The recording of three-dimensional eye position has become the accepte
d standard in oculomotor research. In this paper we review the mathema
tics underlying the representation of three-dimensional eye movements.
Rotation matrices, rotation vectors and quaternions are presented, an
d their relations described. The connection between search coils and r
otation matrices is explained, as well as the connection between eye p
osition and eye velocity. While examples of applications of the formul
as to vestibulo-ocular research are given, the methods and mathematica
l analyses are also useful for studying other motor systems.