Torsion is movement of the eye about its visual axis (note that we do not define it as about the front-back axis of the head). The term “rotatory nystagmus” is used interchangeably. There are many videos of torsional nystagmus on the site DVD and other pages on this site.

Torsional eye movements may be jerk or pendular.

When jerk, there are several methods of designating the direction that it jerks. We favor the unambiguous method of designating it by the direction that the top of the eye jumps - -left or right. Others use “clockwise” or “counterclockwise”, but the problem here is deciding whether the clock is to be considered on top of the patient's eye, or an external reference on the wall. We suggest just use the left/right nomenclature.

The most useful technique for seeing primary positional torsional nystagmus is fundoscopy.