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Biomedical subjects

B Kedzia

Publications and source records attributed to B Kedzia.

At least 19 recordsLinked to original sources
PubMed1994

Resolving power to narrow and extended light sources and its influence on legibility of the optotypes.

The resolving power of the human visual system has been found to depend on the sizes of the light sources. The sources used in this experiment were two rectangular white fields separated by a vertical black bar. The minimal angle of resolution measured on five subjects decreased by about 10-20 times while the light sources were extended up to the effective range of spatial summation. For larger sources no significant changes of spatial resolution were observed. The experimental data revealed biphasic dependence of the minimal angle of resolution on the sizes of the light sources and permitted estimation of the effective range of spatial summation for 3-9 min arc. This range encompasses the angular diameters of typical optotypes recognized by normal observers (visual acuity greater than 1, optotypes smaller than 5 min arc), therefore we show how the spatial arrangement of the lines and strokes of optotypes determines their legibility.

Adult↗
PubMed1994

Resolving power of the human visual system to monochromatic stimuli.

The resolving power in monocular, foveal vision was found to depend on the size of a white light source made of two white rectangles separated by vertical black bar. The question arises whether the wavelength of light influences this dependence. An experiment was done on three subjects using six monochromatic lights the range 450-625 nm, and white light for control measurements. The diagram of the dependence of the minimal angle of resolution on the source size takes the shape of a biphasic curve, i.e. decreasing and constant function. The wavelength was found to have no impact on the curve shape or values. The data points obtained for white light coincide with those for monochromatic lights. The results confirm a thesis that all three colour mechanisms in the human visual system are stimulated and are active in spatial summation processes, but to a degree conditioned by a spectral sensitivity of the particular colour apparatus. It was confirmed that all colour mechanisms have potentially the same acuity but the axial chromatic aberration causes observed reduction of acuity.

Adult↗
PubMed1992

[Use of the Foucault's test for determining the contrast sensitivity of the visual system].

The authors present the thesis that in apperception of the Foucault's test in condition of a threshold contrast only the first harmonic component is decisive; in connection with this one can replace the sinusoidal tests applied for the demarcation of the sensitivity curve of the visual system to contrast by Foucault's test. They point to the eventual possibility--if the influence of the following components would prove to be essential--of using the Foucault's test together with the sinusoidal test in order to make the diagnosis of pathological conditions more selective. The CSF function was designated by means of the sinusoidal and Foucault's tests seen on a monitor screen using the methods of contrast increase. In 8 subjects observing simultaneously one discovered that for the frequencies larger or equal to 1.5 stop-1 one can apply the Foucault's test instead of the sinusoidal test. Below the space frequency of 1.5 stop-1 one observed differences between the values of sensitivity to contrast demarcated by means of both tests; these differences result probably from the influence of the higher harmonics of the Foucault's test on the apperception of the test.

Adult↗
PubMed1986

Stereopsis angle in relation to proximity and induced refractive errors.

Dependence of stereoacuity (SA) angle on the reciprocal of the test distance with positive, negative, and zero values of induced refractive errors is demonstrated with the three-rod test and the mean errors statistical method. Two male emmetropes and one hyperope showed linearly increasing dependence of SA angle on the reciprocal of the test distance within the subject's range of clear vision extended at both ends by 1 D. Linear regression coefficients were not influenced by the value of induced refractive error within +/- 2 D. Correlation coefficients in the case of corrected refractive error were about 0.90, but their mean value in the case of induced refractive errors was 0.83.

Adult↗
PubMed1986

Informeffia: a visual science concept.

The receptor path of an autonomous system is distinguished and the aims that could be achieved by preliminary modification of a carrier of information are discussed. Based on the discussion the receptor path is described as being informeffic if in the case of natural information carrier the structure of the receptor path is in the form that makes reception of information from surroundings and transmission to the processor most efficient. The kinds of informing, measurement of information, and visual system spaces of stimuli and of information are discussed. These resulted in formulation of the criterion of the visual system informeffia, and in the conclusions that correction procedures generally are designed to alter an existing aformeffic status of the visual system toward artificial informeffia and that the quantity of information can allow comparing efficiency of different correction procedures.

Humans↗
PubMed1985

Visual system emmetropia.

Based on the fundamental task of the visual system, which is to receive information from the surroundings and to transmit it to the central nervous system, the visual system is described as being emmetropic if the amount of information received through the visual pathways is maximum when the eyes are unaided. A mathematical model of the dependence of the amount of information received through the visual channels on the eye's refractive power and range of clear vision has been worked out. The model, by showing good correlation with common experience, confirms the hypothesis that the amount of information is a coefficient of an eye's approximation to emmetropia and that the criterion of emmetropia of an eye is a particular case of the criterion of emmetropia of the visual system.

Humans↗