EVOLUTION OF CONTROL-SYSTEM MODELS OF OCULAR ACCOMMODATION, VERGENCE AND THEIR INTERACTION

This paper reviews the evolution of inferential models describing ocul ar accommodation and vergence, which have been developed using the tec hniques of control engineering. The models are developed by inferring that the observed behaviour of the ocular systems could be produced by particular types of feedback control systems. The models are subseque ntly tested and improved by modifications resulting from the compariso n of model predictions with physiological experimentation. Current mod els of accommodation and vergence have had considerable success in des cribing both the steady-state and dynamic behaviours of the individual systems. However, controversy currently exists among researchers, par ticularly with respect to the composition of models that describe the interaction of the two systems.