Variability of the main sequence.

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Abstract

PURPOSE: This study investigated the relationship between amplitude and peak velocity of saccadic eye movements (the so-called main sequence) and the intra-individual variability of the main sequence. METHODS: Saccadic amplitudes and peak velocities were measured twice in 58 healthy subjects with an infrared reflection technique. RESULTS: Considerable intra-individual variability was found between the first and second recordings. CONCLUSIONS: Intra-individual variability of saccadic peak velocity affects the interpretation of changes in repeated recordings of peak velocities, such as before and after medication is administered. Furthermore, considerable intra-individual variability decreases the probability that statistically significant differences between patients and control subjects can be detected, especially when groups are small. Calculating the intraclass correlation coefficient allows the number of subjects in comparative studies to be determined.