DETERMINATION OF OCULAR TORSION BY MEANS OF AUTOMATIC PATTERN-RECOGNITION

A new, automatic method for determination of human ocular torsion (OT) was developed based on the tracking of iris patterns in digitized vid eo images, Instead of quantifying OT by means of cross-correlation of circular iris samples, a procedure commonly applied, this new method a utomatically selects and recovers a set of 36 significant patterns in the iris by the technique of template matching as described by In den Haak et al. [16], Each relocated landmark results in a single estimate of the torsion angle. A robust algorithm estimates OT from this total set of individually determined torsion angles, thereby largely correc ting for errors which may arise due to misjudgement of the rotation ce nter, The new method reproduced OT in a prepared set of images of an a rtificial eye with an accuracy of 0.1 degrees, In a sample of 256 imag es of human eyes, a practical reliability of 0.25 degrees was achieved , To illustrate the method's usefulness, an experiment is described in which ocular torsion was measured during two dynamic conditions of wh ole-body roll, namely during sinusoidally pendular motion about either an earth horizontal or earth vertical axis (that is ''with'' and ''wi thout'' otolith stimulation, respectively).