the response to red light was below the normal range, whereas the response to blue light was within the normal range. The results indicate contribution of both rod and cone mechanisms to the generation of the light-induced response of the normal human EOG.

Photopic luminosity measured by the method of critical frequency

Three color-normal and two color-blind subjects gave photopic luminosity functions by the method of critical frequency. By this method, the subject adjusts the radiance of intermittent light to produce threshold flicker for a constant rate of intermittence at various wavelengths. A family of contours was measured for various intermittence rates and a luminous efficiency function was derived from each contour. The average efficiency function for colornormals compared well with that of Judd's revision for the CIE Standard Observer. However, contours showed systematic changes as frequency of intermittence increased; these changes reflect the fact that the slopes of the CFF-log radiance functions vary with wavelength.

Color blindness among Aymara in Chile.

AbstractNine color blind subjects were discovered in a survey of 140 Aymaras of Arica, Chile, using as screening test a portable Anomaloscope, Ishihara tables and Hardy‐Rand‐Ritter plates. Pseudosisochromatic test failed on detecting four anomalous trichromates. Seven color blind subjects revealed foreign ancestors. Also a different prevalence of defectives among subsamples was observed. Thus color blindness variability within the sample could be explained by gene flow. It is proposed to use anomaloscopes as a screening device in order to survey with accuracy color vision genes in human populations.

Occupational possibilities of colour defectives.

The purpose of most of the color vision examinations made it in my clinic is to decide whether or not an applicant fulfills the visual requirements of the traffic sector. Many I clinics have only pseudo-ice and plates, and often only plates approved for the license issue in this particular place. This routine can easily have is a shortcoming that the ophthalmologist gets a biased idea of the problems and possibilities of colorblind subjects, and it may for example make it difficult for him to give advice if the principle has doubts about the employment of a colorblind apprentice. Furthermore she do I said karma plates are used as the only standard at cycle technical tests of the premises. Such processes are strongly rejected by Cowan making (1942) who states clearly and briefly that the value of a pseudo-ice of the plate as regards to prognosis of occupation is comparable to a visual acuity chart containing nothing but 6/6 letters utilize chromatic plates can be used only to decide whether the color since is normal or not, and besides, this decision is not clear Language: en

Factors affecting luminance additivity at threshold among normal and color-blind subjects and elaborations of a trichromatic-opponent colors theory

In experiments which supplement earlier findings it was found that (a) gross failures of Abney's law occurred in field sizes ranging from 20′ to 2°, (b) two-alternative temporal forced-choice procedures yielded nonadditive effects similar to those obtained with adjustment methods, (c) protanopes and deuteranopes differed from normals in that they showed complete additivity with mixtures of reds and greens, but were similar to normals in the extent to which they demonstrated blue plus green additivity failures. The data from color-blind Ss suggested that each type of dichromat possesses only one of the three possible classes of opponent-color cells which can be constructed using two of three possible receptor systems.

Spatial and chromatic interactions in the lateral geniculate body of the rhesus monkey.

Spatial and chromatic interactions in the lateral geniculate body of the rhesus monkey.

The performance of color-blind subjects on the color aptitude test.

The performance of color-blind subjects on the color aptitude test.

Studies of the a-wave in the human electroretinogram.

The electroretinogram (ERG) in response to high-intensity stimuli represents a sequence of waves beginning with a negative deflection—the a-wave. Previous studies have analyzed this complex wave in terms of photopic and scotopic components. These analyses were derived from the behavior of the a-wave during dark adaptation and with stimuli of different wavelengths. 1-4 This assumption of a duplex nature of the a-wave has been strengthened by the fact that it frequently appears to be split into two parts separated by a step, or hump. Based on this finding, tentative schemes have been suggested in which the photopic and scotopic components of the a-wave are distinguished by different latencies. 1,4 The present study deals with the a-wave of normal, congenitally night-blind, and totally color-blind subjects in response to white-light stimuli of different intensities. Since the rapid course of the a-wave prevents adequate measurements when it is registered with standard ERG techniques,

Comparative electroretinographic studies in congenital night blindness and total color blindness.

In the analysis of the human electroretinogram, the study of subjects with congenital night blindness and total color blindness is of great value. The absence of specific electroretinographic components in these anomalies simplifies the complex pattern of response, allows a more detailed investigation of the remaining components, and aids in the analysis of the photopicscotopic nature of the different waves. However, the few investigations which deal with the electroretinogram in congenital night blindness and total color blindness have studied each condition separately; therefore, no direct comparison has been made between their electroretinographic responses. The purpose of this study is to investigate quantitatively the influence of dark-adaptation and stimulus intensity on the electroretinogram of normal, congenitally night-blind, and totally color-blind subjects,* examined under identical experimental conditions. <h3>Subjects</h3> The night-blind subject is a 28-year-old married white woman. She has been aware of poor night vision in both eyes since childhood, nonprogressive in

Subjective Spectral Band Limits* Under Controlled Conditions†‡

Subjective spectral band limits have been established under controlled conditions as to dark adaptation of the eye, luminance of the spectrum (0.8 millilambert at 555 mμ) at the eyepiece slit, small visual angle (2.2°) of the slit, and observed band width of 0.6 mμ at 400 mμ to 1.3 mμ at 700 mμ. One hundred and twenty-five students have been subjected to the test. Color-blind persons were excluded. The mean values of transition points established by these tests are as follows: Transition from infra-red to red, 744 mμ; red to orange, 614 mμ; orange to yellow, 597 mμ; yellow to green, 582 mμ; green to blue, 514 mμ; blue to violet, 476 mμ; and violet to ultraviolet, 419 mμ.Color transitions of some color-blind subjects, exceptional subjects and subjects pre-exposed to various conventional light sources, are also given.

Electrophysiological studies of color-blindness.

The time course of changes in electrical excitability of the eye after 2 seconds' illumination by white light was investigated in normal and color-blind subjects. 1. The excitability curve obtained by plotting ζ-values or percentage increases in electrical excitability as ordinates against the time after the end of illumination as abscissae showed a single maximum at 2 seconds in normal subjects. In the deuteranope, two distinct elevations were found on the excitability curve, while the curve taken from the protanope showed a single maximum At one second. 2. The excitability curve for white light obtained from deuterano-malous subjects showed distinct three elevations which were termed R, G and Bin the order of rapidity of development. It was shown that the three elevations represent three independent processes but not different phases of one and the same process. The development of the G process is weak in the deuteranomalous and entirely lacking in the deuteranope, so that there appear only two elevations in the excitability curve of the deuteranope. 3. The G elevation of the excitability curve taken from deuteranomal-ous subjects disappeared at a sufficiently low intensity of illumination, so that the excitability curve taken under such conditions could not be dis-tinguished from that of the deuteranope. 4. The wave-lexxgth dependence or spectral locus of each color pro-cess was investigated. The locus of the B process has its maximum at about 460mμ in all cases of normal and color-blinds. The R locus could not be found in the protanope, and the G locus was found lacking in the deut-eranope. The R and G loci obtained from the color-blinds had a maximum at 610 mμ and 530 mμ respectively. The locations of these maxima did not coincide precisely with those of the corresponding loci taken from the fovea of normal man, but showed a close agreement with those of the cor-responding loci taken from a parafoveal region of the retina of normal man. In the deuteranomalous, the B and R loci showed normal behavior in all respects, but the G locus was found always smaller than normal not only in the maximum height but also in the extent of the locus over the spectrum. In one case of the deuteranomalous, the G process extended over such a narrow range of the spectrum as between 490mμ and 570mμ. It is worthy of note that the defect in color vision was so severe in this case that it could not be distinguished from a true deuteranope by tho routine anomaloscopic test and by our method of excitability curves for white light.

Brightness, visual acuity and colour blindness

1. Measurements have been made of the dark-adapted foveal threshold of normal and colour blind persons in five parts of the spectrum using a 1° circular test field. 2. Compared to normals, protanopes (red-blinds) show an elevation of the threshold which increases slowly from blue to yellow and rises rapidly thereafter until in the red the threshold is more than ten times as high as normal. Deuteranopes (greenblinds) do not show so high an elevation, their maximum in the green being only about 70% above normal. 3. These threshold elevations correspond to luminosity losses in the spectrum. For the protanope the total loss in the spectrum is nearly one-half of the normal luminosity; for the deuteranope it is nearly two-fifths of normal. 4. Measurements were made of the illumination necessary for equal visual performance in normal and colour blind subjects. It was found that protanopes require 119% and deuteranopes 55% more light to achieve a visual acuity of 0.29 reciprocal minutes. These values agree closely with those found in the luminosity measurements. 5. Such losses support the idea that colour blindness corresponds to the loss of one of the three receptor systems usually postulated to account for normal colour vision. However, the colour sensations reported by colour blind persons, especially monocular colour blinds, do not support the idea of a lost or inactivated receptor system. A fresh explanation for colour blindness is needed to reconcile these conflicting kinds of evidence.

Colour-Blindness: with a Comparison of Different Methods of Testing Colour-Blindness

THAT theories are useful servants but bad masters is borne out by a study of this book. It embodies “the results of research on red-green colourblind subjects,” and “the tests were carried out unbiased by any preconceived theory and no rigid classification was attempted during the experiments themselves.” A mass of observations on ten excellent subjects, eight being students attending the graduating course in experimental psychology, and two science students, has been accumulated. All will admit that such material is of great value, but that alone it is unlikely to afford an explanation of the complex problem under investigation. Its ultimate value will depend upon the deductions drawn from it, and these must necessarily involve theoretical considerations which may support or be adverse to previous theories. In this respect it is essential that the investigator should be fully cognisant of the facts which have been elicited by previous observers, whether they support any such theory or not.

Persistence of Vision in Color-blind Subjects

Persistence of Vision in Color-blind Subjects