PubMed · 532115
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E Hartmann, B Lachenmayr, H Brettel. 1979. The peripheral critical flicker frequency.. https://doi.org/10.1016/0042-6989(79)90227-x
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If a patternless field is modulated sinusoidally in time so that the luminance change in one eye is in counterphase to that in the other, the resulting flicker appears faster than if the modulation to both eyes has the same phase. If observers set the frequency and the amplitude of a comparison in-phase field so that it matches a neighbouring counterphase field, modulated at, say, 2.5 x its threshold, they set the frequency to twice the counterphase frequency, and the amplitude to a value that is, for a given frequency, a constant ratio of the modulation of the counterphase field. Counterphase stimulation thus appears to cause an internal second-harmonic signal. However, it is not possible to cancel this by adding a second harmonic component to the stimulus.
The temporal transfer properties of the visual system were examined in 157 patients with suspected acute optic neuritis or papillitis. Foveal modulation sensitivity was measured as a function of temporal frequency (DeLange curve) both for the affected eye and the unaffected fellow eye. Patients with acute optic neuritis typically show a reduction of foveal modulation sensitivity at all temporal frequencies, high temporal frequencies above 10 cps being more markedly affected. The aim of the present study was to determine the sensitivity and specificity of this simple psychophysical procedure for the diagnosis of neuritis or papillitis in a reasonably large population of patients with suspected acute optic neuritis or papillitis. In each case the final diagnosis was confirmed by evaluation of the clinical signs and symptoms, the course of disease and additional diagnostic procedures, e.g. electrophysiology, perimetry, neurological examination including CT, lumbal puncture and examination of cerebrospinal fluid. In 136 cases (86.6%) the result read from the DeLange curve was correctly positive or negative. In 17 cases (10.8%) the DeLange curve indicated a false-positive and in 4 cases (2.6%), a false-negative result.
Patients with multiple sclerosis (MS) have been shown to have a measurable deterioration in the ability to perceive temporal variations of light. Compared to the traditional critical flicker fusion (CFF) measure, a modified flicker fusion test showed an improved sensitivity for denoting neurological deficit in temporal vision. One hundred twenty-two patients with MS were examined. The traditional CFF test exhibited abnormalities in 48%; the modified test exhibited abnormalities in 78% of the same patients. These results appear to be independent of whether or not the demyelinating disease clinically involved the visual system. Also, the percentage of abnormalities demonstrated by combining both techniques was unexpectedly high (60% to 80%) in patients with minimal evidence of neurological involvement.