The dysrhythmia and the exponential constants of the postrotatory nystagmus qualities.

In 5 healthy individuals the postrotatory, exponential constants were estimated for each of the four nystagmus qualities, viz. the velocities and durations of fast and slow components. The residual spread (Sr) of each quality in a semilogarithmic plot was also determined. The value of the constant for postrotatory decay indicated a decrease of the velocity and an increase for the duration of the slow component, both with a significant difference between individuals, while for the corresponding values of the fast components no systematic change in the postrotatory reactions was indicated, nor any difference between individuals. The constant that corresponds to the value at maximum stimulus showed differences between individuals for each of the four nystagmus qualities, while Sr presented differences between individuals only for the two slow phase qualities. This technique to describe postrotatory nystagmus reactions by the two exponential constants for each of the four nystagmus qualities together with the residual spread for each of the qualities is intended for future 'on-line' nystagmus analysis.