Simulating eye-head coordination during smooth pursuit using an ocular biomechanic model

The main objective of all eye movements is to keep the image of the object of interest focused. Head motion makes this objective more complex. However, the vestibular system is responsible for eye movement that compensate head motion. Simulating and analysing eye movement in coordination with head and neck movements is useful for assessing visual system contribution to discomfort in different tasks especially related to motion such as simulation sickness. In this paper, we present an ocular biomechanic model integrated into a head and neck model and used to simulate and analyse eye-head coordination movement during smooth pursuit. The proposed model is based on the physiological and the kinematics properties of the human eye provided from clinical trials performed by Robinson and Collins and also magnetic resonance imaging studies. The model incorporates six extraocular muscles (EOMs) and their connective tissues, known as pulleys. The pulleys are modelled as moving points on the muscle path according to the Active Pulley Hypothesis (APH) provided by Kono et al. Dynamic simulations of smooth pursuit with head movement is presented. The model achieved root mean square error (RMSE) of 0.77°, 0.29°and 0.14°for the horizontal, vertical and torsional rotation angles. It can be further used to simulate and analyse the vestibulo-ocular reflex of the eye.