Properties of rapid eye movements.

Abstract

This chapter describes the metrics and kinematics of saccades and quick phases of nystagmus, including microsaccades and large eye-head saccades. Small saccades often display dynamic overshoot, predominantly in the abducting eye. Although the function of these overshoots is unclear, the return movement is saccadic in nature. The saccade kinematics can be quantified by stereotyped relations between amplitude, duration, peak eye velocity, and peak acceleration, which vary somewhat with the initial eye position and saccade direction (centripetal vs centrifugal), possibly due to ocular plant characteristics. Saccades in a structured light environment are considerably faster than when executed in total darkness, although the origin for this facilitation is not known. The horizontal and vertical components of slant saccades are coupled, approximately matching their durations, for which possible underlying neural mechanisms are discussed. The chapter closes with a cross-species comparison of saccade characteristics.