DYNAMICAL-SYSTEMS ANALYSIS - A NEW METHOD OF ANALYZING CONGENITAL NYSTAGMUS WAVE-FORMS

Congenital nystagmus is an oculomotor disorder in which fixation is di srupted by rhythmical, bilateral involuntary oscillations. Clinically these eye movements have been described with some degree of success in terms of their peak-to-peak amplitude, frequency, mean Velocity and w aveform shape. However, it has not proved possible to diagnose any und erlying pathology from the nystagmus characteristics. Here, we propose a new approach to understanding the nystagmus using dynamical systems theory. Our approach is based on the use of delay embedding technique s, which allow one to relate a time series of scalar observations to t he state space dynamics of the underlying dynamical system. Using this approach we quantify the dynamics of the nystagmus in the region of f oveation and present evidence to suggest that it is low-dimensional an d deterministic. Our results put new constraints on acceptable models of nystagmus and suggest a way to make a closer link between data anal ysis and model development. This approach raises the hope that techniq ues originally developed to stabilise chaotic systems, by using small perturbations, may prove useful in the control of nystagmus.