[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.