Additional developments in oculomotor plant modeling.

Abstract

A new oculomotor plant is presented in this study using an updated third-order linear muscle model. The lateral and medial rectus muscle is modeled as a viscoelastic parallel combination connected to a parallel combination of active state tension generator, viscosity element and length tension elastic element. The eyeball is modeled as a sphere, connected to two parallel viscoelastic elements, connected in series. Each of the elements is linear. The static and dynamic properties of the muscle model are in good agreement with rectus muscle data. The length-tension characteristics of the model match the data within the operating region of the muscle. Simulation results for the muscle model yield hyperbolic shaped force-velocity curves that match the data very well. All parameters and initial conditions are estimated or directly measured from physiological data. The oculomotor plant is derived through direct programming state-space representation by Laplace variable analysis about the operating point or initial eye position. The form of the oculomotor plant makes this representation even more ideal than previous models for use in the development of more sensitive tests of oculomotor pathology and in the description of normal oculomotor function.