Ocular torsion quantification with video images.

The present paper describes a technique to quantify eye rotations about the visual axis (ocular torsion). Two digitized polar transformed images of the iris are displayed on a video monitor in order to facilitate a visual comparison and manual interaction. Emphasis is placed on error analysis and the method's simplicity when applied to static ocular torsion measurement. The implementation, applying averaging over ocular torsion determined in partitioned iris images, yields a theoretical resolution of 5' of arc. In a control experiment with an artificial eye, the accuracy showed to be better than 14' of arc. In practice, the measuring device was validated with the data from the literature by means of an experiment about ocular torsion in humans during tilt and hypergravity conditions (up to 3 g).