[Determination of optokinetic reactivity by a sudden supra-optimal acceleration of the stimulus (author's transl)].

The authors describe a new method of optokinetic stimulation. The stimulus is applied during 3 successive sequences: the first and third include displacement of 1 to 2 black or white bands per second (apparent mean speed of 16 degrees/sec), while the second sequence comprises the sudden acceleration of 6 black or white bands per second (apparent mean speed of 59 degrees/sec.). Each sequence lasts 4 to 10 seconds. However many times the stimulus is repeated the optokinetic response becomes hyposynchronous at the frequency at which the bands are passing when the speed is increased, whereas the amplitude of the ocular responses is multiplied two to three times. The increase in the amplitude appears to be proportional to the reduction in frequency. In this way, optokinetic reactivity is tested when the subject looks in the three principal directions: horizontally, vertically, and obliquely. Particular types of reaction are observed in pathological conditions where they are either unadapted or incomplete, while absence of optokinetic reactivity can be found in all directions, several directions, or in one direction only.