Development of an Implantable Functional Electrical Stimulation System for the Treatment of Strabismus.

摘要

A system based on the functional electrical stimulation (FES) of extraocular muscles was developed to coordinate eye movements for the treatment of strabismus. This system would deliver a greater range of eye rotation with more predictability and consistency than state-of-the-art surgical treatments, such as muscle-transposition surgeries, while preserving the physiological muscle positions for the possibility of spontaneous recovery. The objectives of this research were to demonstrate the ability to control eye positions and conjugate movements using epimysial stimulation of an extraocular muscle and to use these preliminary efforts to advance the development of supporting technologies required to realize such a system.;Evoked open-loop eye deflections using epimysial stimulation of the cat lateral rectus (LR) were characterized for innervated and denervated muscles. The results demonstrated that epimysial stimulation of the normal and paralyzed feline LR could be used to generate adequate rotation of the eye (38° maximum rotation in innervated LR and 19° in paralyzed LR).;Open-loop experiments were then conducted in the monkey LR in order to develop a model for controller simulation. Open-loop epimysial stimulation of monkey LR evoked up to 17° of maximum eye rotation and a peak angular velocity of 210°/s. Based on this data, a first-order model was developed to relate applied electrical stimulation to eye rotation. Simulated results of two unilateral controllers (slave eye tracking to master eye) predicted that closed-loop control of eye alignment and coordination were possible.;In the closed-loop primate experiment, a proportional feedback controller was used to track a slave eye to the other master eye. The experiment demonstrated conjugate movement of the eyes (85-ms and 122-ms average delays for medial rectus and LR, respectively) and a consistent linear relationship between master and slave eyes.;Although adequate eye rotations and conjugate eye movements were not demonstrated concurrently, demonstrations in separate studies in the same species (Rhesus macaque) suggest that an eye-coordination system based on epimysial stimulation of an extraocular muscle could be a feasible approach to the treatment of strabismus.