Jerome Lecoq and Olivier J.-M. D. Coenen On the extraocular muscle pulleys: A modeling study. International Brain Research Organization Abstracts, 2003

Sony CSL authors: Olivier Coenen, Jérôme Lecoq

Abstract

A model is presented that suggests a new and active role for the extraocular muscle pulleys. Pulleys are connective tissue sleeves enveloping the extraocular muscle that change the muscle paths. Through a series of basic constraints and application of well known motor laws, the model predicts that the extraocular muscles need not ślip in the pulleys', but in fact that they can be attached to a fixed point onto the extraocular muscles. It is well known that in order to fulfill Donderś law during an eye movement starting from an arbitrary position, the axis of rotation must tilt out of the Listing plane by half the angle of the eyeś eccentricity (relative to primary position). This defines a new plane, commonly called the displacement plane. To describe the present model, we define an "action plane" as the plane containing the pulley and the mucle path from the pulley to the insertion point on the eye. The main hypothesis and prediction of the model is that the action plane, controlled by the pulleys, follows the displacement plane during eye movements. An interesting consequence is that the action plane moves during the eye movements so as to keep the contribution of each muscle constant during the eye movements, thereby simplifying considerably the motor control. The location of the pulleys were optimized in the model so as: to modify as little as possible the change in the slope of the extraocular muscle, to take into account a possible change of primary position across subjects in experimental data, to be more than 1 mm from the eye surface (Kono et al. IOVS 2002), and to remain at the same location on the extraocular muscle. The present model is compared to the common model that assumes an equidistant rule to determine the pulleysĺocation and is shown to provide a good match to experimental data (Kono et al. IOVS 2002). Major differences are expected between models for movement around secondary positions away from primary position. Videos showing the model pulleys displacement in three dimensions are available.

Keywords: extraocular, muscle, pulleys, model, modeling, Listing, Donder, law

BibTeX entry

@INPROCEEDINGS { lecoq:03a, AUTHOR="Jerome Lecoq and Olivier J.-M. D. Coenen", BOOKTITLE="International Brain Research Organization Abstracts", TITLE="On the extraocular muscle pulleys: A modeling study", YEAR="2003", }