PubMed · 4717146
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R M Herrick. 1973. Foveal increment thresholds for multiple flashes.. https://doi.org/10.1364/josa.63.000870
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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.
In the Aulhorn flicker test, the subjective brightness of a steady field is matched to that of a flickering field at 50 to 0 Hz. The test gives pathologic values only for active optic neuritis (ON) and gives normal results for normal eyes and eyes with subsided ON and other diagnoses, with a specificity of 98% and a sensitivity of 85.5%. Characteristic variations of the curves of subjective brightness during the course of ON allow a subtle assessment of five different disease stages, and there is a clear distinction between various disease patterns, ie, acute, chronic, recurrent, diminishing, and subsided ON. This distinction is impossible on the basis of visual evoked potentials. The test can be done easily and quickly without major technical equipment, even in an ophthalmologist's office.