DYNAMIC-MODEL OF THE VERGENCE EYE-MOVEMENT SYSTEM - SIMULATIONS USINGMATLAB SIMULINK/

A dynamic model of the vergence eye movement system was developed and simulated using MATLAB/SIMULINK. The model was based on a dual-mode dy namic model previously written in FORTRAN. It consisted of a fast open -loop component and a slow closed-loop component. The new model contai ned several important modifications. For example, in the fast componen t, a zero-order hole element replaced the sampler and the target traje ctory estimator in the earlier model to provide more stable and accura te responses. Also, a periodicity detector was added to automatically detect periodicity in the stimulus waveform. The stored periodic stimu lus, with a reduction in latency, was used to drive the fast component output. Moreover, a connection representing the efference copy signal was added from the fast component output to the disparity input to pr ovide an accurate estimate of the stimulus waveform. Further, Robinson 's model of the extraocular muscles replaced the earlier ?nd-order pla nt to provide more realistic muscle dynamics. The entire model, contai ning the fast and slow components, was simulated using a variety of st imuli such as pulses: positive and negative ramps, square-wave, and si ne-wave. The responses showed dynamic characteristics similar to exper imental results. Thus, this new MATLAB/SIMULINK program provides a rel atively easy-to-use, versatile, and powerful simulation environment fo r investigating the basic as well as clinical aspects of vergence dyna mics. Moreover, the simulation program has general characteristics tha t can be modified to represent other oculomotor systems such as the ve rsional and accommodation systems. This provides a framework for futur e investigation of dynamic interactions between oculomotor systems. (C ) 1998 Elsevier Science Ireland Ltd.