Quantitative analysis of pursuit eye movements by unidirectional target motion.

The effects of a change in target speed (10 degrees-100 degrees/s) and amplitude (10 degrees-80 degrees) on smooth pursuit eye movements were analyzed in normal subjects by moving a target unidirectionally. The limit of pursuit speed adaptation changed according to changes in the target amplitude, being about 40 degrees-50 degrees/s at a target amplitude of 40 degrees-80 degrees. The minimum target amplitude needed to induce rhythmic pursuit eye movements markedly increased from 3.7 degrees at 10 degrees/s to 55.0 degrees at 100 degrees/s. The relationship between the gain (the ratio of eye speed to target speed) and the pursuit time suggested that pursuit eye speeds may depend on the pursuit time rather than absolute target speeds and that the gain might become unity even at fast target speeds, provided the critical pursuit time is given.