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Omer Naor, Esther Zemel, Eitan Kimmel, Shy Shoham; Holographic Acoustic Retinal Stimulation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5526.
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This study aims to explore the feasibility of a non-invasive acoustic retinal prosthesis for outer-retinal degeneration. Ultrasound (US) waves have recently been shown to stimulate neurons, a promising approach due to its non-invasiveness and technological ubiquity. For US to be used in a retinal prosthesis, it must first be shown to effectively and safely stimulate retinal neurons. In addition, inducing a unified visual percept also requires a strategy for generating patterned US fields.
We measured evoked potentials in anesthetized rats and in vitro, in response to short US pulse trains which were transmitted to the eye, as well as several control conditions. As a basic safety study we measured electroretinogram (ERG) responses from treated and un-treated eyes in a separate group of animals and observed histological sections of the retina.Patterns of US were generated using a phased acoustic array controlled using newly developed algorithms for holographic shaping of continuous US fields. The resulting acoustic patterns were studied through field simulations as well as thermometry measurements.
We show that accurate and uniform projection of arbitrarily shaped US fields can be achieved at rapid rates, suitable for online use in a prosthetic device. The in-vivo results indicate robust responses to US stimuli, significantly different from the controls and in compliance with the safety guidelines for ophthalmic US devices. In addition, both ERGs and histological sections revealed no damage to the retina.
The results demonstrate the efficacy and safety of the US approach to retinal stimulation, while the US field sculpting strategy lays the ground for simultaneous spatially distributed excitation patterns. Taken together, these results indicate the feasibility of an acoustic retinal prosthetic device for vision restoration.
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