Purchase this article with an account.
J. O. Phillips, L. Ling, A. Fuchs, C. Kaneko, S. Bierer, K. Nie, T. Oxford, J. Rubinstein; Evaluation of a Chronically Implanted Prosthesis to Parametrically Control Nystagmic Eye Movements. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4761.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
We evaluated the efficacy and mechanism of a chronically implanted prosthesis for the control of vestibular nystagmus direction, velocity and waveform using evoked potential recording, recorded eye movements, and single unit neural recording.
4 Rhesus monkeys were implanted with a semicircular canal stimulator based on a Nucleus Freedom cochlear implant. The device had three stimulation leads, with three independent stimulation sites each, and was designed and constructed for chronic human implantation. The device was implanted between the membranous and bony labyrinth adjacent to the ampulla of multiple canals. Vestibular function was assessed with en-bloc rotation in the plane of the implanted canal. Hearing was assessed with ABR. Nystagmus was assessed with surgically implanted scleral coils during electrical stimulation in the dark, in the light, and during rotation and optokinetic stimulation. Neural function was assessed at the end organ with compound action potential recording, and centrally with single unit recording.
Natural vestibular and hearing function were intact in 3 of 4 monkeys. Electrical stimulation of individual canals produced directionally appropriate eye movements largely in the plane of the implanted canal at thresholds ≤50uA. Increases in stimulation current and frequency produced increasing slow phase velocity of eye movement. Stimulation could be used produce specific nystagmus waveforms, modulate the gain of the VOR response, or eliminate vestibular nystagmus or optokinetic afternystagmus. Increasing current increased the amplitude of the evoked compound action potential peripherally, and of the field potential in the vestibular nucleus. Individual neurons followed high frequency electrical stimulation reliably at 2X threshold. Most neurons were activated only by electrical stimulation of one canal, typically the canal aligned with their best rotation direction.
Electrical stimulation with a minimally invasive chronic implant activates specific directional channels for nystagmus and can be modulated to control the resulting eye velocity and waveform. This device may have promise in controlling or eliminating some forms of jerk nystagmus in humans.
This PDF is available to Subscribers Only