Reproducibility of Duration of Latency Time in Unidirectional Per-Rotatory Nystagmus

Abstract

Sixty-eight healthy subjects were rotated in one direction during 5 consecutive periods, and the duration of the latency time for the appearance of per-rotatory nystagmus was recorded. The case material was divided into 7 groups according to the strength of stimulus, i.e. 0.5, 0.75, 1.0, 1.5, 2.0, 3.0 and 5.0°/sec². The results show a fairly large absolute standard deviation in all groups. On the other hand, the relative standard deviation—expressed as the coefficient of variation—is much the same in all groups. The reproducibility is greater in the individual subject than in the group as a whole. Each subject is found to have a somewhat characteristic latency time level, which is not apparent if the study is confined to the whole group. It is suggested that these results are an expression of the normal variation in the mode of reaction of the vestibulo-ocular reflex arc.