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PubMed1989

[Fechner's paradox, a binocular vision test].

Fechner's paradox is a visual phenomenon which may be summarized as follows: a subject looks at an illuminated screen in binocular vision; one of the eyes is provided with a photometric neutral filter (density 1,3), the other eye remaining uncovered. When the uncovered eye is covered by means of a cover-test, the apparent luminosity of the viewing screen seems to decrease; but when the eye with the filter is covered by the cover-test, the apparent luminosity of the screen seems to increase: this fact is apparently paradoxical, since a part of the luminous stimulus of the eyes was suppressed: this is Fechner's paradox. The exact mechanism of this phenomenon is not yet clear; nevertheless, it is a primordial phenomenon of binocular vision, is easy to use in clinical strabological practice. Our present study was an application of Fechner's paradox in 119 strabismic subjects, 5 kinds of responses were obtained: 2 normal kinds of responses: Fechner's paradox symmetrical (41 subjects) or asymmetrical (29 subjects), i.e. 60% normal responses; and 3 kinds of pathological responses: mononuclear abolition (34 subjects), binocular abolition (10 subjects) and inversion of Fechner's paradox (5 subjects). The comparison between these responses and the clinical features was as follows: 1) Fechner's paradox was normal in 78% of subjects when the difference between the visual acuities of the two eyes was below 5/10, i.e. without true ambylopia; Fechner's paradox was abnormal in 74% of subjects when the difference was greater than 5/10; unilateral abolition of Fechner's paradox was not clearly related to the differences in visual acuity, but bilateral abolition and inversion of the phenomenon was related to ambylopia of one eye.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1976

[Objective vision test in very young children (author's transl)].

By means of the Catford Visual Acuity Apparatus it is possible to determine objectively the visual acuity even in very young children easily and in a very short time; in children aged less than one year in most cases only a binocular later on a monocular acuity could be ascertained. There are almost no difficulties caused by the language. The visual results of 100 patients are given, 63 of which were under 3 years old; 10 children were aged between 5 and 24 months. A control group of 30 patients was also tested with Pflüger optotypes, and the results were compared; half of them were as good as, half of them -- mostly slightly -- better than the results gained by the Pflüger-test. We can therefore recommend the use of the Catford Apparatus in very young children and in such cases where the visual acuit can be determined only under very difficult conditions. The results are exact and can be assumed to be the same as with Pflüger's optotypes. Moreover, the Catford's apparatus may be also used for the testing of aggravants.

Child, Preschool↗
PubMed1971

Vision testing.

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Amblyopia↗
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↗