Large-field S-cone flicker test.

Abstract

BACKGROUND: Disturbances of blue color vision and of temporal contrast sensitivity can indicate early damage in glaucoma. For the present study a quick and easy test was devised which examines both functions at one time by testing the temporal contrast sensitivity of a blue flickering light on an intense yellow background. METHODS: Large coextensive background and test fields (85 degrees) are used, making fixation uncritical. Detailed experiments were made in two normal subjects to derive spectral sensitivity curves from flicker-fusion frequency (FFF) versus intensity functions and to obtain complete temporal contrast-sensitivity (De Lange) curves under different levels of adaptation and test lights. After selection of appropriate luminances and one stimulation frequency from these experiments, test-retest variability was studied in four subjects in five repetitions. In addition, normal values were collected from 22 subjects. RESULTS: Spectral sensitivities for two levels of FFF (15 Hz and 44 Hz) agree with Stiles' pi 1 at the low and with pi 4 at the high FFF. Temporal contrast-sensitivity curves show a low-frequency section with peak sensitivity at 1 Hz and a high-frequency section with a peak at around 4 Hz. From the basic experiments the following conditions for the clinical examination were selected: Background luminance 2600 cd/m2, test luminance at 451 nm 0.8 cd/m2, stimulation frequency 4 Hz. The test-retest variability showed an acceptable intraclass correlation co-efficient (0.6). CONCLUSIONS: The present experiments carried out with a very large stimulus led to meaningful results which are in rather good agreement with results reported in the literature on small-field stimuli. The blue-on-yellow flicker test carried out under the conditions mentioned above is a quick and easy test which could be helpful in improving early glaucoma diagnosis.