Statistical Evaluation of Nystagmus in Cupulometry

Abstract

The literature on cupulometry shows inconsistent data as to (1) the magnitude of the time constant T₁; (2) the iníer-individual variation between subjects; (3) the difference between clockwise and counter-clockwise rotation, and (4) the linearity of the system. In our investigations, the nystagmus was measured after a start or a stop in angular velocity. All determinations were carried out six times for 5 subjects. The time constant T, was calculated from the slope of the decay of the slow-phase eye velocity. Statistical evaluation of the results showed: a test-retest variability which is greater than the inter-individual variability; significant inter-individual differences between subjects; mean values of T, for clockwise and counter-clockwise rotation of 13.2 (SD 1.4) and 12.8 (S.D. 1.7) sec, respectively; a significant difference of T₁ between clockwise and counter-clockwise rotations for individual subjects at the 95% level; no relation between T, and the amplitude of the step in angular velocity, and a linear increase of the maximum slow-phase eye velocity with the amplitude for velocities below 100 °/sec, whereas at higher velocities, saturation occurs.

Influence of Adaptation upon the Impulsive Time Constant of the Human Vestibulo-Ocular Reflex System

“…In a previous study [Boumans et al, 1980] the value of the response T [ was calculated from the impulse responses of the VOR system by the decay method (a), and found to be about 13 s. In the present study, Tj is calcu lated from the same data by the cupulometric method (b), and found to be about 11.7 s. These results bear out the theory as described in part I, where it is shown that when adaptation is present, method (b) gives a smaller apparent value of T! than method (a).…”

“…Nys tagmus reversal is denoted by: -= no reversal; ± = occasional reversal; + = reversal always occurs. Calculated by the decay method (a) the mean values of the response T i for CW and CCW stimulation are 13.2 ± 1.4 and 12.8 ± 1.7 s, respectively [Boumans et al, 1980].…”

“…The experimental data are the same as analysed in a previous study [Boumans et al, 1980). The reader is referred to this paper for the description of the stimulus, the recording technique, the subjects and the experimental procedure.…”

“…In a previous investigation [Boumans et al, 1980] the long time con stant T i of the response of the VOR system to an impulsive stimulation was calculated from the slope of the decay of slow phase eye velocity (SPV). The duration of the nystagmus and the possible presence of after-nystagmus were not dealt with.…”

Influence of Adaptation upon the Impulsive Time Constant of the Human Vestibulo-Ocular Reflex System

“…The value of the response T| can only be estimated from such a plot. This has been done by drawing a tangent to the upper curve in the time range where the slow phase eye velocity after an impulsive stimulation is measured: from about 6 to 26 s [Boumans et al, 1980], In figure 5 the estimated value of the response T i is found to be 13.8 s.…”