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Results for “Color Vision Defects”

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At least 217 records · Page 12Linked to original sources
PubMed1978

Blue cone function in a family with an inherited tritan defect, tested with electroretinography and psychophysics.

The sensitivity of the blue cone system to low frequency flicker was tested with a psychophysical and an electroretinographical method. With the psychophysical method the subjects, members of a family with an inherited tritan defect, showed no sign of the presence of the blue cone system. With the electroretinogram the sensitivity was also significantly lower than in normal subjects, thus indicating a retinal origin of the tritan defect.

Adolescent↗
PubMed1976

New data on the vision of South American Indians.

A total of 466 males and 437 females from four Brazilian Indian tribes were tested for color blindness with Ishihara's plates. Defective persons were found in three of the four tribes, but when these and other groups are considered the evidence suggests that the frequency of this trait is lower among Amerindians than among Caucasian populations. Visual acuity tests were performed on 296 Yanomama Indians. Their visual acuity was apparently not as sharp as that of the Cayapo or Xavante. But the scarcity among the Yanomama of persons with serious visual impairment of subcutaneous nodules suggests that the focus of onchocerciasis discovered among them is of recent origin.

Adolescent↗
PubMed1976

Unilateral colour vision defect resembling tritanopia.

A case of unilateral tritan defect is described. Colour-naming experiments showed that the tritanopic eye could perceive multiple colour hues. Although the defect resembled congenital tritanopia, it was considered to be acquired secondary to retinal pathology.

Adult↗
PubMed1985

The genetics of tritan disturbances.

Tritan (blue-green) colour vision disturbances have been found in 79 individuals in six families, revealing an autosomal dominant mode of inheritance with a wide variability of test results within families. Evidence is presented that it is--in contradistinction to the X-chromosomally inherited red-green defects--incorrect to make a subdivision between dichromasia (tritanopia) and anomalous trichromasia (tritanomaly). On the basis of three small screening series, totalling 1900 individuals, the frequency of tritan disturbances is estimated to be around 2 per 1000. Seven males have been observed carrying both inherited tritan and red-green defects.

Adolescent↗
PubMed1989

Effects of viewing conditions on standard measures of acquired and congenital color defects.

We examined the effect of variations in viewing distance and viewing duration on the performance of color-normal observers with four standard tests of color vision. Significant effects of the experimental manipulations were obtained: both increasing viewing distance and decreasing viewing duration significantly increased the number of errors made by observers. Moreover, the four tests differed widely in their sensitivity to the variations in viewing conditions. Practical implications of the findings for the administration and selection of plate tests are discussed, and possible mechanisms underlying the results are suggested.

Color Perception↗
PubMed1990

Cone dystrophy and supernormal dark-adapted b-waves in the electroretinogram.

A male patient suffering from cone dystrophy was followed over 9 years. In addition to the typical clinical and electrophysiologic signs, supernormal b-waves were found in the dark-adapted electroretinogram. Our case is compared with 12 similar patients described in the literature. Our patient differed from the other patients in the following aspects: he was male and had a congenital stationary disease with a small pigment epithelial scar in the left eye only and no other fundus changes up to the age of 22 years. He did not complain of night blindness. The dark-adapted electroretinogram of our patient showed a normal b-wave threshold with increased b-wave amplitudes and markedly prolonged b-wave latencies and implicit times. This combination of signs has not been reported to date in any other patient and points towards a postreceptoral defect of the interneuronal connection.

Adolescent↗
PubMed1976

Examination of colour vision by use of induced contrast colours. Design of a new series of tissue paper contrast tests.

The ability to induce contrast colours is evident in normal persons by the tissue paper contrast principle. However, tests of good quality are not easily available. The design of a new series of charts follows two principles: 1) Selection of background hues in accordance with the maximally desaturated regions of the spectrum as seen by the colour defectives. 2) Exact adjustment of the neutral test field (constituted by the chart figures) in order to eliminate any false clue due to brightness contrasts. By introducing chart figures of alternative grey values appropriate tests can be attained for each type of colour vision defect. 37 persons with congenital colour defect and 15 persons with acquired defects were examined. The charts, according to the criteria for selection, proved to be selective in their screening efficiency.

Adolescent↗
PubMedDate not supplied

Color vision testing.

1. Color deficiency occurs in about 8% of the population, due to alterations in the chemistry of one of the three receptive pigments for colored light, or the substitution of one pigment for another in the photoreceptor cones. 2. Subjects with pigment alteration can see a broad range of color; those with substitution of one pigment for another have broad areas of color perception defect. 3. The most common tests are pseudoisochromatic (color confusion) plates, designed with patterns hidden to the color deficient. Other tests use colored caps, tracing patterns, or an anomaloscope.

Color Vision Defects↗